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Sample records for austempered spheroidal graphite

  1. Characterisation of austempered spheroidal graphite aluminium cast iron

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    Boutorabi, S.M.A. [Iran Univ. of Science and Technology, Tehran (Iran, Islamic Republic of). Dept. of Metallurgy and Materials

    1997-06-01

    The micro constituents of austempered spheroidal graphite aluminium cast iron were investigated. The heat tinting, special etching and microhardness measurement techniques were used. The results showed that the colour of each micro constituents and the hardness values in austempered ductile iron depend on the carbon content of each phase. The above techniques were supported by using an special etching which showed similar differences in each phase. It was shown that the heat tinting and special etching are reliable tools to characterise the complex matrix of ADI. The microhardness data supported interestingly the colour changes in above technique. (orig.)

  2. Impact characteristics of austempered spheroidal graphite cast steel. Austemper kyujo kokuen chuko no shogeki tokusei

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    Takahashi, T.; Tada, S.; Abe, T. (Government Industrial Research Institute, Tohoku, Sendai (Japan))

    1993-08-25

    Austempered ductile cast iron (ADI) has excellent mechanical properties both in strength and toughness, but the Young's modulus of ADI is lower than that of steel because ADI contains much graphite. In order to obtain better mechanical properties than ADI, spheroidal graphite cast steel containing less graphite by volume was austempered. The Young's modulus of austempered spheroidal graphite cast steel (AGS) was 200 GPa, which was comparable to steel. The retained austenite volume of the sample containing 2.4% Si varied with the austempering conditions, but that of the sample containing 1.4% Si decreased in a shorter austempered time. As a result, it was found that Si affects stability of the retained austenite. Charpy impact value increased with increasing the retained austenite volume when the volume was above 15%. The impact value of AGS with 40% retained austenite was over twice as large as that of ADI austempered under the same conditions. 21 refs., 8 figs., 1 tab.

  3. Effect of bainite transformation and retained austenite on mechanical properties of austempered spheroidal graphite cast steel

    Science.gov (United States)

    Takahashi, Toshio; Abe, Toshihiko; Tada, Shuji

    1996-06-01

    Austempered ductile iron (ADI) has excellent mechanical properties, but its Young's modulus is low. Austempered spheroidal graphite cast steel (AGS) has been developed in order to obtain a new material with superior mechanical properties to ADI. Its carbon content (approximately 1.0 pct) is almost one-third that of a standard ADI; thus, the volume of graphite is also less. Young's modulus of AGS is 195 to 200 GPa and is comparable to that of steel. Austempered spheroidal graphite cast steel has an approximately 200 MPa higher tensile strength than ADI and twice the Charpy absorbed energy of ADI. The impact properties and the elongation are enhanced with increasing volume fraction of carbon-enriched retained austenite. At the austempering temperature of 650 K, the volume fraction of austenite is approximately 40 pct for 120 minutes in the 2.4 pct Si alloy, although it decreases rapidly in the 1.4 pct Si alloy. The X-ray diffraction analysis shows that appropriate quantity of silicon retards the decomposition of the carbon-enriched retained austenite. For austempering at 570 K, the amount of the carbon-enriched austenite decreases and the ferrite is supersaturated with carbon, resulting in high tensile strength but low toughness.

  4. Effect of bainite transformation and retained austenite on mechanical properties of austempered spheroidal graphite cast steel

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    Takahashi, Toshio; Abe, Toshihiko; Tada, Shuji [Tohoku National Industrial Research Inst., Sendai (Japan). Materials Engineering Div.

    1996-06-01

    Austempered ductile iron (ADI) has excellent mechanical properties, but its Young`s modulus is low. Austempered spheroidal graphite cast steel (AGS) has been developed in order to obtain a new material with superior mechanical properties to ADI. Its carbon content (approximately 1.0 pct) is almost one-third that of a standard ADI; thus, the volume of graphite is also less. Young`s modulus of AGS is 195 to 200 GPa and is comparable to that of steel. Austempered spheroidal graphite cast steel has an approximately 200 MPa higher tensile strength than ADI and twice the Charpy absorbed energy of ADI. The impact properties and the elongation are enhanced with increasing volume fraction of carbon-enriched retained austenite. At the austempering temperature of 650 K, the volume fraction of austenite is approximately 40 pct for 120 minutes in the 2.4 pct Si alloy, although it decreases rapidly in the 1.4 pct Si alloy. The X-ray diffraction analysis shows that appropriate quantity of silicon retards the decomposition of the carbon-enriched retained austenite. For austempering at 570 K, the amount of the carbon-enriched austenite decreases and the ferrite is supersaturated with carbon, resulting in high tensile strength but low toughness.

  5. Application of successive austempering process to spheroidal graphite cast iron produced by inmold process. Inmold ho de seizoshita kyujo kokuen chutetsu eno chikuji austemper ho no tekiyo

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    Oide, T.; Ahmadabadi, M.; Kawashima, S. (Tohoku University, Sendai (Japan). Faculty of Engineering)

    1994-06-25

    Application of successive austempering process to the iron produced by inmold process leads to much higher graphite nodule count in the structure than the other spheroidizing methods. In this study, to improve the toughness of spheroidal graphite cast iron produced by inmold process, successive austempering process was applied to austemper ductile iron (ADI) production. Both hardenability and austemperability of the iron could be controlled with Mn alloying through the two-stage austempering at high and low temperatures. Higher retained austenite volume fraction and lower untransformed austenite volume fraction were obtained in the most suitable duplex upper and lower bainitic structure. It was confirmed that the impact energy of ADI treated by successive austempering process was remarkably much higher than the conventional austempering processes. In this process, an excellent value of toughness was obtained by selecting a combination of holding temperature and holding time, strictly. 17 refs., 10 figs., 2 tabs.

  6. Fractal Model of the Spheroidal Graphite

    Institute of Scientific and Technical Information of China (English)

    Z.Y.HE; K.Z.HWANG

    1996-01-01

    In this paper,a fractal model about the microstructure of spheroidal-graphite is presented through the research on the surface form and the analysis to microregion.The fractal dimension is calculated and the forming mechanism is also discussed.

  7. Effect of austempering temperature and time on the kinetics and microstructure of austempered compacted graphite cast irons; Einfluss von Zwischenstufenverguetungstemperatur und -zeit auf die Kinetik und die Mikrostruktur von zwischenstufenverguetetem, Gusseisen mit Vermiculargraphit

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    Teymourian, Mehdi [LMI Co., Tehran (Iran, Islamic Republic of). Casting Dept.; Boutorabi, Seyed Mohammad Ali [Iran Univ. of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of). Center of Excellence for Advanced Materials

    2012-07-01

    After starting the austempering nucleation of bainitic ferrite was observed within a very short time. Samples that austempered for 2 min. showed martensite in the microstructure. By increasing the austempering time from 30 min to 90 min the retained austenite decomposes and X-ray diffraction observations revealed the greatest volume fraction of retained austenite up to 17.3 and 23.8 percent when austempered for 30 min. Micro-hardness of the bainitic Verbesferrite increased up to 370 and 500 HV and micro-hardness of the retained austenite increased up to 300 and 400 HV at the austempering temperatures of 300 C and 400 C respectively. In comparison to austempered ductile iron, the austempered compacted graphite cast iron shows higher rate of bainitic reaction. Bainite formation driving force and consequently the rate of austempering process are higher in compacted graphite cast irons. (orig.)

  8. Valence electron theory of graphite spheroidizing in primary crystallization

    Institute of Scientific and Technical Information of China (English)

    刘志林; 孙振国; 李志林

    1995-01-01

    Bond-length-difference (BLD) analysis results show that austenrte and cementite containing Mg, Zr. S have very different valence electron structures from Fe -C austenite and cementite. We find that this difference is the tie of absorption hypothesis, surface tension hypothesis, undercooling hypothesis in graphite spheroidizing theory. By using "the model of valence electron theory of drag-like effect" in our previous paper in crystallization theory, the spheroidizing effect of Mg and Zr and the anti-spheroidizing effect of S can be explained with the valence electron structure data of phases. Therefore, electron theory of graphite spheroidizing can be advanced.

  9. The studies of nodular graphite cast iron early stages austempering

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    A. Krzyńska

    2008-12-01

    Full Text Available The results of early stage of ductile cast iron austempering are presented. The aim of the investigations was to look closer into the structure – mechanical properties relationships of this very attractive cast material. The experiment was carried out with enriched with Cu EN-GJS-500-7 grade ductile iron. The specimens were first solution heat treated 1 hour in 910oC and then isothermally quenched for different time in molten tin at the temperature 275oC. The mechanical properties of as cast and heat treated specimens were tested to evaluate tensile Rm and yield strength R p, 0.2 and elongation A5. Additionally hardness measurements were carried out using Brinell-Rockwell method. Structure of the specimens both as cast and after austempering was studied using conventional light microscopy. Moreover, scanning electron microscopy (SEM was applied for fracture surface observations. It was concluded that short time low temperature austempering lead to formation martensitic microstructure characterized by very high hardness with almost zero ductility. The lack of ductility make the material very sensitive to any structure defects which work as a stress concentrators which strongly influence the strength of heat treated ductile iron specimens.

  10. The studies of nodular graphite cast iron early stages austempering

    OpenAIRE

    A. Krzyńska; M. Kaczorowski

    2008-01-01

    The results of early stage of ductile cast iron austempering are presented. The aim of the investigations was to look closer into the structure – mechanical properties relationships of this very attractive cast material. The experiment was carried out with enriched with Cu EN-GJS-500-7 grade ductile iron. The specimens were first solution heat treated 1 hour in 910oC and then isothermally quenched for different time in molten tin at the temperature 275oC. The mechanical properties of as cast ...

  11. Influence of the Mn content on the kinetics of austempering transformation in compacted graphite cast iron

    Science.gov (United States)

    Desimoni, J.; Mercader, R. C.; Laneri, K.; Gregorutti, R.; Sarutti, J. L.

    1999-11-01

    Mossbauer spectroscopy has been used to monitor the kinetics of austempering transformation in two compacted graphite (CG) cast irons alloyed with 0.11 and 0.58 wt pct of Mn, respectively. The phase relations were analyzed in terms of the Johnson-Mehl’s equation, determining the kinetics parameters n (time exponent) and k (constant rate of the transformation). The values obtained were n=1.4 and k=7.47 × 10-3 s-1 for the low-Mn alloy, and n=2.2 and k=3.9×10-3 s-1 for the high-Mn alloy. These results, which reveal a faster kinetics for the low-Mn alloy, are coherent with metallographic observations, and the driving force obtained through the determination of the austenite carbon concentration that was determined from the Mossbauer data using the Genins model for the Fe-C configurations in the fcc lattice. The kinetics parameters are further compared to those obtained in austempered ductile iron (ADI), by analyzing the graphite morphology influence on the austempering transformation.

  12. Influence of the Mn content on the kinetics of austempering transformation in compacted graphite cast iron

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    Desimoni, J.; Gregorutti, R.; Laneri, K.; Sarutti, J.L.; Mercader, R.C.

    1999-11-01

    Moessbauer spectroscopy has been used to monitor the kinetics of austempering transformation in two compacted graphite (CG) cast irons alloyed with 0.11 and 0.58 wt pct of Mn, respectively. The phase relations were analyzed in terms of the Johnson-Mehl's equation, determining the kinetics parameters n (time exponent) and k (constant rate of the transformation). The values obtained were n = 1.4 and k = 7.47 x 10{sup {minus}3} s{sup {minus}1} for the low-Mn alloy, and n = 2.2 and k = 3.9 x 10{sup {minus}3} s{sup {minus}1} for the high-Mn alloy. These results, which reveal a faster kinetics for the low-Mn alloy, are coherent with metallographic observations, and the driving force obtained through the determination of the austenite carbon concentration that was determined from the Moessbauer data using the Genins model for the Fe-C configurations in the fcc lattice. The kinetics parameters are further compared to those obtained in austempered ductile iron (ADI), by analyzing the graphite morphology influence on the austempering transformation.

  13. Mathematical modeling of localized melting around graphite nodules during laser surface hardening of austempered ductile iron

    Science.gov (United States)

    Roy, A.; Manna, I.

    2000-10-01

    An attempt has been made to mathematically predict the optimum conditions of laser surface hardening (LSH) of austempered ductile iron (ADI) that can ensure a predominantly martensitic microstructure and preclude partial/complete dissolution of graphite nodules in the laser hardened zone during laser irradiation. The exercise involves prediction of the thermal profile (using the Ashby and Easterling model), and consequently, the carbon diffusion profile around the graphite nodules at different depths from the surface for the given conditions of LSH. Microstructural investigations have been carried out by optical and scanning electron microscopy to study the morphology, shape and width of the partially/completely melted graphite nodules as a function of the LSH parameters. Finally, the predicted maximum width of the melted zone around the graphite nodules is compared with the relevant experimental data to validate the proposed model.

  14. Influence of casting size and graphite nodule refinement on fracture toughness of austempered ductile iron

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    Lee, S.C.; Hsu, C.H.; Chang, C.C.; Feng, H.P. [Tatung Inst. of Tech., Raipei (Taiwan, Province of China). Dept. of Materials Engineering

    1998-10-01

    Casting size affects the solidification cooling rate and microstructure of casting materials. Graphite nodules existing in the structure of ductile iron are an inherent and inert second phase that cannot be modified in subsequent heat-treatment processing. The matrix and the fineness of the second phase undoubtedly have some impact on the fracture toughness of the as-cast material, as does the subsequent heat treatment, as it alters the microstructure. This research applied austempering heat treatment to ductile iron of different section sizes and graphite nodule finenesses. The influence of these variables on the plane strain fracture toughness (K{sub IC}) of the castings so treated was compared to that of the as-cast state. Metallography, scanning electron microscopy (SEM), and X-ray diffraction analysis were performed to correlate the properties attained to the microstructural observation.

  15. Effect of Graphite Nodule Diameter on Water Embrittlement of Austempered Ductile Iron

    Institute of Scientific and Technical Information of China (English)

    CAI Qi-zhou; WEI Bo-kang; TANAKA Yuichi

    2005-01-01

    Effects of graphite nodule diameter on the water embrittlement of austempered ductile iron (ADI) is studied. The water embrittlement mechanism is discussed. Due to water adhesion, local embrittlement occurs on the surface of ADI specimen, resulting in early fracture and significant reduction in tensile strength and elongation. The water embrittlement is the cracking of stress induced martensite formed during tensile deformation caused by hydrogen diffusion decomposed from water and as a result tensile strength and elongation of ADI are remarkably reduced. The segregation of alloying elements in ductile iron is weakened with decreasing nodule diameter, reducing the residual austenite in grain boundaries, then decreasing the amount of stress induced martensite during tensile plastic deformation and finally restraining ADI water embrittlement.

  16. Effects of Graphite Form and Amount on Performance of Austempered Ductile Iron%石墨形态和数量对奥-贝球铁性能的影响

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    许太平; 徐伟; 蔡彦强; 贾连杰

    2013-01-01

    For the austempered ductile iron as required by tensile strength ≥1200MPa, elongation after fracture≥1% and energy absorption (sample without notch)≥35J, if its spheroidization rate is lower than level 3, the spheroidal graphite is thicker than level 6 and its amount per mm2 is less than 180, its mechanical performance after isothermal treatment will be difficult to suit the specification requirements.%对于要求抗拉强度≥1200MPa;断后伸长率逸1%;吸收能量(无缺口试样)≥35J的奥-贝球铁,如果其球化率差于3级,球墨粗于6级且每平方毫米球墨少于180个,等温处理后的力学性能不易达到规范要求。

  17. Effect of graphite nodule count and Mn content on successive austempering process of austempered ductile iron; ADI no chikuji austemper ho ni oyobosu kokuen tsubusu to Mn ryo no eikyo

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    Oide, T.; Ahmadabadi, M.; Saito, M. [Tohoku University, Sendai (Japan). Faculty of Engineering

    1995-02-25

    Shock test was executed for a test piece where the combination of a wide range of austempering conditions was selected and the effective graphite nodule count in the successive austempering process method, the range of Mn amount, etc. were discussed. The low and high graphite nodule counts of sample were 82 - 114 and 229 - 364 piece/mm{sup 2}, respectively. The low and high Mn were 0.26 - 0.65 % and 0.96 - 1.05 %, respectively. The heat treatment cycle was retained to be 1173K, 648K, and 588K in argon gas atmosphere. The Sharpy shock test and organization observation were performed for each test piece, thus revealing that a higher toughness value than that obtained by normal treatment could be obtained by the HLAT method; the better the graphite nodulation count was, the higher the toughness was; it was effective that the Mn was approximately 0.6 %; the influence given to the shock energy value was extremely larger by residual austenite volume than the untransformed austenite module. 7 refs., 12 figs., 2 tabs.

  18. Formation of microstructures in the spheroidal graphite cast iron

    Science.gov (United States)

    Wang, S.; Daloz, D.; Bruneseaux, F.; Lesoult, G.

    2012-01-01

    Pipeline systems for hydraulic networks are obtained via centrifugal casting of spheroidal graphite cast iron. The very high cooling rate that is achieved in the skin of the product can sometimes lead to carbide instead of graphite in cast iron. An experimental device has been built in the laboratory that allows reproducing the extreme thermal conditions encountered during formation of skin of centrifugally cast pipes. Liquid metal droplets fall on a cold substrate. Rapid directional solidification occurs. The temperature evolution of the lower surface of the droplet is recorded during the very first moment of the solidification (t cast state and the heat-treated state. They are compared to the centrifugally cast ones. A model of directional solidification of cast iron under a very large temperature gradient has been built. It allows explaining the transition from stable to metastable micro structure that was observed in the products and reproduced in the laboratory samples.

  19. Nucleation and Growth of Graphite in Eutectic Spheroidal Cast Iron: Modeling and Testing

    Science.gov (United States)

    Carazo, Fernando D.; Dardati, Patricia M.; Celentano, Diego J.; Godoy, Luis A.

    2016-06-01

    A new model of graphite growth during the continuous cooling of eutectic spheroidal cast iron is presented in this paper. The model considers the nucleation and growth of graphite from pouring to room temperature. The microstructural model of solidification accounts for the eutectic as divorced and graphite growth rate as a function of carbon gradient at the liquid in contact with the graphite. In the solid state, the microstructural model takes into account three stages for graphite growth, namely (1) from the end of solidification to the upper bound of intercritical stable eutectoid, (2) during the intercritical stable eutectoid, and (3) from the lower bound of intercritical stable eutectoid to room temperature. The micro- and macrostructural models are coupled using a sequential multiscale approach. Numerical results for graphite fraction and size distribution are compared with experimental results obtained from a cylindrical cup, in which the graphite volumetric fraction and size distribution were obtained using the Schwartz-Saltykov approach. The agreements between the experimental and numerical results for the fraction of graphite and the size distribution of spheroids reveal the importance of numerical models in the prediction of the main aspects of graphite in spheroidal cast iron.

  20. Influence of boron on ferrite formation in copper-added spheroidal graphite cast iron

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    Ying Zou

    2014-07-01

    Full Text Available This paper reviews the original work of the authors published recently, describing the influence of B on the matrix of the Cuadded spheroidal graphite cast iron. The effect of Cu has been corrected as a ferrite formation promoter in the matrix of the grey cast iron by the usage of high-purity material. Also, this paper focuses on the ferrite formation and the observation of the Cu distribution in the B-added and B-free Cu-containing spheroidal graphite cast iron. The Cu film on the spheroidal graphite can be successfully observed in the B-free sample using a special etching method. However, in the B-added sample, no Cu film could be found, while the secondary graphite was formed on the surface of the spheroidal graphite. The interaction between B and Cu is stressed as a peculiar phenomenon by the employment of a contrast experiment of B and Mn. The heat treatment could make Cu precipitate more significantly in the eutectic cells and in the matrix in the form of large Cu particles because of the limited solubility of Cu.

  1. Wear Behavior of Austempered Ductile Iron with Nanosized Additives

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    J. Kaleicheva

    2014-03-01

    Full Text Available The microstructure and properties of austempered ductile iron (ADI strengthened with nanosized addtives of titanium nitride + titanium carbonitride (TiN + TiCN, titanium nitride TiN and cubic boron nitride cBN are investigated. The TiN, TiCN and cBN, nanosized particles are coated by electroless nickel coating EFTTOM-NICKEL prior to the edition to the melt. The spheroidal graphite iron samples are undergoing an austempering, including heating at 900 оС for an hour, after that isothermal retention at 280 оС, 2 h and 380 оС, 2h. The metallographic analysis by optical metallographic microscope GX41 OLIMPUS and hardness measurements by Vickers Method are performed. The structure of the austempered ductile iron consists of lower bainite and upper bainite.Experimental investigation of the wear by fixed abrasive are also carried out. The influence of the nanosized additives on the microstructure, mechanical and tribological properties of the austempered ductile irons (ADI is studied.

  2. Anodic Dissolution of Spheroidal Graphite Cast Iron with Different Pearlite Areas in Sulfuric Acid Solutions

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    Yoshikazu Miyata

    2013-01-01

    Full Text Available The rate equation of anodic dissolution reaction of spheroidal graphite cast iron in sulfuric acid solutions at 298 K has been studied. The cast irons have different areas of pearlite. The anodic Tafel slope of 0.043 V decade−1 and the reaction order with respect to the hydroxyl ion activity of 1 are obtained by the linear potential sweep technique. The anodic current density does not depend on the area of pearlite. There is no difference in the anodic dissolution reaction mechanisms between pure iron and spheroidal graphite cast iron. The anodic current density of the cast iron is higher than that of the pure iron.

  3. Wearing Quality of Austenitic, Duplex Cast Steel, Gray and Spheroidal Graphite Iron

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    S. Pietrowski

    2012-04-01

    Full Text Available The current work presents the research results of abrasion wear and adhesive wear at rubbing and liquid friction of new austenitic, austenitic-ferritic (“duplex” cast steel and gray cast iron EN-GJL-250, spheroidal graphite iron EN-GJS-600-3, pearlitic with ledeburitic carbides and spheroidal graphite iron with ledeburitic carbides with a microstructure of the metal matrix: pearlitic, upper bainite, mixture of upper and lower bainite, martensitic with austenite, pearlitic-martensitic-bainitic-ausferritic obtained in the raw state. The wearing quality test was carried out on a specially designed and made bench. Resistance to abrasion wear was tested using sand paper P40. Resistance to adhesive wear was tested in interaction with steel C55 normalized, hardened and sulfonitrided. The liquid friction was obtained using CASTROL oil. It was stated that austenitic cast steel and “duplex” are characterized by a similar value of abrasion wear and adhesive wear at rubbing friction. The smallest decrease in mass was shown by the cast steel in interaction with the sulfonitrided steel C55. Austenitic cast steel and “duplex��� in different combinations of friction pairs have a higher wear quality than gray cast iron EN-GJL- 250 and spheroidal graphite iron EN-GJS-600-3. Austenitic cast steel and “duplex” are characterized by a lower wearing quality than the spheroidal graphite iron with bainitic-martensitic microstructure. In the adhesive wear test using CASTROL oil the tested cast steels and cast irons showed a small mass decrease within the range of 1÷2 mg.

  4. Rolling contact fatigue strength of successive austempered ductile cast iron; Chikuji austemper shori kyujo kokuen chutetsu no korogari hiro kyodo

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    Fujita, T. [Yamaguchi University, Yamaguchi (Japan). Faculty of Engineering; Ogi, K. [Kyushu University, Fukuoka (Japan). Faculty of Engineering; Sawamoto, A. [Yamaguchi Univ., Yamaguchi (Japan). Faculty of Education

    1998-04-25

    The holding time of austempered spheroidal graphite cast iron material is allowed to vary in heat treatment especially at the lower bainite transformation zone during the process for the preparation of specimens different from each other in the amount of {gamma}-pool, and the specimens are tested for their rolling contact fatigue strength. The effects of the amount of {gamma}-pool, roughness of the bainite structure, and work-hardening, on the rolling fatigue strength are also studied. Findings obtained as the result of experiment are stated below. In the case of an austempered ductile cast iron specimen containing a {gamma}-pool amount that occupies a high rate of 6.52%, the rolling fatigue withstanding limit exhibits a relatively high level of 1310MPa, which becomes approximately 1245MPa when the holding time is extended in the lower bainite transformation zone. The limit rises to approximately 1320MPa at a stage where the {gamma}-pool virtually disappears. In a successive austempering treatment process that aims at improving on machinability and at allowing sufficient fatigue strength to be maintained, it is necessary to allow the holding time in the bainite zone to be long enough for the {gamma}-pool to disappear and for the lower bainite structure to grow sufficiently. 5 refs., 10 figs., 4 tabs.

  5. Un-lubricated sliding wear performance of unalloyed austempered ductile iron under high contact stresses

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    Zimba, J.; Samandi, M.; Yu, D.; Chandra, T.; Navara, E.; Simbi, D.J

    2004-08-15

    The dry sliding wear behaviour of unalloyed austempered ductile iron (ADI) was studied in a reciprocating tribotester using contact loads in the range 40-140 N. The results obtained show that austempering in the temperature range 325-375 deg. C significantly improves the tribological properties of the unalloyed spheroidal graphite iron. The friction coefficient was reduced by a factor of ten (10) with the wear resistance increasing by several orders of magnitude. The improvement in wear performance was attributed to: the lubricity inherent the graphite nodules, the increase in initial hardness brought about by the ausferrite structure, and the work hardening of the surface as retained austenite is transformed to martensite by plastic deformation, and in the process reducing considerably the sensitivity of the specific wear rate to loading. Optical, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) results pertaining to the wear tracks suggest that two main wear mechanisms are responsible for material removal in the unlubricated sliding wear of ADI, namely, plastic yielding and oxidation, with the latter producing hard oxide particles that act as abrasives. Massive plastic yielding followed by delamination and sometimes oxidation accounts for material loss in the much softer as cast ductile spheroidal graphite iron.

  6. Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron have been studied, considering the parameters of carbon equivalent, inoculation, casting modulus, mold type (green or dry) and pouring temperature within specific ranges of these variables. Based on the orthogonal experiments, the metallurgical and processing parameters of the minimum casting shrinkage and the maximum casting shrinkage were obtained, and the effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron castings were discussed. Finally,two regression equations relating these variables to the formation of shrinkage porosity were derived based upon the orthogonal experiments conducted.

  7. Formation of VC- composites surface layers on spheroidized graphite cast iron by laser surface cladding process

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    Essam R.I. Mahmoud

    2015-01-01

    Full Text Available Spheroidal graphite cast iron was laser cladded with VC powder of 44-53 μm particle size using YAG Fiber laser at 500, 1000, and 1500 W processing power and fixed travelling speed of 4 mm/s. The powder was preplaced on the surface of the specimens with 0.5 mm thickness. To prevent the oxidation, argon gas was used as a shielding gas. After the treatment, three zones were resulted: build-up (cladding, fusion, and heat affected zones. The build-up zone was a composite structure consisted of VC particles/dendrites dispersed in a matrix of martensite, carbides and ledeburite structure. At 500 W, most of the VC particles were appeared as their original large size. When the laser power was increased to 1000 W or more, the VC particles were melted and then re-solidified in the form of fine dendrites. The surface hardness of the cladded area was remarkably improved. As the distance from the free surface increases, the hardness decreases. The average hardness value at the surface treated by 500 W was about 710 HV (3 times of the hardness of substrate, while it reached to about 1340 HV and 1520 HV at powers of 1000 W and 1500 W, respectively. The wear resistance of the laser treated samples was improved at all investigated laser processing powers, especially at 1000W and 1500 W.

  8. Grinding Wear Behaviour of Stepped Austempered Ductile Iron as Media Material During Comminution of Iron Ore in Ball Mills

    Science.gov (United States)

    Raghavendra, H.; Bhat, K. L.; Udupa, K. Rajendra; Hegde, M. M. Rajath

    2011-01-01

    An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media material for grinding iron ore in a ball mill. Spheroidal graphite (S.G) iron balls are austenitised at 900° C for 60 minutes and given stepped austempering treatment at 280° C for 30 minutes and 60 minutes followed by 380° C for 60 minutes in each case. These materials are characterised by measuring hardness, analysing X-ray diffraction (X-RD), studying microstructure using optical and scanning electron microscope (SEM). Grinding wear behaviour of these materials was assessed for wear loss in wet condition at different pH value of the mineral slurry and found that the wear rate of grinding media material decreases with increase in pH of the slurry. The wear resistance of ADI balls were compared with forged En31 steel balls and found that the stepped austempered ductile iron is superior to forged En31 steel balls.

  9. Microstructure and Wear Behavior of TiC Coating Deposited on Spheroidized Graphite Cast Iron Using Laser Surfacing

    Directory of Open Access Journals (Sweden)

    E. R. I. Mahmoud

    2014-10-01

    Full Text Available Spheroidal graphite cast iron was laser cladded with TiC powder using a YAG fiber laser at powers of 700, 1000, 1500 and 2000 W. The powder was preplaced on the surface of the specimens with 0.5 mm thickness. Sound cladding and fusion zones were observed at 700, 1000 and 1500 W powers. However, at 2000 W, cracking was observed in the fusion zone. At 700 W, a build-up zone consisted of fine TiC dendrites inside a matrix composed of martensite, cementite (Fe3C, and some blocks of retained austenite was observed. In this zone, all graphite nodules were totally melted. In the fusion zone, some undissolved and partially dissolved graphite nodules appeared in a matrix containing bainite, ferrite, martensite and retained austenite. At 1500 W, the fusion zone had more iron carbides and ferrite, and the HAZ consisted of martensitic structure. At 2000 W, the build-up zone was consisted of TiC particles precipitated in a matrix of eutectic carbides, martensite plus an inter-lamellar retained austenite. The hardness of the cladded area was remarkably improved (1330 HV in case of 700 W: 5.5 times of the hardness of substrate

  10. Dry sliding wear of Ni alloyed austempered ductile iron

    Directory of Open Access Journals (Sweden)

    E. Akbarzadeh Chiniforush

    2016-09-01

    Full Text Available Measurements of dry sliding wear are presented for ductile irons with composition Fe-3.56C-2.67Si-0.25Mo-0.5Cu and Ni contents of 0.8 and 1.5 in wt.% with applied loads of 50, 100 and 150 N for austempering temperatures of 270, 320, and 370 °C after austenitizing at 870 °C for 120 min. The mechanical property measurements show that the grades of the ASTM 897M: 1990 Standard can be satisfied for the selected austempering conditions. The results show that wear resistance is independent of austempering temperature with an applied load of 50 N, but there is a strong dependence at higher austempering temperatures with applied loads of 100 and 150 N. Observations indicate that wear is due to subsurface fatigue with cracks nucleated at deformed graphite nodules.

  11. Colour Metallography of Cast Iron - Chapter 3: Spheroidal Graphite Cast Iron (Ⅰ

    Directory of Open Access Journals (Sweden)

    Zhou Jiyang

    2010-02-01

    Full Text Available Cast iron, as a traditional metal material, has advantages of low total cost, good castability and machinability, good wear resistance and low notch sensitivity, and is still facing tough challenge in quality, property and variety of types etc. Experts and engineers studying and producing iron castings all around world extremely concern this serious challenge. Over more than 30 years, a great of research work has been carried out on how to further improve its property, expand its application and combine cast iron technology with some hi-techs (for example, computer technology. Nevertheless, cast iron is a multi-element and multi-phase alloy and has complex and variety of structures and still has great development potential in structure and property. For further studying and developing cast iron, theoretical research work is important promise, and the study on solidification process and control mechanism of graphite morphology is fundamental for improving property of cast iron and developing new type of cast iron. Metallography of cast iron normally includes two sections: liquid phase transformation and solid phase transformation. The book, Colour Metallography of Cast Iron, uses colour metallography technique to study solidification structures of cast irons: graphite, carbides, austenite and eutectics; and focuses on solidification processes. With progress of modern solidification theory, the control of material solidification process becomes important measure for improving traditional materials and developing new materials. Solidification structure not only influences mechanical and physical properties of cast iron, but also affects its internal quality. The book uses a large amount of colour photos to describe the formation of solidification structures and their relations. Crystallization phenomena, which cannot be displayed with traditional metallography, are presented and more phase transformation information is obtained from these colour

  12. Analysis and simulation of non-metallic inclusions in spheroidal graphite iron

    Science.gov (United States)

    Pustal, B.; Schelnberger, B.; Bührig-Polaczek, A.

    2016-03-01

    Non-metallic inclusions in spheroidal cast iron (SGI) reduce fatigue strength and yield strength. This type of inclusion usually accumulates at grain boundaries. Papers addressing this topic show the overall impact of both the fraction of so-called white (carbides) and black (non-metallic) inclusions on mechanical properties. In the present work we focus on the origin and the formation conditions of black Mg-bearing inclusions, further distinguishing between Si-bearing and non-Si-bearing Mg inclusions. The formation was simulated applying thermodynamic approaches. Moreover, appropriate experiments have been carried out and a large number of particles have been studied applying innovative feature analysis with regard to shape, size, and composition. Magnesium silicates are predicted at elevated oxygen concentrations, whereas at low levels of oxygen sulphides and carbides appear at a late stage of solidification. Experiments with three consecutive flow obstacles show that the amount of magnesium silicates decrease after each of the three obstacles, whereas the fraction of non-Si-bearing inclusions remains approximately constant. The size of inclusions divides in halves over the flow path and the number of particles increases accordingly. We point out that based on feature analysis Mg-O-C bearing inclusion show disadvantageous form factors for which reason this kind of inclusions may be extremely harmful in terms of crack initiation. All results obtained indicate that magnesium silicates are entrapped on mould filling, whereas Mg-(O, C, S, P, N) bearing particles are precipitates at late stages of solidification. Consequently, the only avoidance strategy is setting up optimum retained magnesium content.

  13. Improvement of static strength and fatigue crack propagation resistance in ductile cast iron by austempering from (. alpha. +. gamma. ) phase region. Bubun austenpering shori ni yoru kyujo kokuen chutetsu no seiteki kyodo to hiro kiretsu shinten teiko no kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Y.; Asami, K.; Matsuoka, S. (Musashi Institute of Technology, Tokyo (Japan))

    1991-06-15

    The spheroidal graphite cast iron is better characterized in resistivity against the abrasion and heat, and economical efficiency than the normal carbon steel. Notice being taken of treatment temperature (800 to 840 centigrade) in the ({alpha}+{gamma}) phase region for the partial austempering treatment condition, able to improve the spheroidal graphite cast iron simultaneously in both statical tensile characteristics and fatigue crack propagation resistance, the present report compared dual phase as-cast material, single phase ferrite and single phase bainite. As a result, the morphological ratio of bainite becomes about 20% to the base morphology at 800 centigrade in treatment temperature. Then with progressively heightening to 815, 830 and 840 centigrade in it, the above ratio so heightens to about 40, 80 and 90%, respectively. The fatigue crack propagation resistance in the low DeltaK (low stress intensity factor) region is heightened by the partial austempering treatment to higher than that of dual phase as-cast material, single phase ferrite and single phase bainite, and most done at 800 centigrade in temperature where the bainite becomes about 20% in morphological ratio. 830 centigrade where the bainite becomes about 80% is judged to be the most appropriate treatment temperature for both the statical tensile characteristics and fatigue crack propagation resistance. 3 refs., 16 figs., 3 tabs.

  14. Austempered Ductile Iron Machining

    Science.gov (United States)

    Pilc, Jozef; Šajgalík, Michal; Holubják, Jozef; Piešová, Marianna; Zaušková, Lucia; Babík, Ondrej; Kuždák, Viktor; Rákoci, Jozef

    2015-12-01

    This article deals with the machining of cast iron. In industrial practice, Austempered Ductile Iron began to be used relatively recently. ADI is ductile iron that has gone through austempering to get improved properties, among which we can include strength, wear resistance or noise damping. This specific material is defined also by other properties, such as high elasticity, ductility and endurance against tenigue, which are the properties, that considerably make the tooling characteristic worse.

  15. A Microscale Model for Ausferritic Transformation of Austempered Ductile Irons

    Science.gov (United States)

    Boccardo, Adrián D.; Dardati, Patricia M.; Celentano, Diego J.; Godoy, Luis A.

    2017-01-01

    This paper presents a new metallurgical model for the ausferritic transformation of ductile cast iron. The model allows predicting the evolution of phases in terms of the chemical composition, austenitization and austempering temperatures, graphite nodule count, and distribution of graphite nodule size. The ferrite evolution is predicted according to the displacive growth mechanism. A representative volume element is employed at the microscale to consider the phase distributions, the inhomogeneous austenite carbon content, and the nucleation of ferrite subunits at the graphite nodule surface and at the tips of existing ferrite subunits. The performance of the model is evaluated by comparison with experimental results. The results indicate that the increment of the ausferritic transformation rate, which is caused by increments of austempering temperature and graphite nodule count, is adequately represented by this model.

  16. Continuous cooling transformation behavior for heat treatment of spheroidal graphite cast iron. Kyujo kokuen chutetsu no netsushoriji ni okeru renzoku reikyaku hentai kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Nakata, T.; Matsumoto, H. (Shibaura Institute of Technology, Tokyo (Japan)); Kasugai, T. (National Research Institute for Metals, Tsukuba (Japan)); Koyama, M. (Automobile Foundry Co. Ltd., Yokohama (Japan))

    1992-08-25

    In order to study basic heat treatment properties of spheroidal graphite cast iron, the continuous cooling transformation(CCT) diagrams for the material equivallent to FCD700 under various austenitized conditions were obtained. There were 4 kinds of austenitized conditions varying from 1123K and 420s to 1323K and 1,800s. Eight kinds of cooling time from the austenitized temperature to 773K ranged from 6s to 4,000s. The transformation temperature was measured by a thermal expansion method. When the austenitized temperature was increased from 1123K to 1323K, ferrite and pearlite transformation regions moved a little in the CCT diagrams and the martensite transformation temperature decreased from 493K to 458K. The bainite region in the CCT diagrams disappeared at the austenite temperatures above 1223K. The nucleation sites of ferrite and pearlite in the spheroidal graphite cast iron were generated at grain boundary between austenite and graphite but not at grain boundary between austenites. The reason of such phenomena was also studied. 10 refs., 8 figs., 2 tabs.

  17. Tensile properties of austempered ductile iron under thermomechanical treatment

    Science.gov (United States)

    Achary, J.

    2000-02-01

    A new processing method was investigated for improving the strength and elongation of austempered ductile iron (ADI) by grain refinement of parent austenite using thermomechanical treatment. The material was deformed at the austenitization temperature by single and multipass rolling before the austempering treatment. The effects of the amount of deformation, austenitization temperature, austempering temperatures, reaustenitization, and secondary deformation on the tensile properties were studied. The properties obtained using the method were compared with those of the ASTM standards. The effect of deformation on the graphite shape was also studied. Tensile strength/yield strength/elongation values were found to increase with increasing austenite deformation up to 40% and then to start decreasing. Tensile strength/yield strength and elongation values of 1700 MPa/1300 MPa/5% and 1350 MPa/920 MPa/15% can be achieved with this method in the ranges of variables studied.

  18. Tensile properties of austempered ductile iron under thermomechanical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Achary, J.

    2000-02-01

    A new processing method was investigated for improving the strength and elongation of austempered ductile iron (ADI) by grain refinement of parent austenite using thermomechanical treatment. The material was deformed at the austenitization temperature by single and multipass rolling before the austempering treatment. The effects of the amount of deformation, austenitization temperature, austempering temperatures, reaustenitization, and secondary deformation on the tensile properties were studied. The properties obtained using the method were compared with those of the ASTM standards. The effect of deformation on the graphite shape was also studied. Tensile strength/yield strength/elongation values were found to increase with increasing austenite deformation up to 40% and then to start decreasing. Tensile strength/yield strength and elongation values of 1,700 MPa/1,300 MPa/5% and 1,350 MPa/920 MPa/15% can be achieved with this method in the ranges of variables studied.

  19. Reduction of industrial waste by the employment of simultaneous desulfurization/graphite spheroidization method using magnesium; Maguneshiumu wo mochiita datsuryu/kokuen kyujoka doji shoriho no saiyo ni yoru sangyo haikibutsu no teigen

    Energy Technology Data Exchange (ETDEWEB)

    Toriyama, T.; Yamamuro, S.; Yoshida, A.; Ono, S. [Kurimoto Ltd., Osaka (Japan)

    1996-10-25

    The Sakai Factory of KURIMOTO LTD. employed a continuous porous plug desulfurization method in 1992. In this desulfurization method, the molten iron from a cupola is desulfurized with a desulfurizing agent in which calcium carbide and lime are mixed. This paper reports the details of the development of a simultaneous desulfurization/graphite spheroidization method using Mg, which aims at disusing the operation in a high-temperature environment and reducing the quantity of slag which is an industrial waste. The main results obtained are as follows. The quantity of desulfurized slag in a porous plug ladle could be reduced to zero. A total quantity of slag produced was reduced by about 70%, which was better than the target reduction. Owing to the employment of this simultaneous desulfurization/graphite spheroidization method using Mg, the operations of mixing the desulfurizing agent and removing desulfurized slag in a high-temperature environment were omitted. The S-value after the simultaneous desulfurization/graphite spheroidization became lower than 0.010%. It could be ascertained that the graphite spheroidization rate and mechanical properties of the product did not differ from those of the product obtained by a conventional desulfurization and fully satisfied the standard values of the product. 8 figs., 4 tabs.

  20. Effect of austempering temperature on cavitation behaviour of unalloyed ADI material

    Energy Technology Data Exchange (ETDEWEB)

    Dojcinovic, Marina [University of Belgrade, Faculty of Technology and Metallurgy, Karnegijeva 4, Belgrade (Serbia); Eric, Olivera [Innovation Centre, Faculty of Mechanical Engineering, University of Belgrade, Kraljice Marije 16, Belgrade (Serbia); Rajnovic, Dragan; Sidjanin, Leposava [Department of Production Engineering, Faculty of Technical Sciences, University of Novi Sad, Trg Dositeja Obradovića 6, Novi Sad (Serbia); Balos, Sebastian, E-mail: sebab@uns.ac.rs [Department of Production Engineering, Faculty of Technical Sciences, University of Novi Sad, Trg Dositeja Obradovića 6, Novi Sad (Serbia)

    2013-08-15

    This paper provides an in-depth study and description of cavitation damage and microstructural changes in two types of unalloyed austempered ductile iron (ADI). ADI materials used were austempered at 300 and 400 °C having ausferrite microstructure with 16 and 31.4% of retained austenite, respectively. Metallographic examination was carried out to study the morphology of their cavitation-damaged surfaces. Cavitation damage was initiated at graphite nodules as well as in the interface between a graphite nodule and an ausferrite matrix. Furthermore, microcracking and ferrite/retained austenite morphology were proved to be of great importance for cavitation resistance. Mass loss rate revealed that ADI austempered at 400 °C has a higher cavitation resistance in water than ADI austempered at 300 °C. A higher amount of retained austenite in ADI austempered at 400 °C played an important role in increasing cavitation resistance. The good cavitation behaviour of ADI austempered at 400 °C was due to the matrix hardening by stress assisted phase transformation of retained austenite into martensite (SATRAM) phenomenon, as shown by X-ray diffraction analysis. - Highlights: • Cavitation rate of two ADI materials was tested. • ADI material with a lower hardness has had a lower cavitation rate. • The main reason is microstructural transformations during cavitation. • SATRAM phenomenon increases cavitation resistance.

  1. Microstructures and Mechanical Properties of a Wear-Resistant Alloyed Ductile Iron Austempered at Various Temperatures

    Science.gov (United States)

    Cui, Junjun; Chen, Liqing

    2015-08-01

    To further improve the mechanical performance of a new type of alloyed bainitic wear-resistant ductile iron, the effects of the various austempering temperatures have been investigated on microstructure and mechanical behaviors of alloyed ductile iron Fe-3.50C-1.95Si-3.58Ni-0.71Cu-0.92Mo-0.65Cr-0.36Mn (in weight percent). This alloyed ductile iron were firstly austenitized at 1123 K (850 °C) for 1 hour and then austempered in a salt bath at 548 K, 573 K, and 598 K (275 °C, 300 °C, and 325 °C) for 2 hours according to time-temperature-transformation diagram calculated by JMatPro software. The microstructures of austempered wear-resistant ductile irons consist of matrix of dark needle-like ferrite plus bright etching austenite and some amount of martensite and some dispersed graphite nodules. With increasing the austempering temperature, the amount of ferrite decreases in austempered ductile iron, while the amount of austenite and carbon content of austenite increases. There is a gradual decrease in hardness and increase in compressive strength with increasing austempering temperature. The increased austenite content and coarsened austenite and ferrite can lead to a hardness decrease as austempering temperature is increased. The increased compressive strength can be attributed to a decreased amount of martensitic transformation. The alloyed ductile iron behaves rather well wear resistance when the austempering is carried out at 598 K (325 °C) for 2 hours. Under the condition of wear test by dry sand/rubber wheel, the wear mechanisms of austempered ductile irons are both micro-cutting and plastic deformation.

  2. Integrated modeling and heat treatment simulation of austempered ductile iron

    Science.gov (United States)

    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.

  3. Production of austempered ductile iron gears for transmission cases

    Energy Technology Data Exchange (ETDEWEB)

    Sagin, A. [Metallurgy Engineering Dept., Technical Univ. of Yildiz, Istanbul (Turkey); Topuz, A. [Chemical and Metallurgical Faculty, Technical Univ. of Yildiz, Istanbul (Turkey)

    2005-07-01

    The investigations presented in this contribution were targeted to replace a gear group made up of SAE 8620 steel in army jeeps with microstructural controlled austempered ductile iron, in order to reduce the manufacturing steps. Furthermore, the vibrations were also expected to decrease, due to the application of austempered ductile iron. The fatigue resistance of unalloyed and Ni alloyed austempered ductile iron have been investigated to see if some improvement as compared to steels with cementite could be achieved. The effect of the austenization heat treatment on the fatigue resistance was studied in metallographic investigations and it turned out that the alloying elements Cu, Ni and Mo have a beneficial effect. For economical reasons, the gears were fabricated of nodular iron containing 3.98% C, 1.89% Si, 0.269% Mn and 0.028% P. Considering the fatigue resistance, a Ni alloyed material with 3.66% C, about 1.81% Si, 0.134% Mn, 0.031% P and 1.51% Ni was chosen. The roundness of the graphites was about 93-100% and 80-85%. The gears were at first produced by austenization at 900 C for 3 hours and then by austempering at 235 C for 2.5 hours. The fatigue tests were performed at the maximum stresses to be expected. (orig.)

  4. Fracture toughness of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, M.N. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering; Komatsu, S. [Kinki Univ., Higashihiroshima (Japan). Dept. of Mechanical Systems Engineering

    1995-12-01

    The effect of austenitizing temperature, austempering temperature and austempering time on the fracture toughness of austempered ductile iron have been presented and discussed in this paper. Statistical design of experiments with a 2{sup 3} matrix was used to determine the effect of the individual variables and their interactions. The desirable combination of the three variables is suggested based on the analysis.

  5. Influence of slit depth on impact value of ferritic nodular graphite cast iron. Feraito kyujo kokuen chutetsu no shogekichi ni oyobosu suritto fukasa no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Sunada, H. (Himegi Inst. of Technology, Hyogo (Japan). Faculty of Engineering)

    1992-10-15

    Impact experiment and fracture surface observations were carried out in order to study the effect of slit depth on the impact value during austempering of ferrite spheroidal graphite east iron. The tensile strength has been increased by austempering, however the impact value was not improved. The bending strength of slit bottom for each structure has been less influenced by slit depth, and it has been almost similar, The value obtained by the multiplication by binding coefficient has been higher than yield strength in case of ferrite structure, and it has been lower in case of bainitic structure. Cleavage facets along with the large dimples originating from graphites and small dimples from inclursions, have been observed on the impact fracture surface of ferrite structure, however in general, the fracture has been ductile. The deformation around the graphite has been small for bainitic structure, pseudo brittleness type fracture surface is formed, and has been less rough compared to ferrite structure. 9 refs., 8 figs., 1 tab.

  6. Austempering kinetics of Cu-Ni alloyed austempered Ductile Iron

    Science.gov (United States)

    Cekic, Olivera Eric; Sidjanin, Leposava; Rajnovic, Dragan; Balos, Sebastian

    2014-11-01

    The aim of the paper was to investigate the effect of austempering parameters (time and temperature) on the microstructure and mechanical properties of ADI alloyed with 1.5% Cu and 1.6% Ni (in wt.%) in order to establish the optimal processing window. It was shown that the strength, elongation and impact energy strongly depend on the amounts of ausferritic ferrite and retained austenite. A processing window was established according to the results of the kinetics of the isothermal transformation. The results show that the processing window for ADI alloyed with Cu and Ni at 350 °C was relatively wide, while the processing window for the isothermal transformation at 400 °C becomes narrower and shifted to the left. The processing window of ADI austempered at 300 °C is also narrower, but shifted to the right towards the longer times compared to the processing window of ADI austempered at 350 °C.

  7. Effect of Austempering on Plastic Behavior of Some Austempered Ductile Iron Alloys

    Science.gov (United States)

    Olofsson, Jakob; Larsson, Dan; Svensson, Ingvar L.

    2011-12-01

    A numerical description relating microstructure to elastic and plastic deformation behavior would make it possible to simulate the mechanical behavior of complex cast components with tailored material properties. Limited work and data, however, have been published regarding the connection between microstructure and plastic behavior of austempered ductile irons (ADIs). In the current work, the effects of austempering temperature and austempering time on the strength coefficient and the strain hardening exponent of the Hollomon equation were investigated for two ADI alloys. The results show that the plastic behavior is highly dependent on the combination of austempering temperature and austempering time. It was found that as the austempering temperature increases, both the strength coefficient and the strain hardening exponent initially decrease, but after reaching a minimum at the critical austempering temperature, they show a plateau or an increase. The effect of the austempering time on the plastic behavior depends on the austempering temperature. At low austempering temperatures, the strength coefficient and the strain hardening exponent decrease with increased austempering time, whereas at higher austempering temperatures, they show little time dependence. These relations are explained by the microstructural transformations that take place during the austempering heat treatment.

  8. Tensile properties of copper alloyed austempered ductile iron: Effect of austempering parameters

    Science.gov (United States)

    Batra, U.; Ray, S.; Prabhakar, S. R.

    2004-10-01

    A ductile iron containing 0.6% copper as the main alloying element was austenitized at 850 °C for 120 min and was subsequently austempered for 60 min at austempering temperatures of 270, 330, and 380 °C. The samples were also austempered at 330 °C for austempering times of 30 150 min. The structural parameters for the austempered alloy austenite (X γ ), average carbon content (C γ ), the product X γ C γ , and the size of the bainitic ferrite needle (d α ) were determined using x-ray diffraction. The effect of austempering temperature and time has been studied with respect to tensile properties such as 0.2% proof stress, ultimate tensile strength (UTS), percentage of elongation, and quality index. These properties have been correlated with the structural parameters of the austempered ductile iron microstructure. Fracture studies have been carried out on the tensile fracture surfaces of the austempered ductile iron (ADI).

  9. Wear behavior of an austempered ductile iron containing Mo-Ni-Cu

    Energy Technology Data Exchange (ETDEWEB)

    Yazdani, S.; Rahimi, M.A. [Faculty of Materials Engineering, Sahand Univ. of Technology, Tabriz (Iran)

    2005-07-01

    The aim of the this investigation is to study the influence of Ni on tribiological behavior of an austempered ductile iron (ADI) containing Mo, Ni and Cu. Ductile irons with chemical composition Fe-3.56%C-2.67%Si -0.25%Mo-0.5%Cu and Ni contents of 0.8 and 1.5% were cast into standard Y-blocks. Wear test samples were machined off from the bottom section of blocks. Austenitizing heat treatment was carried out at 870 C temperature followed by austempering at 270, 320, and 370 C for 5-1140 minutes. The wear test was carried out by using block-on-ring test machine. Sliding dry wear behavior was studied under applied loads of 50, 100 and 150 N. The results show that wear resistance is independent of austempering temperature with an applied load of 50 N, but there is a strong dependence at higher austempering temperatures with applied loads of 100 and 150 N. Wear mechanism is described as being due to subsurface fatigue, with cracks nucleated at plastically, deformed graphite interfaces. The wear controlling mechanism is the crack growth when wear shows a dependence on applied load and austempering temperature. (orig.)

  10. Influence of Copper Addition and Temperature on the Kinetics of Austempering in Ductile Iron

    Science.gov (United States)

    Amran, Yogev; Katsman, Alexander; Schaaf, Peter; Bamberger, Menachem

    2010-10-01

    Austempered ductile iron (ADI) is a material that exhibits excellent mechanical properties because of its special microstructure, combining ferrite and austenite supersaturated with carbon. Two ADI alloys, Fe-3.5 pct C-2.5 pct Si and Fe-3.6 pct C-2.7 pct Si-0.7 pct Cu, austempered for various times at 623 K (350 °C) and 673 K (400 °C) followed by water quenching, were investigated. The first ferrite needles nucleate mainly at the graphite/austenite interface. The austenite and ferrite weight fractions increase with the austempering time until stabilization is reached. The increase in the lattice parameter of the austenite during austempering corresponds to an increase of carbon content in the austenite. The increase in the ferrite weight fraction is associated with a decrease in microhardness. As the austempering temperature increases, the ferrite weight fraction decreases, the high carbon austenite weight fraction increases, but the carbon content in the latter decreases. Copper addition increases the high carbon austenite weight fraction. The results are discussed based on the phases composing the Fe-2Si-C system.

  11. Austempered ductile iron process development

    Science.gov (United States)

    Gupta, C. D.; Keough, J. R.; Pramstaller, D. M.

    1986-11-01

    Pressure from imports and material substitution has severly affected demand for domestic iron industry products. It is estimated that the potential market for Austempered Ductile Iron (ADI) is as large as the market for carburized and/or through hardened forgings. The primary interest in ADI is generated by the economics of process. Improved machinability and reduced processing costs as well as interesting physical properties has created an enormous interest in all metalworking industries towards ADI. The development of gas-fired austempering processes and resoluton of technical and economic uncertainities concerning the process will help improve the outlook for iron founderies.

  12. Neutron diffraction study of austempered ductile iron

    Science.gov (United States)

    Choi, C. S.; Sharpe, W.; Barker, J.; Fields, R. J.

    1996-04-01

    Crystallographic properties of an austempered ductile iron (ADI) were studied by using neutron diffraction. A quantitative phase analysis based on Rietveld refinements revealed three component phases, α-Fe (ferrite), γ-Fe (austenite), and graphite precipitate, with weight fractions of 66.0, 31.5, and 2.5 pct, respectively. The ferrite phases of the samples were found to be tetragonal, 14/mmm, with a c/a ratio of about 0.993, which is very close to the body-centered cubic (bcc) structure. The austenite phase had C atoms occupying the octahedral site of the face-centered cubic (fcc) unit cell with about 8 pct occupancy ratio. A strong microstrain broadening was observed for the two Fe phases of the samples. The particle sizes of the acicular ferrite phase were studied by using small angle neutron scattering. The analysis suggested a mean rod diameter of 700 A. The scattering invariant predicts a ferrite volume fraction consistent with the powder diffraction analysis. A textbook case of nodular graphite segregation, with average diameters ranging from 10 to 20 μm, was observed by optical micrography.

  13. Properties investigation of austempered ductile iron

    OpenAIRE

    Sudhanshu Detwal; Deivanathan R

    2016-01-01

    This work concerns microstructural and mechanical properties of an austempered ductile cast iron (ADI). The ductile iron material was produced by the sand mould casting technique. Afterwards, austempering heat treatment was applied to the specimens at two different temperatures of 250°C and 350°C. Austempered Ductile Irons (ADIs) were produced successfully by different two-stage heat treatments, to obtain favorable microstructure and hardness. The microstructure and hardness obtained by such ...

  14. Development of high toughness in austempered type ductile cast iron and evaluation of its properties

    Science.gov (United States)

    Kobayashi, Toshiro; Yamamoto, Hironobu

    1988-02-01

    In order to increase the toughness of austempered ductile cast irons, we attempted to strengthen the fracture initiation sites such as graphite-matrix interfaces and eutectic cell boundaries in a way of the microsegregation of alloying elements. For instance, the retained austenite which is stable under external stresses may be introduced preferentially into these sites by the addition of Ni, which segregates to a graphite periphery and of Mn, which partitions mainly to eutectic cell boundaries. Following this concept, the effects of various austempering processes on toughness are also in-vestigated. The cast iron alloying with Ni and Mn shows the best fracture toughness when it is heat-treated by either QB' or B' process; here, the QB' means the oil-quenching from an austenite γ phase range followed by austempering from a ferrite α plus γ range and the B' means austempering from a (α + γ) range. In the newly developed iron, there is a mixed microstructure composed of the ferrite, bainitic ferrite, and austenite. Abnormal elongation due to the TRIP effect in the austenite phase is found to have occurred at about 198 K. Moreover, it is shown that this TRIP effect may be caused by the formation of deformation twins.

  15. Properties investigation of austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Sudhanshu Detwal

    2016-03-01

    Full Text Available This work concerns microstructural and mechanical properties of an austempered ductile cast iron (ADI. The ductile iron material was produced by the sand mould casting technique. Afterwards, austempering heat treatment was applied to the specimens at two different temperatures of 250°C and 350°C. Austempered Ductile Irons (ADIs were produced successfully by different two-stage heat treatments, to obtain favorable microstructure and hardness. The microstructure and hardness obtained by such variable heat treatments were compared. The austempering temperature and time were found to be decisive parameters in obtaining a desired ADI microstructure.

  16. Some Mechanical Properties of Austempered Ductile Iron

    Science.gov (United States)

    Waanders, F. B.; Vorster, S. W.; Vorster, M. J.

    1998-12-01

    In the present investigation the influence of the microstructure, obtained after an austempering treatment in a "process window", on the mechanical properties of austempered ductile iron has been investigated. These properties include tensile strength, elongation and hardness. Conversion electron Mössbauer spectra (CEMS) were measured, after heat treatment.

  17. Some mechanical properties of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Waanders, F.B.; Vorster, S.W.; Vorster, M.V. [Potchefstroom Univ. (South Africa). Dept. of Metall. Eng.

    1997-12-01

    In the present investigation the influence of the microstructure, obtained after an austempering treatment in a ``process window``, on the mechanical properties of austempered ductile iron has been investigated. These properties include tensile strength, elongation and hardness. Conversion electron Moessbauer spectra (CEMS) were measured, after heat treatment. (orig.). 7 refs.

  18. Some Mechanical Properties of Austempered Ductile Iron

    Energy Technology Data Exchange (ETDEWEB)

    Waanders, F.B.; Vorster, S.W.; Vorster, M.J. [Potchefstroom University, Department of Metallurgical Engineering (South Africa)

    1998-12-15

    In the present investigation the influence of the microstructure, obtained after an austempering treatment in a 'process window', on the mechanical properties of austempered ductile iron has been investigated. These properties include tensile strength, elongation and hardness. Conversion electron Moessbauer spectra (CEMS) were measured, after heat treatment.

  19. The Nature of the Tensile Fracture in Austempered Ductile Iron with Dual Matrix Microstructure

    Science.gov (United States)

    Kilicli, Volkan; Erdogan, Mehmet

    2010-02-01

    The tensile fracture characteristics of austempered ductile irons with dual matrix structures and different ausferrite volume fractions have been studied for an unalloyed ductile cast iron containing (in wt.%) 3.50 C, 2.63 Si, 0.318 Mn, and 0.047 Mg. Specimens were intercritically austenitized (partially austenitized) in two phase region (α + γ) at various temperatures for 20 min and then quenched into a salt bath held at austempering temperature of 365 °C for various times and then air cooled to room temperature to obtain various ausferrite volume fractions. Conventionally austempered specimens with fully ausferritic matrix and unalloyed as-cast specimens having fully ferritic structures were also tested for comparison. In dual matrix structures, results showed that the volume fraction of proeutectoid ferrite, new (epitaxial) ferrite, and ausferrite [bainitic ferrite + high-carbon austenite (stabilized or transformed austenite)] can be controlled to influence the strength and ductility. Generally, microvoids nucleation is initiated at the interface between the graphite nodules and the surrounding ferritic structure and at the grain boundary junctions in the fully ferritic microstructure. Debonding of the graphite nodules from the surrounding matrix structure was evident. The continuity of the ausferritic structure along the intercellular boundaries plays an important role in determining the fracture behavior of austempered ductile iron with different ausferrite volume fractions. The different fracture mechanisms correspond to the different levels of ausferrite volume fractions. With increasing continuity of the ausferritic structure, fracture pattern changed from ductile to moderate ductile nature. On the other hand, in the conventionally austempered samples with a fully ausferritic structure, the fracture mode was a mixture of quasi-cleavage and a dimple pattern. Microvoid coalescence was the dominant form of fracture in all structures.

  20. Effect of Austempering on Plastic Behavior of Some Austempered Ductile Iron Alloys

    OpenAIRE

    Olofsson, Jakob; Larsson, Dan; Svensson, Ingvar L

    2011-01-01

    A numerical description relating microstructure to elastic and plastic deformation behavior would make it possible to simulate the mechanical behavior of complex cast components with tailored material properties. Limited work and data have however been published regarding the connection between microstructure and plastic behavior of austempered ductile irons (ADI). In the current work the effects of austempering temperature and austempering time on the strength coefficient and the strain hard...

  1. Investigation of the chip formation of austempered grey iron

    Science.gov (United States)

    Lung, S.; Klocke, F.; Döbbeler, B.; Krick, E.

    2016-10-01

    By a heat treatment process the strength and thus the field of applications of Grey Cast Iron (GI) can be increased to a range which is comparable to Compacted Graphite Iron (CGI). The microstructure of the resulting material consists of austenite and acicular ferrite. This material is named Austempered Grey Iron (AGI). Until now the material has not yet made its way to widespread use, due to the unknown machinability. For an economical use the machinability of the material must be at least at the level of CGI. This work deals with the chip formation, as an evaluation criterion for the machinability and represents a first step towards a comprehensive assessment of machining of AGI materials. To investigate the chip formation chip roots of three different AGI grades, a GI and a CGI were produced in a turning process. The chip roots were prepared to analyse the deformation of the microstructure during the chip formation.

  2. Fundamental Research on Hobbing of Austempered Ductile Iron Gear

    Science.gov (United States)

    Matsuoka, Hironori; Tsuda, Yoshihiro; Ono, Hajime

    In this study, the influence of graphite particles (number of graphite particles) in austempered ductile iron (ADI) on tool wear and finished surface roughness was investigated, using TiN and (Al, Ti)N coated high-speed steel cutting tools in hobbing. The experiments were performed using a fly tool of the same geometry as that of one blade of a hob, at the cutting speed of 47m/min in dry cutting. As a consequence, the following points were clarified: (1) ADI having an average number of 284 graphite particles per 1mm2 (the average diameter of 28.0µm) showed a good machinability without causing tool failure. The tool life was improved when using the (Al, Ti)N coated tool, and the finished surface roughness Ry was 3.5µm at the end of cutting. (2) It was suggested that the adhesion of deposited metal on the rake face influences the tool failure which occurred when cutting ADI. (3) The interrelation between the center wear and the surface roughness was recognized.

  3. Influece of the austempering temperature on the tensile strength of the austempered ductile iron (ADI samples

    Directory of Open Access Journals (Sweden)

    S. Savićević

    2017-01-01

    Full Text Available Austempered Ductile Iron (ADI is a class of ductile iron subjected to a two-step heat treatment process – austenitization and austempering. The heat treatment gives to ADI a high value of tensile strength and an especially good strength-to-weight ratio. However, designers in most cases are unfamiliar with this material that can compete favorably with steel and aluminum castings, weldments and forgings. The high tensile strength of ADI is the result of its unique ausferrite microstructure. In this paper, an investigation of the influence of the austempering temperature on the tensile strength of the ADI samples is presented.

  4. Mechanical Property Stability of Cu-Mo-Ni Alloyed Austempered Ductile Iron

    Institute of Scientific and Technical Information of China (English)

    LIU Sheng-fa; WANG Zhong-fan

    2005-01-01

    The aim of present work is to investigate the influencing factors on mechanical property stability of Cu-Mo-Ni alloyed austempered ductile iron (ADI). The results show that after austenitized at 900 ℃ for 2 h followed by austempered at 370 ℃ for another 2 h, the mechanical property of the alloyed ADI can reach the Germanite GGG-100 standard, i.e.σb≮1 000 MPa, δ≮5%, at 95% confidence level. And the satisfactory mechanical properties were obtained when the alloyed ADI was austenitized at 850 ℃ to 1 000 ℃ for 1-4 h, and austempered at 355 ℃ to 400 ℃ for another 1 h to 4 h. The microstructures, including nodule number, white bright zone content (martensite-containing interdendritic segregation zone) and retained austenite content, can significantly influence the mechanical properties of the ADI. In order to obtain the good combinations of strength and ductility, the volume fraction of white bright zone should be less than 5%, and the retained austenite contents maintain between 30 % and 40 %. The application of inoculation techniques to increase graphite nodule number can effectively reduce the white bright zone content in the structure.

  5. Thin Wall Austempered Ductile Iron (TWADI

    Directory of Open Access Journals (Sweden)

    M. Górny

    2009-07-01

    Full Text Available In this paper the analysis of thin walled castings made of ductile iron is considered. It is shown that thin wall austempered ductile iron can be obtained by means of short-term heat treatment of thin wall castings without addition of alloying elements. Metallographic examinations of 2 mm thin walled castings along with casting with thicker wall thickness (20x28 mm after different austempring conditions are presented. It has been proved that short-term heat treatment amounted 20 minutes of austenitizing at 880 oC followed by holding at 400 oC for 5 minutes causes ausferrite matrix in 2 mm wall thickness castings, while casting with thicker wall thickness remain untransformed and martensite is still present in a matrix. Finally there are shown that thin wall ductile iron is an excellent base material for austempering heat treatments. As a result high mechanical properties received in thin wall plates made of austempered ductile iron.

  6. Effects of austempering conditions on the microstructures and mechanical properties in Fe-0.9%C-2.3%Si-0.3%Mn steel

    Science.gov (United States)

    Son, Je-Young; Kim, Ji-Hun; Kim, Won-Bae; Ye, Byung-Joon

    2010-06-01

    In this study, the effect of the microstructure and mechanical properties of austempered high-carbon (0.9 %C) high-silicon (2.3 %Si) cast steel were investigated. The specimens were austenitised for 60 min. at 900 °C, and austempered at 260 °C, 320 °C, and 380 °C for periods of time ranging from 30 min to 240 min. After receiving this heat treatment, the mechanical properties were measured using both a tensile test and hardness test. To analyze the microstructure, an optical microscope was used and an X-ray diffraction (XRD) analysis was carried out. In this study, high carbon high silicon cast steel without graphite and with higher tensile strength (1300 MPa to 2200 MPa) and elongation (˜25 %), when compared to austempered ductile cast iron (ADI), was developed. When the austempering temperature was at 260 °C, the microstructures were low ausferrite, but at 380 °C, an upper ausferrite structure was formed. As the austempering temperature increased from 260 to 380 °C, the ultimate tensile strength and hardness decreased, but the elongation and retained austenite volume fraction increased. In addition, the microstructures were coarser.

  7. Influece of the austempering temperature on the tensile strength of the austempered ductile iron (ADI) samples

    OpenAIRE

    Savićević, S.; Avdušinović, H.; A. Gigović-Gekić; Z. Jurković; Vukčević, M.; M. Janjić

    2017-01-01

    Austempered Ductile Iron (ADI) is a class of ductile iron subjected to a two-step heat treatment process – austenitization and austempering. The heat treatment gives to ADI a high value of tensile strength and an especially good strength-to-weight ratio. However, designers in most cases are unfamiliar with this material that can compete favorably with steel and aluminum castings, weldments and forgings. The high tensile strength of ADI is the result of its unique ausferrite microstructure. In...

  8. Calorimetric examinations of austempered ductile iron ADI

    Directory of Open Access Journals (Sweden)

    F. Binczyk

    2007-12-01

    Full Text Available The study presents the results of calorimetric examinations during heating and cooling of austempered ductile iron ADI after austempering at temperatures of 280, 330 and 380oC. The samples for examinations were taken from cast rods of 20 and 60 mm diameter. Examinations were carried out on a differential scanning calorimeter, type Multi HTC S60. During heating, on a DSC curve one strong exothermic effect has been noted to occur (it does not occur in the case of common-grade cast iron, accompanied by two endothermic effects. The exothermic effect occurs within the range of about 20oC. Depending on the temperature of austempering treatment, its beginning falls to the temperatures from 469 to 490oC. The heat of this effect is proportional to the austenite content in ADI matrix after austempering. The endothermic effects are related with decomposition of pearlite (or bainite and with phase transformation α → γ (ferrite as a constituent of ausferritic matrix.

  9. Nondestructive Evaluation of the Austempered Ductile Cast Irons

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S. S.; Lee, S. K. [Korea Standards Research Institute, Daejeon (Korea, Republic of)

    1989-05-15

    Austempered ductile cast iron (ADI) which has been recently developed shows good mechanical properties. These properties are related to the microstructure which is greatly affected by processing variables such as austempering time and temperature. In this study, the relationships between mechanical properties from impact test, and hardness test and the results from ultrasonic velocity measurement and electrical resistivity measurement are studied on the ADI samples which are heat treated at different austempering temperature and time. From the results, we conclude the followings. The ultrasonic velocity measurement could be used for the study of austempering reaction mechanism. The electrical resistivity measurement could be used as quality assurance technique for the ADI

  10. Effects of austempering heat treatment conditions on fracture toughness of austempered ductile cast iron; Kyujo kokuen chutetsu no hakai jinsei ni oyobosu austemper shori no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Y.; Arai, M. [Musashi Institute of Technology, Tokyo (Japan)

    1996-03-25

    Discussions were given in various manners to learn effects of treatment conditions with respect to fracture toughness of austempered ductile cast iron. Austenitizing temperature and isothermal transforming conditions that result in comprehensively most excellent fracture toughness including tensile strength were 1173 K and 648 K - 3.6 ks, respectively. The austenitizing temperature as low as 1123 K reduces quantity of residual austenite, resulting in residual inclusion of free ferrite in the structure. If as high as 1223 K, reduction in the fracture toughness is caused under any condition as a result of increase in unstable austenite and growth of austenite into coarse particles. With respect to the isothermal transforming conditions, high fracture toughness may be achieved at a relatively high temperature. However, a structure that has been transformed from austenite to bainite causes a secondary reaction in a short time, and deposits particulates of cementite and graphite, leading to a prediction of decrease in the fracture toughness. Therefore, it is preferable that the treatment time is decreased in order to suppress the secondary reaction. 9 refs., 10 figs., 7 tabs.

  11. Effects of boron addition and austempering time on microstructure, hardness and tensile properties of ductile irons

    Energy Technology Data Exchange (ETDEWEB)

    Guerra L, F.V. [Instituto de Inv. En Metalurgia y Materiales UMSNH, México (Mexico); Bedolla-Jacuinde, A., E-mail: abedollj@icloud.com [Instituto de Inv. En Metalurgia y Materiales UMSNH, México (Mexico); Mejía, I. [Instituto de Inv. En Metalurgia y Materiales UMSNH, México (Mexico); Facultad de Ingeniería Mecánica UAEH, México (Mexico); Zuno, J. [Facultad de Ingeniería Mecánica UAEH, México (Mexico); Maldonado, C. [Instituto de Inv. En Metalurgia y Materiales UMSNH, México (Mexico)

    2015-11-11

    The present work analyzes the effect of boron addition to an Austempered Ductile Iron, in amounts from zero to 120 ppm. It has been found that boron has a strong effect on the equivalent carbon content, resulting in an increase on the precipitated graphite volume and a decrease in the dissolved carbon content in the matrix. This in turn, increases the ferrite volume fraction in the as-cast conditions from 0.24 in the base alloy to 0.78 for the iron with 120 ppm of boron. Furthermore, a decrease in the nodularity from 100% in the base alloy to 83% with 120 ppm of boron has been observed. During austempering, the transformation to ausferrite was faster and lower volumes of martensite and unstable austenite were detected when boron increased; this promoted lower hardness values, 239 HV for the base iron and 189 HV for the 120 ppm boron alloy. The increase in hardness and strength, typical for the start of bainite formation, were not observed in the boron added irons, but just in the base alloy. Under this basis, it is assumed that at least the addition of 60 ppm of boron extended the optimal processing window. The higher values of strength and ductility were obtained for the alloy with 60 ppm of boron; these results are discussed in terms of the graphitizing effect of boron in these irons and the reduced amount of carbon dissolved in austenite.

  12. The austempering study of alloyed ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Eric, Olivera [Institute of Nuclear Sciences ' Vinca' , P.O. Box 522, 11001 Belgrade (Serbia and Montenegro)]. E-mail: oliverae@vin.bg.ac.yu; Jovanovic, Milan [Institute of Nuclear Sciences ' Vinca' , P.O. Box 522, 11001 Belgrade (Serbia and Montenegro); Sid-baranin, Leposava [University of Novi Sad, Faculty of Technical Sciences, Novi Sad (Serbia and Montenegro); Rajnovic, Dragan [University of Novi Sad, Faculty of Technical Sciences, Novi Sad (Serbia and Montenegro); Zec, Slavica [Institute of Nuclear Sciences ' Vinca' , P.O. Box 522, 11001 Belgrade (Serbia and Montenegro)

    2006-07-01

    Austempered ductile iron (ADI) proved to be an excellent material as it possesses attractive properties: high strength, ductility and toughness are combined with good wear resistance and machinability. These properties can be achieved upon adequate heat treatment which yields optimum microstructure for a given chemical composition. In this paper an investigation has been conducted on ADI alloyed with 0.45%Cu and austempered in a range of times and temperatures. The microstructure and fracture mode developed throughout these treatments have been identified by means of light and scanning electron microscopy and X-ray diffraction analysis. It was shown that strength, elongation and impact energy strongly depend on amounts of bainitic ferrite and retained austenite. Based on these results an optimal processing window has been established.

  13. Abrasive wear behaviour of as cast and austempered ductile irons

    Energy Technology Data Exchange (ETDEWEB)

    Baydogan, M.; Koekden, M.U.; Cimenoglu, H. [Istanbul Technical Univ., Dept. of Metallurgy and Materials Science Engineering Istanbul (Turkey)

    2000-07-01

    In this study, abrasive wear behaviour of as cast and austempered GGG 50 and GGG 80 quality ductile irons was investigated. In the as cast condition, GGG 50 and GGG 80 quality ductile irons were having ferritic and pearlitic matrix structures, respectively. Austempering at 250 C after austenitisation at 900 C for 100 minutes produced bainitic matrix structure in both of the investigated ductile irons. Abrasive wear tests performed by rubbing the as cast and austempered specimens on Al{sub 2}O{sub 3} abrasive bands, revealed that austempering treatment improves abrasion resistance about 10-70% depending on the abrasive particle size and composition of the base iron. In the as cast condition, pearlitic GGG 80 grade ductile iron, has higher wear resistance than ferritic GGG 50 grade ductile iron. In the austempered condition GGG 50 and GGG 80 grade ductile irons which have bainitic matrix structure, exhibit almost similar wear resistance. (orig.)

  14. 350℃ - Thermal Stability of Austempered Ductile Iron

    Institute of Scientific and Technical Information of China (English)

    M. Pellizzari; M. Zadra, A. Molinari

    2004-01-01

    The thermal stability of an ADI has been studied by isothermal aging at 350℃ for 150 hours, measuring the amount of retained austenite and its carbon content by X-ray diffractometry. The influence of different austempering treatments, carried out at temperatures between 300 and 450℃ (300, 330, 360, 410 and 450℃) and holding times between15 and 60 minutes (15, 30, 45, 60), was considered. Thermal stability depends on whether austempering temperature is higher or lower than the ageing one. Thermal stability increases by increasing austempering temperatures, from 300° to410℃. Samples treated at 410° and 450° show a lower austenite decomposition than samples at 300-330-360℃. A drop in stability is shown by increasing the austempering temperature from 410° to 450℃. The results have been interpreted on the basis of the austenite stability out of the processing window, which in turn depends on the austempering parameters.

  15. Stacking faults in austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Hermida, J.D. [CNEA, San Martin (Argentina). Dept. de Materiales

    1996-06-01

    During last decade, Austempered Ductile Iron (ADI) has been successfully used as an acceptable replacement material for steel in many applications, due to the relatively high strength and reasonable ductility obtained. These properties are the result of the special microstructure exhibited by this material at the end of the upper bainite reaction: ferrite platelets surrounded by high carbon stabilized austenite. However, at the beginning of the austempering treatment, the existence of interdendritic low carbon austenite is revealed by its transformation to martensite when cooling the sample or during subsequent deformation. The completion of the upper bainite reaction is of decisive importance to mechanical properties because the remaining martensite reduces ductility. It was observed that the rate of the upper bainite reaction is governed by the carbon content difference between the low and high carbon austenites. The carbon content is obtained by the lattice parameter measurement, because there exists a known expression that relates both magnitudes. Several works have used X-ray diffraction to measure the lattice parameter and phase concentrations as a function of austempering time. In these works, the lattice parameters were obtained directly from the {l_brace}220{r_brace} and {l_brace}311{r_brace} peaks position. The purpose of this work is to show more precise lattice parameters measurement and, very closely related to this, the existence of stacking faults in austenite, even at times within the processing window.

  16. Effects of silicon content and austempering condition on the impact characteristics of austempered ductile cast iron. Kyojin kyujo kokuen chutetsu no jinsei ni oyobosu osutenpa shori joken to Si ryo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Aoyama, M. (Daido Inst. of Technology, Nagoya (Japan)); Kobayashi, T. (Toyohashi Univ. of Technology, Aichi (Japan)); Matsuo, K. (Kurimoto Iron Works, Ltd., Osaka (Japan))

    1990-07-25

    Austempered spherical graphite cast iron (ADI) is extensively expeted as a mechanical structural material because of high tenacity and resilience as well as fatigue strength and wear resistance. These excellent properties are attributed to the abundantly remaining austenite because the formation of carbides is restricted by the action of the silicon element. It is, therefore, important for obtaining the strong cast iron material to control the amount of the retained austenite. In this study, the impact characteristics was investigated for acquiring the basic materials concerning the influence of the temperature, time of austempering and the amount of silicon. The added amount of silicon is most suitably 2.1%. Samples without Mn and Ni showed an impact value of about 2 times of the amount added. At 400 {degree} C, however, the impact value reduced to half by the growth of coarse ferrite and bentonite. Time of austempering was 1 hour and showed a stable impact value and load of breaking. Transition temperature shifted tolow side by the increase of amount of silicon. 14 refs., 10 figs., 1 tab.

  17. Graphite Revisited

    CERN Document Server

    Draine, B T

    2016-01-01

    Laboratory measurements are used to constrain the dielectric tensor for graphite, from microwave to X-ray frequencies. The dielectric tensor is strongly anisotropic even at X-ray energies. The discrete dipole approximation is employed for accurate calculations of absorption and scattering by single-crystal graphite spheres and spheroids. For randomly-oriented single-crystal grains, the so-called 1/3 - 2/3 approximation for calculating absorption and scattering cross sections is exact in the limit a/lambda -> 0, provides better than ~10% accuracy in the optical and UV even when a/lambda is not small, but becomes increasingly inaccurate at infrared wavelengths, with errors as large as ~40% at lambda = 10 micron. For turbostratic graphite grains, the Bruggeman and Maxwell Garnett treatments yield similar cross sections in the optical and ultraviolet, but diverge in the infrared, with predicted cross sections differing by over an order of magnitude in the far-infrared. It is argued that the Maxwell Garnett estima...

  18. Effect of nodule count and austempering heat treatment on segregation behavior of alloying elements in ductile cast iron

    Directory of Open Access Journals (Sweden)

    E. Akbarzadeh Chiniforush

    2016-05-01

    Full Text Available The equilibrium partition ratio, k, has been measured for Mn, Mo, Si, Ni and Cu in a ductile iron with composition (wt.%: 3.45C, 0.25Mn, 0.25Mo, 2.45Si, 0.5Ni and 0.5Cu with different nodule counts obtained from different section sizes of 13, 25, 75 mm in the as cast, austenitized (at 870 °C for times 1, 4 and 6 hours and austempered (at 375 °C for times 1 to 1,440 min samples. Results show that Mn and Mo segregate positively at cell boundaries, but Si, Ni and Cu concentrate in an inverse manner in the vicinity of graphite nodules and there is a depletion of these elements at cell boundaries. Segregation curves for Ni and Cu are more smooth than for Si. Carbide formation has been observed at cell boundaries. Based on the results, the partition ratios for all elements decrease with increasing the nodule count. More carbide with coarser morphology has been observed in the microstructure with a lower nodule count. Austenitization for a longer time can decrease partition ratio, but cannot eliminate it entirely. Increasing the austenitization temperature has the same effect. Austenitizing parameters have no significant effect on carbides volume fraction. The kinetics of austempering is faster in higher nodule counts and subsequently better mechanical properties including higher ductility, strength and toughness have been observed for all austempering conditions studied.

  19. Development of austempered ductile iron timing gears; Austemper kyujo kokuen chutetsu timing gear no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, M.; Yamamoto, S.; Numajiri, S.; Nakajima, K. [Mitsubishi Motors Corp., Tokyo (Japan)

    1996-05-01

    To reduce vibration and noise of gears compared with ordinary steel gears for four cycle diesel engine of small commercial vehicles, austempered ductile iron (ADI) gears have been developed, which have excellent mechanical properties and vibration damping properties equivalent to steel gears. ADI is a material with tensile strength of 1,000 MPa, which is made by austempering the ductile iron to change matrix texture into tough bainite. For a new process method of ADI gears, austempering is conducted after gear cutting, and shaving is conducted, finally. Gear materials before austempering can be smoothly machined without deteriorating their machinability, to produce highly accurate gears. Fifteen percent of noise can be reduced for ADI gears during idling of engine, where 0.7 dB can be reduced in the noise level. The ADI gears provide superior pitting resistance to ordinary steel gears. They have nearly equivalent dedendum bending fatigue strength to ordinary soft nitrided steel gears. 6 refs., 12 figs., 2 tabs.

  20. Effect of austempering time on mechanical properties of a low manganese austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Putatunda, S.K.; Gadicherla, P.K.

    2000-04-01

    An investigation was carried out to examine the influence of austempering time on the resultant microstructure and the room-temperature mechanical properties of an unalloyed and low manganese ductile cast iron with initially ferritic as-cast structure. The effect of austempering time on the plane strain fracture toughness of this material was also studied. Compact tension and round cylindrical tensile specimens were prepared from unalloyed ductile cast iron with low manganese content and with a ferritic as-cast (solidified) structure. These specimens were then austempered in the upper (371 C) and lower (260 C) bainitic temperature ranges for different time periods, ranging from 30 min. to 3 h. Microstructural features such as type of bainite and the volume fraction of ferrite and austenite and its carbon content were evaluated by X-ray diffraction to examine the influence of microstructure on the mechanical properties and fracture toughness of this material. The results of the present investigation indicate that for this low manganese austempered ductile iron (ADI), upper ausferritic microstructures exhibit higher fracture toughness than lower ausferritic microstructures. Yield and tensile strength of the material was found to increase with an increase in austempering time in a lower bainitic temperature range, whereas in the upper bainitic temperature range, time has no significant effect on the mechanical properties. A retained austenite content between 30 to 35% was found to provide optimum fracture toughness. Fracture toughness was found to increase with the parameter (X{gamma}C{gamma}/d){sup 1/2}, where X{gamma} is the volume fraction of austenite, C{gamma} is the carbon content of the austenite, and d is the mean free path of dislocation motion in ferrite.

  1. Effect of austempering time on mechanical properties of a low manganese austempered ductile iron

    Science.gov (United States)

    Putatunda, Susil K.; Gadicherla, Pavan K.

    2000-04-01

    An investigation was carried out to examine the influence of austempering time on the resultant microstructure and the room-temperature mechanical properties of an unalloyed and low manganese ductile cast iron with initially ferritic as-cast structure. The effect of austempering time on the plane strain fracture toughness of this material was also studied. Compact tension and round cylindrical tensile specimens were prepared from unalloyed ductile cast iron with low manganese content and with a ferritic as-cast (solidified) structure. These specimens were then austempered in the upper (371 °C) and lower (260 °C) bainitic temperature ranges for different time periods, ranging from 30 min. to 4 h. Microstructural features such as type of bainite and the volume fraction of ferrite and austenite and its carbon content were evaluated by X-ray diffraction to examine the influence of microstructure on the mechanical properties and fracture toughness of this material. The results of the present investigation indicate that for this low manganese austempered ductile iron (ADI), upper ausferritic microstructures exhibit higher fracture toughness than lower ausferritic microstructures. Yield and tensile strength of the material was found to increase with an increase in austempering time in a lower bainitic temperature range, whereas in the upper bainitic temperature range, time has no significant effect on the mechanical properties. A retained austenite content between 30 to 35% was found to provide optimum fracture toughness. Fracture toughness was found to increase with the parameter ( XγCγ/d)1/2, where Xγ is the volume fraction of austenite, Cγ is the carbon content of the austenite, and d is the mean free path of dislocation motion in ferrite.

  2. Experimental study of the thermal stability of austempered ductile irons

    Science.gov (United States)

    Pérez, M. J.; Cisneros, M. M.; Valdés, E.; Mancha, H.; Calderón, H. A.; Campos, R. E.

    2002-10-01

    A nonisothermal annealing was applied to austempered Ni-Cu-Mo alloyed and unalloyed ductile irons to determine the thermal stability of the ausferritic structure. Differential thermal analysis (DTA) results were used to build the corresponding stability diagrams. The transformation starting temperature of the high carbon austenite was found to be strongly dependent on the austempering temperature, the heating rate, and the chemical composition of the iron. The Ni-Cu-Mo alloying elements and high austempering temperature increased the stability. The transformation of the austenite to ferrite and cementite is achieved via the precipitation of transition carbides identified as silico-carbides of triclinic structure.

  3. Interstellar Extinction by Spheroidal Dust Grains

    OpenAIRE

    Gupta, Ranjan; Mukai, Tadashi; Vaidya, D. B.; Sen, Asoke K.; Okada, Yasuhiko

    2005-01-01

    Observations of interstellar extinction and polarization indicate that the interstellar medium consists of aligned non-spherical dust grains which show variation in the interstellar extinction curve for wavelengths ranging from NIR to UV. To model the extinction and polarization, one cannot use the Mie theory which assumes the grains as solid spheres. We have used a T-matrix based method for computing the extinction efficiencies of spheroidal silicate and graphite grains of different shapes (...

  4. Bainitic transformation in austempered ductile iron with reference to untransformed austenite volume phenomenon

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadabadai, M.N. [Tehran Univ. (Iran, Islamic Republic of)

    1997-10-01

    Much interest has been focused on austempered ductile iron (ADI) because of its superior mechanical properties, which might be improved by further control of microstructure. It has so far been assumed that segregation of alloying elements in the intercellular region just delays bainitic reaction in these regions. However, the existence of bainite-free regions (UAV) even after 10,000 minutes at test temperature, e.g., 375 C, indicates something intrinsic to the mechanism of bainitic transformation. The bainitic transformation start (B{sub s}) temperature is a function of alloying elements; segregation of alloying elements can also alter the B{sub s} temperature. In other words, B{sub s} temperature in the region near graphite should be different from the intercellular region. Therefore, the intercellular region with higher concentration of alloying elements such as Mn should have a lower B{sub s} temperature, which leads to formation of UAV even after a long high-temperature austempering time (hereafter, this stable UAV will be named as the minimum UAV value). To examine this concept, theoretical and experimental procedures were employed.

  5. Effect of boron on the microstructure and mechanical properties of carbidic austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Peng Yuncheng; Jin Huijin [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300132 (China); Liu Jinhai, E-mail: pyc_wanhj@163.com [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300132 (China); Li Guolu [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300132 (China)

    2011-11-25

    Highlights: {yields} Boron are applied to carbidic austempered ductile iron (CADI). {yields} Boron microalloying CADI is a new high hardenability of wear-resistant cast iron. {yields} Addition of boron to CADI significantly improves hardenability. {yields} Effect of boron on the CADI grinding ball were investigated. {yields} Optimum property is obtained when boron content at 0.03 wt%. - Abstract: Carbidic austempered ductile iron (CADI) castings provide a unique combination of high hardness and toughness coupled with superior wear resistance properties, but their hardenability restricts their range of applications. The purpose of this study was to investigate the influence of boron on the microstructure and mechanical properties of CADI. The experimental results indicate that the CADI comprises graphite nodules, which are dispersive boron-carbides that are distributed in the form of strips, and the matrix is a typical ausferritic matrix. Microscopic amounts of boron can improve the hardenability of CADI, but higher boron content reduces the hardenability and toughness of CADI. The results are discussed in the context of the influence of boron content on the microstructure and mechanical properties of grinding balls.

  6. Mechanisms of poor machinability of austempered ductile iron; Austemper kyujo kokuen chutetsu no nansaku kiko

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, S.; Miyaji, H. [National Research Institute for Metals, Tsukuba (Japan); Nakajima, H. [Hosei University, Tokyo (Japan)

    1995-07-01

    For the purpose of high strength distempered ductile iron (ADD) has the potential to reduce the size and weight of automotive parts, however poor machinability has made it difficult to achieve broad commercial application. To clarify the mechanism of poor machinability of ADI, (1) the chips was analyzed by X-ray diffraction, (2) the cutting front was observed after instantaneously stopping using a quick stop device, (3) for the turning tool wear was measured and (4) sawability of material was compared using a saw test. The results were as follows: In the low cutting-speed range, it was fount teat strain induced transformation from retained austerity ({gamma}R) to martensite ({alpha}{prime}) occurred, and this corresponded to the poorest machinability in the saw test. In the high cutting-speed range. {gamma}R{yields}{alpha}{prime} transformation was limited to the damaged layer, because the temperature of chips exceeded Md point. The tool wear during turning of ADI was generated closer to the cutting edge, as compared with turning of steels. Observation of chip forming state showed that this phenomenon resulted from the following two factors: (a) the formation of saw-tooth like chips ant the decrease of the tool-chip contact length due to the spheroidal graphite, and (b) the increase of cutting force due to the high hardness of the bainitic phase and the damaged layer hardened by the {gamma}R{yields}{alpha}{prime} transformation. 24 refs., 9 figs., 3 tabs.

  7. Graphite Formation in Cast Iron

    Science.gov (United States)

    Stefanescu, D. M.

    1985-01-01

    In the first phase of the project it was proven that by changing the ratio between the thermal gradient and the growth rate for commercial cast iron samples solidifying in a Bridgman type furnace, it is possible to produce all types of graphite structures, from flake to spheroidal, and all types of matrices, from ferritic to white at a certain given level of cerium. KC-135 flight experiments have shown that in a low-gravity environment, no flotation occurs even in spheroidal graphite cast irons with carbon equivalent as high as 5%, while extensive graphite flotation occurred in both flake and spheroidal graphite cast irons, in high carbon samples solidified in a high gravity environment. This opens the way for production of iron-carbon composite materials, with high carbon content (e.g., 10%) in a low gravity environment. By using KC-135 flights, the influence of some basic elements on the solidification of cast iron will be studied. The mechanism of flake to spheroidal graphite transition will be studied, by using quenching experiments at both low and one gravity for different G/R ratios.

  8. Thin Wall Austempered Ductile Iron (TWADI)

    OpenAIRE

    M. Górny; E. Fraś

    2009-01-01

    In this paper the analysis of thin walled castings made of ductile iron is considered. It is shown that thin wall austempered ductile iron can be obtained by means of short-term heat treatment of thin wall castings without addition of alloying elements. Metallographic examinations of 2 mm thin walled castings along with casting with thicker wall thickness (20x28 mm) after different austempring conditions are presented. It has been proved that short-term heat treatment amounted 20 minutes of a...

  9. Effect of fully and semi austempering treatment on the fatigue properties of ductile cast iron

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Gun; Lim, Bok Kyu; Hwang, Jung Gak [Kangwon National Univ., Chuncheon (Korea, Republic of); Kim, Dong Youl [Samcheok National Univ., Samcheok (Korea, Republic of)

    2005-03-01

    Single phase bainite structure which is obtained by the conventional austempering treatment reduces the ductility of ductile cast iron. Because of the reduction of ductility it is possible to worsen the fatigue properties. Therefore, semi austempered ductile iron which is treated from {alpha}+{gamma} is prepared to investigate the static strength and fatigue properties in comparison with fully austempered ductile iron (is treated from {gamma}). In spite of semi austempered ductile iron shows the 86% increase of ductility. Also, semi austempered ductile iron shows the higher fatigue limit and lower fatigue crack growth rate as compared with fully austempered ductile iron. By the fractographical analysis, it is revealed that the ferrite obtained by semi austempering process brings about the plastic deformation (ductile striation) of crack tip and gives the prior path of crack propagation. The relatively low crack growth rate in semi austempered specimen is caused by above fractographical reasons.

  10. Successive Boronizing and Austempering for GGG-40 Grade Ductile Iron

    Institute of Scientific and Technical Information of China (English)

    Murat Baydogan; Seckin Izzet Akray

    2009-01-01

    Boronizing and austempering were successively applied to a GGG-40 grade ductile iron in order to combine the advantages of both process in a single treatment. This new procedure formed a 30 μm thick boride layer on the surface with subsurface matrix structure consisted of acicular ferrite and retained austenite. Reciprocating wear tests showed that successive boronizing and austempering exhibited considerably higher wear resistance than conventional boronizing having a subsurface matrix structure consisting of ferrite and pearlite.

  11. Neural Network Analysis of Tensile Strength of Austempered Ductile Iron

    OpenAIRE

    Z. Ławrynowicz; S. Dymski; M. Trepczyńska - Łent; T. Giętka

    2007-01-01

    The neural technique was applied to the analysis of the ultimate tensile strength and additionally the yield strength of austempered ductile iron (ADI). Austempered ductile iron is an excellent material and it possesses attractive properties as high strength, ductility and toughness. This paper begins with an introduction to neural networks and demonstrates the ability of the method to investigate new phenomena in cases where the information cannot be accessed experimentally. The model allows...

  12. Spheroidal wave functions

    CERN Document Server

    Flammer, Carson

    2005-01-01

    Intended to facilitate the use and calculation of spheroidal wave functions, this applications-oriented text features a detailed and unified account of the properties of these functions. Addressed to applied mathematicians, mathematical physicists, and mathematical engineers, it presents tables that provide a convenient means for handling wave problems in spheroidal coordinates.Topics include separation of the scalar wave equation in spheroidal coordinates, angle and radial functions, integral representations and relations, and expansions in spherical Bessel function products. Additional subje

  13. Design and control of chemical compositions for high-performance austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Gong Wenbang

    2012-05-01

    Full Text Available This paper presents the effects of chemical compositions of austempered ductile iron (ADI on casting quality, heat treatment process parameters and mechanical properties of final products. Through experiment and production practice, the impacts of carbon equivalent on ADI and its mechanical properties have been studied. Proper content ranges for carbon and silicon have been obtained to avoid ADI casting shrinkage and graphite floatation, as well as to achieve the optimal mechanical properties. According to the impact of silicon content on austenite phase transformation, the existing form of carbon in ADI has been analyzed, and also the formula and diagram showing the relationship between austenitizing temperature and carbon content in austenite have been deduced. The chemical composition range for high performance ADI and its control points have been recommended, to serve as a reference for production process.

  14. The effect of microstructure of low-alloy spheroidal cast iron on impact strength

    Directory of Open Access Journals (Sweden)

    T. Szykowny

    2010-01-01

    Full Text Available The study presents an evaluation of the effect of microstructure of low-alloy spheroidal cast iron on impact strength within the temperature range from –60 to 100°C. Analyses were conducted on one type of cast iron containing 0.51% Cu and 0.72% Ni. Cast iron was austempered or normalized. Values of KCV and static mechanical properties were determined. Structural and fractographic analyses were based on light and scanning microscopy as well as X-ray diffraction. It was found that thermal processing considerably improves impact strength in relation to cast iron after casting. At the same time static mechanical properties are enhanced.

  15. Dependence of fracture toughness of austempered ductile iron on austempering temperature

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P.P. [Karnatak Regional Engineering Coll. (India). Dept. of Metallurgical and Materials Engineering; Putatunda, S.K. [Wayne State Univ., Detroit, MI (United States)

    1998-12-01

    Ductile cast iron samples were austenitized at 927 C and subsequently austempered for 30 minutes, 1 hour, and 2 hours at 260 C, 288 C, 316 C, 343 C, 371 C, and 399 C. These were subjected to a plane strain fracture toughness test. Fracture toughness was found to initially increase with austempering temperature, reach a maximum, and then decrease with further rise in temperature. The results of the fracture toughness study and fractographic examination were correlated with microstructural features such as bainite morphology, the volume fraction of retained austenite, and its carbon content. It was found that fracture toughness was maximized when the microstructure consisted of lower bainite with about 30 vol pct retained austenite containing more than 1.8 wt pct carbon. A theoretical model was developed, which could explain the observed variation in fracture toughness with austempering temperature in terms of microstructural features such as the width of the ferrite blades and retained austenite content. A plot of K{sub IC}{sup 2} against {sigma}, (X{sub {gamma}}C{sub {gamma}}){sup 1/2} resulted in a straight line, as predicted by the model.

  16. Dependence of fracture toughness of austempered ductile iron on austempering temperature

    Science.gov (United States)

    Rao, P. Prasad; Putatunda, Susil K.

    1998-12-01

    Ductile cast iron samples were austenitized at 927 °C and subsequently austempered for 30 minutes, 1 hour, and 2 hours at 260 °C, 288 °C, 316 °C, 343 °C, 371 °C, and 399 °C. These were subjected to a plane strain fracture toughness test. Fracture toughness was found to initially increase with austempering temperature, reach a maximum, and then decrease with further rise in temperature. The results of the fracture toughness study and fractographic examination were correlated with microstructural features such as bainite morphology, the volume fraction of retained austenite, and its carbon content. It was found that fracture toughness was maximized when the microstructure consisted of lower bainite with about 30 vol pct retained austenite containing more than 1.8 wt pct carbon. A theoretical model was developed, which could explain the observed variation in fracture toughness with austempering temperature in terms of microstructural features such as the width of the ferrite blades and retained austenite content. A plot of K {/IC 2} against σ y ( X γ, C γ)1/2 resulted in a straight line, as predicted by the model.

  17. Effects of various austempering temperatures on fatigue properties in ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Salman, S. [Marmara University, Technical Education Faculty, Istanbul (Turkey); Findik, F. [Materials Technology Department, Technical Education Faculty, Sakarya University, Sakarya (Turkey)]. E-mail: findik@sakarya.edu.tr; Topuz, P. [Yildiz Technical University, Department of Metallurgy and Material, Istanbul (Turkey)

    2007-07-01

    Austempering is an isothermal heat treatment which when applied to ferrous materials, produces a structure that is stronger and tougher than comparable structures produced with conventional heat treatments. In this paper, ductile iron specimens were applied to various austempering temperatures and interpreted fatigue properties. In this test, Denison 7615 fatigue machine was used for doing double sided bending stresses. The iron was austenitized at 900 deg. C and then austempered at 235, 300 and 370 deg. C for 2 h within a salt bath to obtain various austempered microstructures. Also, the fatigue properties of the bainitic structures which occurred by austempering are examined by scanning electron microscope.

  18. Thin wall ductile and austempered iron castings

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2010-07-01

    Full Text Available It has been shown that it is possible to produce thin wall castings made of ductile iron with wall thickness in the range of 1.2 to 2.9 mm(without chills, cold laps and misruns. Thin wall ductile iron castings can be lighter (380 g than their substitutes made of aluminium alloys (580g. The kinetics of austenitising transformation was studied in unalloyed ductile iron. The advance of transformations during austenitising was monitored by measurement the fraction of martensite and also by dilatometic studies. It has been shown that in thin wall ductile iron castings austenitising at 880 oC for 20 minutes is adequate to obtain the austenite matrix at the end of the first stage of austempering heat treatment cycle.

  19. Effect of austempering temperature on microstructure and mechanical properties of unalloyed ductile iron: Vpliv austempering temperature na mikrostrukturo in mehanske lastnosti nelegirane duktilne sive litine:

    OpenAIRE

    Bošnjak, Branka; Radulović, Branko

    1999-01-01

    Austempered ductile cast iron (ADI) has emerged in the last several decades as a major engeneering material. The heat-treating of the ductile cast iron produces austempered ductile iron (ADI) with an excellent combination of strength, fracture toughness and wear resistance for a wide variety of applications in automotive, rail and heavy engineering industries. The austempering temperature is the most important parameter in determining both the structure and the mechanical properties of unallo...

  20. The role of graphite morphology and matrix structure on low frequency thermal cycling of cast irons

    Indian Academy of Sciences (India)

    S Y Buni; N Raman; S Seshan

    2004-02-01

    Low frequency thermal cycling tests were carried out on four types of cast iron (viz., austempered ductile iron, pearlitic ductile iron, compacted/vermicular graphite iron and grey cast iron) at predetermined ranges of thermal cycling temperatures. The specimens were unconstrained. Results show that austempered ductile iron has the highest thermal cycling resistance, followed by pearlitic ductile iron and compacted graphite iron, while grey cast iron exhibits the lowest resistance. Microstructural analysis of test specimens subjected to thermal cycling indicates that matrix decomposition and grain growth are responsible for the reduction in hardness while graphite oxidation, de-cohesion and grain boundary separation are responsible for the reduction in the modulus of elasticity upon thermal cycling.

  1. Voronoi-Tessellated Graphite Produced by Low-Temperature Catalytic Graphitization from Renewable Resources.

    Science.gov (United States)

    Zhao, Leyi; Zhao, Xiuyun; Burke, Luke T; Bennett, J Craig; Dunlap, Richard A; Obrovac, Mark N

    2017-09-11

    A highly crystalline graphite powder was prepared from the low temperature (800-1000 °C) graphitization of renewable hard carbon precursors using a magnesium catalyst. The resulting graphite particles are composed of Voronoi-tessellated regions comprising irregular sheets; each Voronoi-tessellated region having a small "seed" particle located near their centroid on the surface. This suggests nucleated outward growth of graphitic carbon, which has not been previously observed. Each seed particle consists of a spheroidal graphite shell on the inside of which hexagonal graphite platelets are perpendicularly affixed. This results in a unique high surface area graphite with a high degree of graphitization that is made with renewable feedstocks at temperatures far below that conventionally used for artificial graphites. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Influence of microstructure on fracture toughness of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P.P.; Putatunda, S.K. [Wayne State Univ., Detroit, MI (United States). Dept. of Chemical Engineering and Materials Science

    1997-07-01

    An investigation was carried out to examine the influence of microstructure on the plane strain fracture toughness of austempered ductile iron. Austempered ductile iron (ADI) alloyed with nickel, copper, and molybdenum was austenitized and subsequently austempered over a range of temperatures to produce different microstructures. The microstructures were characterized through optical microscopy and X-ray diffraction. Plane strain fracture toughness of all these materials was determined and was correlated with the microstructure. The results of the present investigation indicate that the lower bainitic microstructure results in higher fracture toughness than upper bainitic microstructure. Both volume fraction of retained austenite and its carbon content influence the fracture toughness. The retained austenite content of 25 vol pct was found to provide the optimum fracture toughness. It was further concluded that the carbon content of the retained austenite should be as high as possible to improve fracture toughness.

  3. Strain Induced Martensitic Transformation in Austempered Ductile Iron (ADI)

    Science.gov (United States)

    Li, X. H.; Saal, P.; Gan, W. M.; Landesberger, M.; Hoelzel, M.; Hofmann, M.

    2016-09-01

    The strain induced martensitic transformation in austempered ductile iron (ADI) has been investigated using high resolution neutron diffraction on samples compressed ex-situ to different plastic strains. In addition bulk texture measurements using neutron diffraction have been performed to calculate the orientation distribution of ferrite and austenite phases for different strain levels. Combing the detailed texture information with neutron diffraction pattern proved to be essential for quantitative phase analysis and extraction of martensite phase fractions. The martensite content induced by strain in ADI depends on austempering temperature and degree of deformation.

  4. Carbon content of austenite in austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Chang, L.C. [Kuang Wu Inst. of Tech. and Commerce, Taipei (Taiwan, Province of China). Dept. of Mechanical Engineering

    1998-06-05

    The development of austempered ductile iron (ADI) is a major achievement in cast iron technology. The austempering heat treatment enables the ductile cast iron containing mainly strong bainitic ferrite and ductile carbon-enriched austenite, with some martensite transforms from austenite during cooling down to room temperature. A key factor controlling the stability of the retained austenite can be evaluated soundly using the thermodynamics principles. It is the purpose here to demonstrate that the data of ADI from numerous sources have a similar trend.

  5. Thermomechanical treatment of austempered ductile iron

    Directory of Open Access Journals (Sweden)

    A. A. Nofal

    2007-11-01

    Full Text Available The production of lightweight ferrous castings with increased strength properties became unavoidable facing the serious challenge of lighter aluminum and magnesium castings. The relatively new ferrous casting alloy ADI offers promising strength prospects, and the thermo-mechanical treatment of ductile iron may suggest a new route for production of thin-wall products. This work aims at studying the influence of thermomechanical treatment, either by ausforming just after quenching and before the onset of austempering reaction or by cold rolling after austempering. In the first part of this work, ausforming of ADI up to 25% reduction in height during a rolling operation was found to add a mechanical processing component compared to the conventional ADI heat treatment, thus increasing the rate of ausferrite formation and leading to a much finer and more homogeneous ausferrite product. The kinetics of ausferrite formation was studied using both metallographic as well as XRD-techniques. The effect of ausforming on the strength was quite dramatic (up to 70% and 50% increase in the yield and ultimate strength respectively. A mechanism involving both a refined microstructural scale and an elevated dislocation density was suggested. Nickel is added to ADI to increase hardenability of thick section castings, while ausforming to higher degrees of deformation is necessary to alleviate the deleterious effect of alloy segregation on ductility. In the second part of this work, the influence of cold rolling (CR on the mechanical properties and structural characteristics of ADI was investigated. The variation in properties was related to the amount of retained austenite (γr and its mechanically induced ransformation. In the course of tensile deformation of ADI, transformation induced plasticity (TRIP takes place, indicated by the increase of the instantaneous value of strain-hardening exponent with tensile strain. The amount of retained austenite was found to

  6. Influence of Heat Treatment Conditions on Microstructure and Mechanical Properties of Austempered Ductile Iron After Dynamic Deformation Test

    Directory of Open Access Journals (Sweden)

    Myszka D.

    2014-10-01

    Full Text Available In this article, an attempt was made to determine the effect of dynamic load on the austempered ductile iron resistance obtained under different conditions of heat treatment. Tests were carried out on six types of cylindrical ductile iron samples austempered at 320, 370 and 400oC for 30 and 180 minutes. For each type of material, two samples were collected. As a next step in the investigations, the samples were subjected to a Taylor impact test. The samples after striking a non-deformable, rigid target were deformed on their front face. After Taylor test, a series of material tests was performed on these samples, noting a significant increase of hardness in the deformed part. This was particularly well visible in the ductile iron isothermally quenched at higher temperatures of 370 and 400oC. Inthezone of sample deformation, an increase in the content of ferromagnetic phase was also reported, thus indicating the occurrence of martensitic transformation in the microstructure containing mechanically unstable austenite. A significant amount of deformed graphite was also observed, which was a symptom of the deformation process taking place in samples. The ductile iron was characterized by high toughness and high resistance to the effect of dynamic loads, especially as regards the grade treated at a temperature of 370oC.

  7. Wear resistance properties of austempered ductile iron

    Science.gov (United States)

    Lerner, Y. S.; Kingsbury, G. R.

    1998-02-01

    A detailed review of wear resistance properties of austempered ductile iron (ADI) was undertaken to examine the potential applications of this material for wear parts, as an alternative to steels, alloyed and white irons, bronzes, and other competitive materials. Two modes of wear were studied: adhesive (frictional) dry sliding and abrasive wear. In the rotating dry sliding tests, wear behavior of the base material (a stationary block) was considered in relationship to countersurface (steel shaft) wear. In this wear mode, the wear rate of ADI was only one-fourth that of pearlitic ductile iron (DI) grade 100-70-03; the wear rates of aluminum bronze and leaded-tin bronze, respectively, were 3.7 and 3.3 times greater than that of ADI. Only quenched DI with a fully martensitic matrix slightly outperformed ADI. No significant difference was observed in the wear of steel shafts running against ADI and quenched DI. The excellent wear performance of ADI and its countersurface, combined with their relatively low friction coefficient, indicate potential for dry sliding wear applications. In the abrasive wear mode, the wear rate of ADI was comparable to that of alloyed hardened AISI 4340 steel, and approximately one-half that of hardened medium-carbon AISI 1050 steel and of white and alloyed cast irons. The excellent wear resistance of ADI may be attributed to the strain-affected transformation of high-carbon austenite to martensite that takes place in the surface layer during the wear tests.

  8. Design and optimization of stepped austempered ductile iron using characterization techniques

    Energy Technology Data Exchange (ETDEWEB)

    Hernández-Rivera, J.L., E-mail: jose.hernandez@cimav.edu.mx [Centro de Investigación en Materiales Avanzados-Laboratorio Nacional de Nanotecnología, Miguel de Cervantes 120, Z.C. 31109, Chihuahua (Mexico); Garay-Reyes, C.G.; Campos-Cambranis, R.E.; Cruz-Rivera, J.J. [Facultad de Ingeniería, Universidad Autónoma de San Luis Potosí, Sierra Leona 550, Lomas 2a. sección, Z.C. 78210, San Luis Potosí (Mexico)

    2013-09-15

    Conventional characterization techniques such as dilatometry, X-ray diffraction and metallography were used to select and optimize temperatures and times for conventional and stepped austempering. Austenitization and conventional austempering time was selected when the dilatometry graphs showed a constant expansion value. A special heat color-etching technique was applied to distinguish between the untransformed austenite and high carbon stabilized austenite which had formed during the treatments. Finally, it was found that carbide precipitation was absent during the stepped austempering in contrast to conventional austempering, on which carbide evidence was found. - Highlights: • Dilatometry helped to establish austenitization and austempering parameters. • Untransformed austenite was present even for longer processing times. • Ausferrite formed during stepped austempering caused important reinforcement effect. • Carbide precipitation was absent during stepped treatment.

  9. APPLICATION OF AUSTEMPERED DUCTILE IRON TO RAIL WHEEL SETS

    Directory of Open Access Journals (Sweden)

    Sacit DÜNDAR

    2003-03-01

    Full Text Available Austempered Ductile Iron (ADI is made up of a composite structure of acicular ferrite and carbon-enriched austenite. The transformation of austenite to martensite under certain stress levels results in a material with a hard rim and a tough internal structure. These properties makes it an alternate material for the production of railcar wheelsets.

  10. APPLICATION OF AUSTEMPERED DUCTILE IRON TO RAIL WHEEL SETS

    OpenAIRE

    Sacit DÜNDAR

    2003-01-01

    Austempered Ductile Iron (ADI) is made up of a composite structure of acicular ferrite and carbon-enriched austenite. The transformation of austenite to martensite under certain stress levels results in a material with a hard rim and a tough internal structure. These properties makes it an alternate material for the production of railcar wheelsets.

  11. The surface layer of austempered ductile iron investment castings properties

    OpenAIRE

    D. Myszka; M. Kłębczyk; Zych, A.; L. Kwiatkowski

    2009-01-01

    The article presents a unique process of carbonnitriding and nitriding the precision casting surfaces of austempered ductile iron. The results of the research are pointing that adequate process parameters allow to obtain multiple increase of wear resistance and a significant increase of corrosion resistance. Also, changes of cast microstructure and hardness are presented.

  12. Wear and scuffing of austempered ductile iron gears

    Energy Technology Data Exchange (ETDEWEB)

    Magalhaes, L. [Departamento de Engenharia Mecanica, Instituto Superior de Engenharia, Instituto Politecnico do Porto (Portugal); Seabra, J. [Porto Univ. (Portugal). Dept. Engenharia Mecanica e Gestao Industrial

    1998-03-01

    This paper enhances actual knowledge of the properties of austempered ductile iron (ADI) as a gear material. Results from scuffing tests performed with ADI gears on a FZG test rig are presented and discussed. Contact condition analysis is done using elast-hydrodynamic theory along with several experimental techniques, as surface electronic scanning microscopy, metallurgical spectroscopy and lubricant ferrographic analysis. (orig.)

  13. The surface layer of austempered ductile iron investment castings properties

    Directory of Open Access Journals (Sweden)

    D. Myszka

    2009-01-01

    Full Text Available The article presents a unique process of carbonnitriding and nitriding the precision casting surfaces of austempered ductile iron. The results of the research are pointing that adequate process parameters allow to obtain multiple increase of wear resistance and a significant increase of corrosion resistance. Also, changes of cast microstructure and hardness are presented.

  14. Fatigue properties of austempered ductile cast iron at room and elevated temperatures; Austemper kyujo kokuen chutetsu no chukoon ni okeru hiro tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Fukuyama, K.; Hasegawa, N.; Inaga, K. [Gifu University, Gifu (Japan)

    1995-06-15

    Austempered ductile cast iron (ADI) is used widely as a structural material with high strength and toughness. However, since few studies have been made on investigation of fatigue properties at medium to high temperatures, this paper describes rotating bending tests carried out in temperature range between room temperature and 400{degree}C to investigate the fatigue properties and the fatigue crack generating behavior. The following results were obtained: the fatigue limit (fatigue strength after 10{sup 7} bendings) showed a remarkable maximizing phenomenon at temperatures around 300{degree}C; micronization of the base structure caused by transformation of residual austenite was recognized above 300{degree}C, and so was rise in the hardness; heating to this temperature led to rise in the Ms point, making the transformation occur more easily; the effect of repetitive stress causes a processing induced transformation; the temperature at which the transformation and the micronization are completed declines by about 50{degree}C lower than in the non-transformed region; and the fatigue fracture at middle to high temperatures is caused more frequently by internally existing graphite and development of cracks from very small casting cavities. 31 refs., 10 figs., 7 tabs.

  15. Effect of alloying elements on austempered ductile iron (ADI) properties and its process: Review

    OpenAIRE

    Amir Sadighzadeh Benam

    2015-01-01

    Austempered ductile iron (ADI) parts have a unique combination of high strength and toughness with excellent design flexibility and low cost. These excellent properties are directly related to its microstructure called "ausferrite" that is the result of austempering heat treatment applied to ductile irons. Alloying elements increase ADI austemperability and change speeds of austempering reactions. Thus, they can affect ADI resultant microstructure and mechanical properties. In this paper, the...

  16. Enhancement of Fatigue Properties of Ductile Irons by Successive Austempering Heat Treatment

    Science.gov (United States)

    Jahangiri, M. R.; Ahmadabadi, M. Nili; Farhangi, H.

    2011-12-01

    The aim of this study is to evaluate the effects of austempering heat treatment on the microstructure, mechanical properties, and bending fatigue behavior of an alloyed ductile iron with chemical composition of 1.6 wt.% Ni, 0.47 wt.% manganese and 0.6 wt.% copper. Based on the results of tensile and impact tests, as well as metallographic studies, optimum heat-treating cycles were determined and applied on the standard fatigue specimens. The results showed that the fatigue strength of specimens austempered successively was practically comparable to those austempered at high temperatures and considerably greater than those austempered at low temperatures.

  17. Effect of alloying elements on austempered ductile iron (ADI properties and its process: Review

    Directory of Open Access Journals (Sweden)

    Amir Sadighzadeh Benam

    2015-01-01

    Full Text Available Austempered ductile iron (ADI parts have a unique combination of high strength and toughness with excellent design flexibility and low cost. These excellent properties are directly related to its microstructure called "ausferrite" that is the result of austempering heat treatment applied to ductile irons. Alloying elements increase ADI austemperability and change speeds of austempering reactions. Thus, they can affect ADI resultant microstructure and mechanical properties. In this paper, the effects of alloying elements on ADI mechanical properties, microstructural changes, two-stage austempering reactions, processing windows, austemperability, and other aspects are reviewed.

  18. A study of several factors governing the fatigue limits of austempered ductile cast iron with various microstructures

    Science.gov (United States)

    Kim, Jinhak; Kim, Sangtae; Kim, Mingun

    2000-06-01

    The effects the leading factors bearing on fatigue limits were investigated with three kinds of ductile iron specimens various microstructures. As a result of examination, the fatigue limits in relationship to hardness and tensile strength, the expected higher improvement for fatigue limits in the case of the high strength specimens that experienced austempering treatment are not observed in comparison with the specimens treated with stress relief treatment. The estimated maximum defect size is one of the important parameters in predicting and evaluating fatigue limits for three different heat-treated ductile cast irons. Also, a quantitative relationship can be established between the fatigue limit and maximum defect size. Moreover, it is possible to explain the difference in fatigue limits in the three ductile cast irons by application of the rates of non-propagating crack which connects the adjacent graphite nodules before it stops.

  19. Thermomechanical treatment of austempered ductile iron

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The production of lightweight ferrous castings with increased strength properties became unavoidable hter aluminum and magnesium castings. The relatively new ferrous casting alloy ADI offers promising strength prospects, and the thermo-mechanical treatment of ductile iron may suggest a new fluence of thermomechanical treatment,either by ausforming just after quenching and before the onset of austempering reaction or by cold rolling after of this work, ausforming of ADI up to 25% reduction in height during a rolling operation was found to add a mechanical processing component compared to the conventional ADI heat treatment, thus increasing the rate ics of ausferrite formation was studied using both metallographic as well as XRD-techniques. The effect of ausforming on strength was quite dramatic (up to 70% and 50% increase in the yield and ultimate strength respectively). A mechanism involving both a refined microstructural scale and an elevated dislocation density was suggested. Nickel eformation is necessary to alleviate the deleterious effect of alloy segregation on ductility.luence of cold rolling (CR) on the mechanical properties and structural characteristics ofADI wasinvestigated. The variation in properties was related to the amount of retained austenite nsformation. In the course of tensile deformation of ADI, transformation induced plasticity (TRIP) takes place, indicated by the increase of the instantaneous value of strain-hardening exponent with o partial transformation of γr to martensite under the CR strain. Such strain-induced transformation resulted in higher amounts of mechanically generated therefore increased, while ductility and impact toughness decreased with increasing CR reduction.

  20. Corrosion behavior of austempered ductile iron (ADI) in iron ore slurry

    African Journals Online (AJOL)

    grinding balls with different austempering treatments in iron ore slurry using weight ... A set of 200 balls of forged EN31 steel and austempered ductile iron were ... CuCl2 solution to prevent it from surface oxidation during the heat treatment.

  1. An austempering study of ductile iron alloyed with copper

    Directory of Open Access Journals (Sweden)

    OLIVERA ERIC

    2005-07-01

    Full Text Available Austempered ductile iron (ADI has proved to be an excellent material as it possesses attractive properties: high strength, ductility and toughness are combined with good wear resistance and machinability. These properties can be achieved upon adequate heat treatment which yields the optimum microstructure for a given chemical composition. In this paper the results of an investigation the austempering of ADI alloyed with 0.45 % Cu for a range of times and temperatures are reported. The microstructure and fracture mode developed throughout these treatments have been identified by means of light and scanning electron microscopy and X-ray diffraction analysis. It was shown that the strength, elongation and impact energy strongly depend on the amounts of bainitic ferrite and retained austenite. Based on these results, and optimal processing window was established.

  2. Bending Fatigue Strength of Austempered Ductile Iron Spur Gears

    Science.gov (United States)

    Yamanaka, Masashi; Tamura, Ryo; Inoue, Katsumi; Narita, Yukihito

    This paper deals with an experimental evaluation of bending fatigue strength for austempered ductile iron (ADI) spur gears. The module is 2.5 and the number of teeth is 26 in the test gears. The material of the test gears corresponds to Japan Industrial Standard (JIS) FCAD1100-15. Some gears are processed by one of two types of fine particle bombarding (FPB). The surface roughness is slightly increased by FPB. The obtained strengths are 623 MPa for the as-austempered gears, and 1011 and 1085 MPa for the gears after FPB. The strength is expressed by the fillet stress level, which is calculated by FEM. The strength of a gear with the same dimensions made of carburized SCr420H alloy steel is 1205 MPa, and the strength of the ADI gear is approximately half that of the carburized steel gear. The FPB process has a significant effect on the ADI gear, improving its strength by 62-74%.

  3. Austempering of hot rolled transformation-induced plasticity steels

    Institute of Scientific and Technical Information of China (English)

    Zhuang Li; Di Wu

    2008-01-01

    Thermomechanical controlled processing (TMCP) was conducted by using a laboratory hot rolling mill. Austempering inAustempering in the salt bath after hot rolling Was investigated. The effect of isothermal holding time on mechanical properties was studied throughing of the microstructure and mechanical properties of the specimens. The mechanism of transformation-induced plasticity (TRIP) was discussed. The results show that the microstructure of these steels consists of polygonal ferrite, granular bainite, and ad TRIP occur in the hot rolled Si-Mn TRIP steels. Excellent mechanical properties were obtained for various durations at 400℃. Prolonged holdingprecipitation, which destabilized the austenite. The mechanical properties were optimal when the specimen was held for 25 min, and the tensile strength, total elongation, and strength ductility balance reached the maximum values of 776 MPa, 33%,respevtively.

  4. Superior austempered ductile iron (ADI) properties achieved by prior hot isostatic pressing (HIP)

    Energy Technology Data Exchange (ETDEWEB)

    LaGoy, J.L.; Widmer, R.; Zick, D.H. [Industrial Materials Technology Inc., Andover, MA (United States)

    1996-12-31

    Ductile iron obtained from different foundries and cast by dissimilar methods has been successfully hot isostatically pressed (HIPed) before austempering to achieve substantially higher ductilities, without significant detriment to other properties, than those reached by austempering along. HIP was attempted to solve different mechanical deficiencies in austempered ductile iron (ADI) such as the lack of ductility in higher strength grades, inconsistent mechanical properties, and service life limitations. A variety of HIP temperatures were analyzed from near the austenitizing region up to within 56 C (100 F) of the melting point of ductile iron. Microporosity was eliminated by HIP at all temperatures, and subsequent austempering revealed a uniform ADI microstructure. HIP proved successful with both unencapsulated castings and those enclosed within steel canisters. Additional benefits caused by HIP processing of ductile iron castings without the austempering treatment include a significant decrease in mechanical property data scatter, high hardness at reasonable ductility levels, and a substantially reduced scrap rate.

  5. Kinetic Study of the Austempering Reactions in Ductile Irons

    Science.gov (United States)

    Pérez, M. J.; Cisneros, M. M.; Almanza, E.; Haro, S.

    2012-11-01

    Kinetics of the reaction that occur during the austempering heat treatment in unalloyed and alloyed ductile irons with 1Cu-0.25Mo, 1Ni-0.25Mo, and 0.7Cu-1Ni-0.25Mo, was studied. The austenitization and austempering cycles were achieved by isothermal dilatometry in cylindrical samples of 2 mm in diameter and 12 mm in length. The specimens were austenitized at 870 °C for 120 min, followed by isothermal holding for 300 min at temperatures between 270 and 420 °C. Kinetic parameters such as the order of reaction " n" and the rate of reaction " k" were calculated using the Johnson-Mehl equation while the empirical activation energy was calculated by means of the Arrhenius equation. It was found that the values of " k" decreased with the addition of Cu, Ni, and Mo as well as with the reduction of the isothermal temperature. The activation energy changes with the austempering temperature, in the range 30,348-58,250 J/mol when the heat treatment was carried out between 370 and 420 °C and 10,336-26,683 J/mol when the temperature varied from 270 to 350 °C. The microstructures in samples austempered at 370 and 315 °C were observed by transmission electron microscopy. No carbides precipitation was observed on samples heat treated at 370 °C for less than 120 min, while at 315 °C carbides of hexagonal structure ɛ(Fe2.4C) were found from the beginning of the transformation. The smallest value of activation energy and a slower kinetic transformation seem to be related with the presence of a carbide phase. Additionally, the time results obtained for transformation fractions of 0.05 and 0.95 by the dilatometry analysis were used to build the temperature-time-transformation diagrams for the irons.

  6. Probabilistic assessment of machine parts from Kymenite, austempered ductile iron

    Science.gov (United States)

    Petrova, I.; Galperin, M.; Alimov, M.; Jokipii, K.

    1992-07-01

    The fatigue properties of Kymenite, austempered ductile iron, were investigated on the basis of the statistical theory of fatigue failure similarity. The fatigue tests were carried out on plain and notched specimens. The S-N curves for a given failure probability and the dependencies of similarity equation parameters on the number of cycles were obtained. These data allow to take into consideration the influence of design factors in the fatigue strength.

  7. FATIGUE PROPERTIES OF AUSTEMPERED DUCTILE IRON (ADI)IN WATER ENVIRONMENT

    Institute of Scientific and Technical Information of China (English)

    Q.Z.Cai; B.K.Wei; Y.Tanaka

    2004-01-01

    The acicular ferrite in austempered ductile iron(ADI)matrix around graphite was corroded preferentially in wet condition,promoting crack origination and propagation and resulting in the disappearance of ADI fatigue limit.ADI fatigue strength was gradually reduced with increasing the time of test and was reduced by 50% in wet condition at 107 cycles compared with the fatigue limit in dry condition.The fatigue strength variation of ferritic ductile iron in wet condition was similar to that of ADI.The ferritic ductile iron,however,has better corrosion resistance so that the fatigue strength was lowered only by 10% in wet condition at 107 cycles compared with the fatigue limit in dry condition.On the other hand,the fatigue limits of A DI and ferritic ductile iron were dropped by 32% and 25% in tap water dipping 480h/dry condition respectively compared with those in dry condition.The reduction of fatigue limit was attributed to corrosion pits formation correlated with stress concentration,resulting in origination and propagation of fatigue crack.

  8. Characterization of microstructural morphology of austempered ductile iron by electron microscopy.

    Science.gov (United States)

    Guo, X L; Su, H Q; Wu, B Y; Liu, Z G

    1998-02-15

    Mechanical properties of austempered ductile iron (ADI) are mainly controlled by its unique microstructure. The objectives of this paper are to characterize the microstructural morphology and the phase distribution of ADI using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and to determine the mechanism of strengthening and toughening of ADI. The experimental results show that, in the microstructure of ADI composing of upper bainite, retained austenite, graphitic nodule, and a small amount of martensite, the upper bainite is composed of sub-units of ferrite in the shape of "wheat ears" on which the "wheat grains" grow at an angle of about 60 degrees to the long axis of the "wheat ears." The retained austenite is connected with each other in the shape of a continuous net. The wheat-ear like bainite with a homogeneous distribution in the continuous austenite net plays an important role to the strengthening and toughening of ADI. The metastable austenite appears in the shape of a large plate in which the martensite is preferentially formed. The appearance of martensite can be suppressed at the time when retained austenite remains stable, which is of benefit to the continuity and homogeneity of austenite net.

  9. The influence of chromium on mechanical properties of austempered ductile cast iron

    Science.gov (United States)

    Bartosiewicz, L.; Singh, I.; Alberts, F. A.; Krause, A. R.; Putatunda, S. K.

    1995-02-01

    An investigation was carried out to examine the influence of microstructure and chromium on the tensile properties and plane strain fracture toughness of austempered ductile cast iron (ADI). The investigation also examined the growth kinetics of ferrite in these alloys. Compact tension and round cylindrical tensile specimens were prepared from ductile cast iron with Cr as well as without Cr. These specimens were then given four different heat treatments to produce four different microstructures. Tensile tests and fracture toughness tests were carried out as per ASTM standards E-8 and E-399. The crack growth mechanism during fracture toughness tests was also determined. The test results indicate that yield strength, tensile strength, and fracture toughness of ADI increases with an increase in the volume fractions of ferrite, and the fracture toughness reaches a peak when the volume fractions of the ferrite are approximately 60% in these alloys. The Cr addition was found to reduce the fracture toughness of ADI at lower hardness levels (<40 HRC); at higher hardness levels (≥40 HRC), the effect of chromium on the fracture toughness was negligible. The crack growth mechanism was found to be a combination of quasi-cleavage and microvoid coalescences, and the crack trajectories connect the graphite nodules along the way.

  10. Prolate spheroidal quantum cloak

    Energy Technology Data Exchange (ETDEWEB)

    Syue, Cheng-De; Lin, De-Hone, E-mail: dhlin@mail.nsysu.edu.tw [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

    2015-04-15

    To understand the propagation behavior of an oblique incident matter wave in a three-dimensional non-spherical quantum cloak, we perform the transformation design for the prolate spheroidal coordinate system and obtain a quantum cloak with an ellipsoidal shape. The mass parameters and effective potential for the creation of a perfect prolate spheroidal invisibility region are given. The analytic representations of the cloaked matter wave and probability current in the cloaking shell are presented. Special attention is paid to the discussions of the probability current in the cloaking shell for only that current can manifestly exhibit how the wave vector of the matter wave is curved, rotated, and guided in the cloaking shell to flow around the non-spherically invisible region. With the current analysis, one shows that the presented cloak can perfectly guide the matter wave in the situation of any oblique incidence. The proposed prolate spheroidal cloak for matter waves provides the first non-spherically three-dimensional setup for quantum cloaking.

  11. Neural Network Analysis of Tensile Strength of Austempered Ductile Iron

    Directory of Open Access Journals (Sweden)

    Z. Ławrynowicz

    2007-07-01

    Full Text Available The neural technique was applied to the analysis of the ultimate tensile strength and additionally the yield strength of austempered ductile iron (ADI. Austempered ductile iron is an excellent material and it possesses attractive properties as high strength, ductility and toughness. This paper begins with an introduction to neural networks and demonstrates the ability of the method to investigate new phenomena in cases where the information cannot be accessed experimentally. The model allows the strength properties to be estimated as a function of heat treatment parameters and the chemical composition. A ‘committee’ model was used to increase the accuracy of the predictions. The model was validated by comparison its predictions with data of tensile tests experiments on austempered samples of ductile cast iron. The model successfully reproduces experimentally determined ultimate tensile strength and it can be exploited in the predictions of both ultimate and yield strength and in the design of chemical composition of cast irons and their heat treatments.

  12. Mechanical properties and structure of austempered ductile iron -ADI

    Directory of Open Access Journals (Sweden)

    Krzyńska A.

    2007-01-01

    Full Text Available The results of experimental study of austempered ductile iron are presented. The aim of the investigations was to look closer into the structure – mechanical properties relationships of this very attractive cast material. The experiment was carried out with 500 7 grade ductile iron, which was austempered using different parameters of heat treatment. The specimens were first solution treated 1 hour in 910oC and then isothermally quenched for different time in silicon oil bath of temperature 275, 325, 300 and 350oC. The mechanical properties heat treated specimens were tested in tensile to evaluate yield stress Re, 0.2, tensile strength Rm and elongation A10. Additionally hardness of heat treated samples was measured using Brinell-Rockwell hardness tester. Structure of the specimens was studied either with conventional metallography, scanning (SEM and transmission (TEM electron microscopy. It followed from the study that conventional grade ductile iron enabled to produce both low and high strength ADI, depend on heat treatment parameters. As expected the low temperature isothermal quenching produced higher strength ADI compare to the same ductile iron but austempered at 350oC. It was discovered however, that low yield strength ADI obtained for short time quenching at 275oC exhibited high strengthening effect while strained in tensile. So it was concluded that this had to by cause by large amount of untransformed austenite, which FCC lattice is characterized by high strengthening coefficient.

  13. Neutron Diffraction Studies of Intercritically Austempered Ductile Irons

    Energy Technology Data Exchange (ETDEWEB)

    Druschitz, Alan [University of Alabama, Birmingham; Aristizabal, Ricardo [University of Alabama, Birmingham; Druschitz, Edward [University of Alabama, Birmingham; Hubbard, Camden R [ORNL; Watkins, Thomas R [ORNL

    2011-01-01

    Neutron diffraction is a powerful tool that can be used to identify the phases present and to measure the spacing of the atomic planes in a material. Thus, the residual stresses can be determined within a component and/or the phases present. New intercritically austempered irons rely on the unique properties of the austenite phase present in their microstructures. If these materials are to see widespread use, methods to verify the quality (behavior consistency) of these materials and to provide guidance for further optimization will be needed. Neutron diffraction studies were performed at the second generation neutron residual stress facility (NRSF2) at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory on a variety of intercritically austempered irons. For similar materials, such as TRIP steels, the strengthening mechanism involves the transformation of metastable austenite to martensite during deformation. For the intercritically austempered ductile irons two different deformation/strengthening mechanisms, phase transformation and slip, dependent upon the iron chemistry, were observed. Lattice strain and phase fraction data as a function of applied stress are presented.

  14. Wear Performance of Cu-Alloyed Austempered Ductile Iron

    Science.gov (United States)

    Batra, Uma; Batra, Nimish; Sharma, J. D.

    2013-04-01

    An investigation was carried out to examine the influence of structural and mechanical properties on wear behavior of austempered ductile iron (ADI). Ductile iron (DI) samples were austenitized at 900 °C for 60 min and subsequently austempered for 60 min at three temperatures: 270, 330, and 380 °C. Microstructures of the as-cast DI and ADIs were characterized using optical and scanning microscopy, respectively. The structural parameters, volume fraction of austenite, carbon content of austenite, and ferrite particle size were determined using x-ray diffraction technique. Mechanical properties including Vicker's hardness, 0.2% proof strength, ultimate tensile strength, ductility, and strain hardening coefficient were determined. Wear tests were carried out under dry sliding conditions using pin-on-disk machine with a linear speed of 2.4 m/s. Normal load and sliding distance were 45 N and 1.7 × 104 m, respectively. ADI developed at higher austempering temperature has large amounts of austenite, which contribute toward improvement in the wear resistance through stress-induced martensitic transformation, and strain hardening of austenite. Wear rate was found to depend on 0.2% proof strength, ductility, austenite content, and its carbon content. Study of worn surfaces and nature of wear debris revealed that the fine ausferrite structure in ADIs undergoes oxidational wear, but the coarse ausferrite structure undergoes adhesion, delamination, and mild abrasion too.

  15. Fatigue behaviour of cast iron with globular graphite

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, P.; Pusch, G.; Krodel, L. [Institut fuer Werkstofftechnik, TU Bergakademie Freiberg, Gustav-Zeuner-Strasse 5, 09599 Freiberg (Germany)

    2004-07-01

    Cast iron with bainitic matrix and globular graphite, so called austempered ductile iron (ADI), allows the substitution of heat-treatable steels. The use of ADI in safety-relevant components requires knowledge of the fracture and fatigue behaviour. Cyclic stress strain behaviour and fatigue life at total strain control and random loading have been investigated at ADI (EN-GJS-1000-5) and pearlitic cast iron (EN-GJS-600-3). In addition fracture mechanic tests at cyclic loading at various stress ratios were carried out. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  16. Austempering transformation kinetics of austempered ductile iron obtained by Mössbauer Spectroscopy

    Directory of Open Access Journals (Sweden)

    F. Binczyk

    2008-10-01

    Full Text Available The composition of metallic matrix in ductile iron as-cast and after austempering at temperatures of 280, 330 and 380oC (ADI wasexamined. The study presents the results of these examinations obtained by Mössbauer spectroscopy. The specimens were taken from castrods of 60mm diameter. Using calculated values of the parameters of hyperfine interactions (isomeric shift IS, quadrupole splitting QS andhyperfine effective magnetic field H, isolated by deconvolution of the experimental spectrum, the constituents of the metallic matrix were identified in terms of both quantity and quality. The measured values as well as the data compiled in literature indicate that component Z1 (the, so called, Zeeman spectrum sextet is related with 57Fe atoms present in the structure of ferrite α1 (I stage of o→α1 + st transformation, component Z2 is typical of ferrite α2 (II stage of st→α2 + carbides transformation, while component Z3 has its origin in 57Fe atoms seated in the structure of carbides (Fe3C, Fe2C or Fe2,4C. On the other hand, by analysis of the parameters of hyperfine interactions describing the non-magnetic components (L and Q it has been proved that they are typical of austenite.

  17. Mechanical properties of a low alloyed austempered ductile iron in the upper ausferrite region

    Energy Technology Data Exchange (ETDEWEB)

    Wen, D.C.

    1999-05-01

    Microstructural observations, X-ray diffraction testing and measurements of mechanical properties were used to study the characteristics of austempering and the influence of tempered martensite on mechanical properties as a function of austempering time at 400 degree C after austenitising at 900 degree C for a 0.77%Cu-0.5%Ni ductile iron. The austempering times were derived from a resistivity curve measured by a vacuum heat treatment system. The experimental results show that the resistivity change curve could be used effectively for selecting the isothermal holding times of austempering treatment, with all The mechanical properties of ADI austempering at times corresponding to the processing window defined by the electrical resistance measurement satisfying the standard requirement. The formation of martensite in austempering reduced the mechanical properties of ADI but these properties could be increased by a treatment tempering at 200 degree C after cooling and to obtain more ductility and toughness as compared with that undergoing single heat treatment. This increase also extended the effective austempering time interval of ADI over which the ASTM standards were satisfied. (author)

  18. Microstructural and mechanical characteristics of low alloyed Ni-Mo-Cu austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Bosnjak, B.

    2000-12-01

    The present study investigated the effect of austempering temperature and austempering time on the microstructure and mechanical properties of low alloyed Ni-Mo-Cu ductile iron. The effect of austempering parameters and alloying additions on the austemperability of treated ductile iron has been estimated, too. Specimens were austenitised at 900 degree C for 120 mm, then austempered for 10, 30, 60, 120, 240 and 360 mm at 300, 350 and 400 degree C respectively, and examined by light and scanning electron microscopy. The structure consisted of bainitic ferrite containing retained austenite. the amount of which increased, and the carbon content of which decreased, with increasing austempering temperature. The carbon content of austenite has been evaluated by measuring the lattice parameter by X-ray diffraction. After short periods of austempering time in iron, the carbon content of the retained austenite decreases and on subsequent cooling to room temperature it transforms to martensite. The volume fractions of retained austenite, bainitic ferrite, martensite and austenite carbon content was correlated with microstructural changes and mechanical properties. Optimum properties are obtained at intermediate austempering periods (120-240 mm) when both the amount of retained austenite and austenite carbon content are maximum. (author)

  19. Microstructure and mechanical properties of CuNiMo austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Erić Olivera

    2004-01-01

    Full Text Available Microstructure and mechanical properties of Cu, Ni and Mo alloyed cast ductile iron have been investigated after austempering. Samples were austenitised at 860oC for 1h and then austempered at 320oC and 400oC in the interval from 0,5 to 5h. The X-ray diffraction technique and the light microscopy were utilized to investigate the bainitic transformation, while tensile and impact tests were performed for characterization of mechanical properties. By austempering at 320oC in the range between 2 and 5h, a microstructure typical for austempered ductile iron was produced, i.e. a mixture of free bainitic ferrite and highly carbon enriched retained austenite. The characteristic of the whole range of austempering at 400oC is the appearance of martensitic structure. The maximum impact energy (133 J coincides with the maximum value of volume fraction of retained austenite that was obtained after 2,5h of austempering at 320oC. The appearance of martensite during austempering at 400oC is the main cause for much lower tensile properties than at 320oC.

  20. Investigations on the fracture toughness of austempered ductile irons austenitized at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P. Prasad; Putatunda, Susil K

    2003-05-25

    Ductile cast iron was austenitized at four different temperatures and subsequently austempered at six different temperatures. Plane strain fracture toughness was evaluated under all the heat treatment conditions and correlated with the microstructural features such as the austenite content and the carbon content of the austenite. Fracture mechanism was studied by scanning electron microscopy. It was found that the optimum austempering temperature for maximum fracture toughness decreased with increasing austenitizing temperature. This could be interpreted in terms of the microstructural features. A study of the fracture mechanism revealed that good fracture toughness is unlikely to be obtained when austempering temperature is less than half of the austenitizing temperature on the absolute scale.

  1. Microstructure and mechanical properties of CuNiMo austempered ductile iron

    OpenAIRE

    Erić Olivera; Jovanović Marina P.; Šiđanin Leposava P.; Rajnović Dragan M.

    2004-01-01

    Microstructure and mechanical properties of Cu, Ni and Mo alloyed cast ductile iron have been investigated after austempering. Samples were austenitised at 860oC for 1h and then austempered at 320oC and 400oC in the interval from 0,5 to 5h. The X-ray diffraction technique and the light microscopy were utilized to investigate the bainitic transformation, while tensile and impact tests were performed for characterization of mechanical properties. By austempering at 320oC in the range between 2 ...

  2. Spheroidal Wave Functions in Electromagnetic Theory

    Science.gov (United States)

    Li, Le-Wei; Kang, Xiao-Kang; Leong, Mook-Seng

    2001-11-01

    The flagship monograph addressing the spheroidal wave function and its pertinence to computational electromagnetics Spheroidal Wave Functions in Electromagnetic Theory presents in detail the theory of spheroidal wave functions, its applications to the analysis of electromagnetic fields in various spheroidal structures, and provides comprehensive programming codes for those computations. The topics covered in this monograph include: Spheroidal coordinates and wave functions Dyadic Green's functions in spheroidal systems EM scattering by a conducting spheroid EM scattering by a coated dielectric spheroid Spheroid antennas SAR distributions in a spheroidal head model The programming codes and their applications are provided online and are written in Mathematica 3.0 or 4.0. Readers can also develop their own codes according to the theory or routine described in the book to find subsequent solutions of complicated structures. Spheroidal Wave Functions in Electromagnetic Theory is a fundamental reference for scientists, engineers, and graduate students practicing modern computational electromagnetics or applied physics.

  3. Dwarf Spheroidals in MOND

    CERN Document Server

    Angus, Garry W

    2008-01-01

    We take the line of sight velocity dispersions as functions of radius for 8 Milky Way dwarf spheroidal galaxies and use Jeans analysis to calculate the mass-to-light ratios (M/L) in Modified Newtonian Dynamics (MOND). Using the latest structural parameters, distances and variable velocity anisotropy, we find 6/8 dwarfs have sensible M/L using only the stellar populations. Sextans and Draco, however, have M/L=9.2_{-3.0}^{+5.3} and 43.9_{-19.3}^{+29.0} respectively, which poses a problem. Apart from the need for Sextans' integrated magnitude to be reviewed, we propose tidal effects intrinsic to MOND, testable with numerical simulations, but fully orbit dependant, which are disrupting Draco. The creation of the Magellanic Stream is also re-addressed in MOND, the scenario being the stream is ram pressure stripped from the SMC as it crosses the LMC.

  4. Effect of austempering parameters on microstructure and mechanical properties of horizontal continuous casting ductile iron dense bars

    OpenAIRE

    Chun-jie Xu; Pan Dai; Zheng-yang Zhang

    2015-01-01

    In the present research, the orthogonal experiment was carried out to investigate the influence of different austempering process parameters (i.e. austenitizing temperature and time, and austempering temperature and time) on microstructure and mechanical properties of LZQT500-7 ductile iron dense bars with 172 mm in diameter which were produced by horizontal continuous casting (HCC). The results show that the major factors influencing the hardness of austempered ductile iron (ADI) are austeni...

  5. Effect of shot peening process on fatigue behavior of an alloyed austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Amir Sadighzadeh Benam

    2011-08-01

    Full Text Available Shot peening is one of the most common surface treatments to improve the fatigue behavior of metallic parts. In this study the effect of shot peening process on the fatigue behavior of an alloyed austempered ductile iron (ADI has been studied. Austempering heat treatment consisted of austenitizing at 875℃ for 90 min followed by austempering at three different temperatures of 320, 365 and 400℃. Rotating-bending fatigue test was carried out on samples after shot peening by 0.4 – 0.6 mm shots. XRD and SEM analysis, micro hardness and roughness tests were carried out to study the fatigue behavior of the samples. Results indicate that the fatigue strengths of samples austempered at 320, 365 and 400℃ are increased by 27.3%, 33.3% and 48.4%, respectively, after shot peening process.

  6. Unnotched Charpy Impact Energy Transition Behavior of Austempered Engineering Grade Ductile Iron Castings

    Science.gov (United States)

    Kisakurek, Sukru Ergin; Ozel, Ahmet

    2014-04-01

    Unnotched Charpy impact energy transition behavior of five different engineering grade ductile iron castings, as specified by EN 1563 Standards, were examined in as-cast, as well as in austempered states. ADIs were produced with the maximum impact energy values permissible for the grades. Austempering treatment detrimented the sub-zero impact properties of the ferritic castings, but considerably enhanced those of the pearlitic-ferritic irons. The impact energy transition behavior of the austempered states of all the grades examined were noted to be determined by the progressive transformation of the unavoidable carbon-unsaturated and untransformed regions of the austenite remaining in the matrix of the austempered ductile iron to martensite with decreasing temperature.

  7. Influence of a novel two-step austempering process on the strain-hardening behavior of austempered ductile cast iron (ADI)

    Energy Technology Data Exchange (ETDEWEB)

    Yang Jianghuai; Putatunda, Susil K

    2004-09-25

    An investigation was carried out to examine the influence of a novel two-step austempering process on the strain-hardening behavior of austempered ductile cast iron (ADI). Strain-hardening exponent (n value) of specimens austempered by conventional single-step austempering process as well as the novel two-step process were determined over the entire plastic deformation regions of the stress-strain curves. Optical microscopy and X-ray diffraction analysis were performed to examine mechanisms of strain-hardening behavior in ADI under monotonic (tensile) loading. Test results show that this novel two-step process has resulted in improved microstructural variables in the ADI matrix, and higher hardness, yield strength and tensile strengths, but lower ductility and strain-hardening exponent values compared to the conventional single-step austempering process. Test results also indicate that strain-hardening exponent of ADI is a function of amount and morphology of microstructural constituents and interaction intensities between carbon atoms and dislocations in the matrix.

  8. CHOSEN FACTORS INFLUENCING MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AUSTEMPERED DUCTILE IRON

    Directory of Open Access Journals (Sweden)

    Alan Vaško

    2009-10-01

    Full Text Available The paper deals with some factors influencing microstructure and mechanical properties of austempered ductile iron (ADI. Final structure and properties of ADI are obtained by exactly controlled process of heat treatment of nodular cast iron. The influence of conditions of isothermal heat treatment on microstructure and mechanical properties of austempered ductile iron, especially different temperature of isothermal transformation of austenite and different holding time at this temperature, is shown in the paper.

  9. New Possibilities of Shaping the Surface Properties in Austempered Ductile Iron Castings

    OpenAIRE

    D. Myszka

    2013-01-01

    The paper presents recent developments concerning the formation of surface layer in austempered ductile iron castings. It was found thatthe traditional methods used to change the properties of the surface layer, i.e. the effect of protective atmosphere during austenitising or shot peening, are not fully satisfactory to meet the demands of commercial applications. Therefore, new ways to shape the surface layer and the surface properties of austempered ductile iron castings are searched for, to...

  10. CHOSEN FACTORS INFLUENCING MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AUSTEMPERED DUCTILE IRON

    OpenAIRE

    Alan Vaško

    2009-01-01

    The paper deals with some factors influencing microstructure and mechanical properties of austempered ductile iron (ADI). Final structure and properties of ADI are obtained by exactly controlled process of heat treatment of nodular cast iron. The influence of conditions of isothermal heat treatment on microstructure and mechanical properties of austempered ductile iron, especially different temperature of isothermal transformation of austenite and different holding time at this temperature, i...

  11. GRAPHITE EXTRUSIONS

    Science.gov (United States)

    Benziger, T.M.

    1959-01-20

    A new lubricant for graphite extrusion is described. In the past, graphite extrusion mixtures have bcen composed of coke or carbon black, together with a carbonaceous binder such as coal tar pitch, and a lubricant such as petrolatum or a colloidal suspension of graphite in glycerin or oil. Sinee sueh a lubricant is not soluble in, or compatible with the biiider liquid, such mixtures were difficult to extrude, and thc formed pieees lacked strength. This patent teaches tbe use of fatty acids as graphite extrusion lubricants and definite improvemcnts are realized thereby since the fatty acids are soluble in the binder liquid.

  12. Effects of carbides on fatigue characteristics of austempered ductile iron

    Science.gov (United States)

    Stokes, B.; Gao, N.; Reed, P. A. S.; Lee, K. K.

    2005-04-01

    Crack initiation and growth behavior of an austempered ductile iron (ADI) austenitized at 800 °C and austempered at 260 °C have been assessed under three-point bend fatigue conditions. Initiation sites have been identified as carbides remaining from the as-cast ductile iron due to insufficient austenization. The number of carbides cracking on loading to stresses greater than 275 MPa is critical in determining the failure mechanism. In general, high carbide area fractions promote coalescence-dominated fatigue crack failure, while low area fractions promote propagation-dominated fatigue crack failure. Individual carbides have been characterized using finite body tessellation (FBT) and adaptive numerical modeling (Support vector Parsimonious Analysis Of Variance (SUPANOVA)) techniques in an attempt to quantify the factors promoting carbide fracture. This indicated that large or long and thin carbides on the whole appear to be susceptible to fracture, and carbides that are locally clustered and aligned perpendicular to the tensile axis are particularly susceptible to fracture.

  13. Fatigue crack propagation characteristics of ductile cast iron austempered from (. alpha. +. gamma. ) phase region. (. alpha. +. gamma. ) iki kara austemper shorishita kyujo kokuen chutetsu no hiro kiretsu shinten tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Y.; Asami, K.; Kuroiwa, H. (Musashi Institute of Technoloyg, Tokyo (Japan))

    1991-01-15

    In order to enhance the fatigue crack propagation resistance of ductile cast iron, the effect of austempering from a ({alpha} + {gamma}) phase region was studied. As the dual phase matrix microstructure of ferrite and pearlite in as-casted iron was changed into the dual phase one of ferrite and bainite by partial austempering from 800 {degree} C, the fatigue crack propagation resistance was enhanced over the whole range of a {Delta} K region. The enhancement of the fatigue crack propagation resistance was caused by remarkable development of crack closures from higher {Delta} K regions which was induced by fracture contact and fretting because of an increase in fracture roughness and easy formation of oxide deposits. In addition, the static tensile and ductility of ductile cast iron were possibly enhanced simultaneously by partial austempering for changing pearlite into bainite superior in both tensile and ductility. 9 refs., 13 figs., 3 tabs.

  14. In Situ Study of the Influence of Nickel on the Phase Transformation Kinetics in Austempered Ductile Iron

    Science.gov (United States)

    Saal, Patrick; Meier, Leopold; Li, Xiaohu; Hofmann, Michael; Hoelzel, Markus; Wagner, Julia N.; Volk, Wolfram

    2016-02-01

    Phase fractions and austenite carbon contents in austempered ductile iron samples with three different nickel contents were determined by in situ neutron diffraction. The samples were austenitized at 1178 K (905 °C) for 30 minutes and austempered for 3.5 hours at temperatures between 523 K and 723 K (250 °C and 450 °C) using a mirror furnace. Based on the in situ neutron diffraction studies, plateau times were derived, which determine the end of stage I reaction. The austenite contents increase for higher austempering temperatures when the austempering times are selected properly, considering the accelerated phase transformation at higher temperature. Appropriate austempering times were derived for austempering temperatures between 523 K and 723 K (250 °C and 450 °C). Increased nickel contents lead to higher austenite phase fractions. Moreover the retarding effect of nickel on the phase transformation was quantified. The plateau values of phase fraction and the according austempering times were converted to TTT diagrams. The evolution of the austenite carbon content shows a maximum at 623 K (350 °C) austempering temperature. This can be explained by temperature-dependent carbide precipitation and carbon diffusion into lattice defects. Fine carbides within the ferrite could be found by preliminary APT analysis.

  15. PARAMETER OPTIMIZATION OF CARBIDIC AUSTEMPERED DUCTILE IRON USING TAGUCHI METHOD

    Directory of Open Access Journals (Sweden)

    P.DHANAPAL

    2010-08-01

    Full Text Available Carbidic austempered ductile iron [CADI] is the family of ductile iron containing wear resistance alloy carbides in the ausferrite matrix. This CADI is manufactured by selecting proper material composition through the melting route.In an effort to obtain the optimal production parameters, Taguchi method is applied. To analyse the effect of production parameters on the machanical properties, signal-to-noise (S/N ratio is calculated based on the design ofexperiments and the linear graph. The analysis of varience is calculated to find the amount of contribution of factors on individual mechanical properties and its significancy. The analytical results of taguchi method are compared with the experimental values, and it shows both are identical.

  16. Kinetics of the Bainite Transformation in Austempered Ductile Iron ADI

    Directory of Open Access Journals (Sweden)

    Ławrynowicz Z.

    2016-06-01

    Full Text Available The aim of the present research is to check an analytical model of the kinetics of bainite transformation that will enable the producers of ADI to optimise the microstructure and mechanical properties and minimise the expensive and extensive experimental trials. A combination of thermodynamics and kinetic theory was used successfully to estimate the evolution of bainite as a function of temperature, time, chemical composition and austenite grain size and predict the processing window in austempered ductile iron using a bainite transformation model developed previously for high silicon steels. The results of the present research show that the bainitic model developed for high silicon steels is applicable for calculations of the processing window for ADI.

  17. FATIGUE CRACK PROPAGATION THROUGH AUSTEMPERED DUCTILE IRON MICROSTRUCTURE

    Directory of Open Access Journals (Sweden)

    Lukáš Bubenko

    2010-10-01

    Full Text Available Austempered ductile iron (ADI has a wide range of application, particularly for castings used in automotive and earth moving machinery industries. These components are usually subjected to variable dynamic loading that may promote initiation and propagation of fatigue cracks up to final fracture. Thus, it is important to determine the fatigue crack propagation behavior of ADI. Since fatigue crack growth rate (da/dN vs. stress intensity factor K data describe fatigue crack propagation resistance and fatigue durability of structural materials, da/dN vs. Ka curves of ADI 1050 are reported here. The threshold amplitude of stress intensity factor Kath is also determined. Finally, the influence of stress intensity factor amplitude to the character of fatigue crack propagation through the ADI microstructure is described.

  18. Effects of subzero treatment on toughness of austempered ductile cast iron; Austemper kyujo kokuen chutetsu no jinsei ni oyobosu subzero shori no koka

    Energy Technology Data Exchange (ETDEWEB)

    Tsukahara, S.; Yamada, S. [Kanto Gakuin University, Yokohama (Japan)

    1998-04-25

    Specimens of austempered ductile cast iron (ADI) after constant temperature transformation at different temperatures are tested for tension, shock, and bending, and the effects of the testing methods and testing speeds on ADI strength and toughness are investigated. Specimens are made of an austempered Fe-Si-Mg alloy cast into 25mm-thick Y-shape blocks. Heat treatment is performed in the atmosphere for test pieces manufactured by machining. In the subzero treatment, the austempered pieces are cooled in water and then immediately placed in liquid nitrogen for rapid cooling. Findings obtained are mentioned below. A test piece austempered at 773K and then cooled in water retains 26% of austenite, and this disappears after a tension test. In a test piece given subzero treatment following the cooling in water, the residual austenite is found reduced from 20% to 13%. No change is observed in the amount of residual austenite before and after a bend test and impact test whether or not the test piece has been subjected to subzero treatment. 8 refs., 8 figs., 2 tabs.

  19. Effect of Copper and Nickel on the Transformation Kinetics of Austempered Ductile Iron

    Science.gov (United States)

    Górny, Marcin; Tyrała, Edward; Lopez, Hugo

    2014-10-01

    The kinetics of reaction occurring during the austempering treatment of ductile iron (DI) containing different additions of Cu and Ni was investigated in this work. DI bars were heat treated in an instrumented dilatometer in order to follow the exhibited transformation kinetics. The dilatometric results indicated that the addition of Cu alone did not have a significant effect on the incubation times for the austempering transformation. Also, the addition of both, Cu and Ni resulted in a significant effect on reducing the transformation rates. It was found that the austempering process is characterized by two clearly distinguished transformation stages. In the initial stage, the addition of Cu, and to a greater extent, additions of both Cu and Ni led to reductions in the transformation rates shifting the maximum transformation rate values toward longer times. The outcome of this work indicates that during the first stage of austempering, nucleation of the ferrite plates occurs via a diffusionless mechanism while their growth is diffusion controlled. Moreover, after the maximum in the transformation rate has been reached, the growth of ferrite plates becomes dominant with the rate-limiting step becoming the diffusion of C into the surrounding austenite. A qualitative model for the austempering transformation is proposed in this work to account for the experimental observations.

  20. In-situ measurement of phase transformation kinetics in austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Leopold, E-mail: leopold.meier@utg.de [Technische Universität München, Lehrstuhl für Umformtechnik und Gießereiwesen, Walther-Meißner-Straße 4, 85748 Garching (Germany); Hofmann, Michael, E-mail: michael.hofmann@frm2.tum.de [Technische Universität München, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Lichtenbergstraße 1, 85748 Garching (Germany); Saal, Patrick, E-mail: patrick.saal@utg.de [Technische Universität München, Lehrstuhl für Umformtechnik und Gießereiwesen, Walther-Meißner-Straße 4, 85748 Garching (Germany); Volk, Wolfram, E-mail: wolfram.volk@utg.de [Technische Universität München, Lehrstuhl für Umformtechnik und Gießereiwesen, Walther-Meißner-Straße 4, 85748 Garching (Germany); Hoffmann, Hartmut, E-mail: hartmut.hoffmann@utg.de [Technische Universität München, Lehrstuhl für Umformtechnik und Gießereiwesen, Walther-Meißner-Straße 4, 85748 Garching (Germany)

    2013-11-15

    Austempered ductile iron (ADI) alloyed with 0.42% Mn and 0.72% Cu was heat treated in a mirror furnace and the phase transitions were studied in-situ by neutron diffraction. The heat treatment consisted of austenitisation at 920 °C and isothermal austempering at 400 °C, 350 °C and 300 °C, respectively. Due to the growth of ferrite platelets, the austenite content decreases rapidly at all temperatures within the first 15–20 min and reaches a stable plateau after 35 min (400 °C) to 80 min (300 °C). The carbon content of the residual austenite, which was monitored and characterised by the change of the lattice parameter, increases up to 1.6 wt.% caused by redistribution from the newly formed ferrite. While at higher austempering temperatures this takes place almost parallel to the phase transformation, at 300 °C the redistribution of carbon to austenite lags behind considerably. Furthermore the neutron data revealed an austenite peak asymmetry during austempering which is attributed to successive phase transformation. It results temporarily in two fractions of austenite, an initial low-carbon and an enriched high-carbon modification. - Highlights: • The heat treatment of ADI was studied in detail by in-situ neutron diffraction. • The phase fractions were monitored and evaluated quantitatively. • The austenite carbon content increased up to 1.6 wt.% during austempering. • Peak asymmetries indicate two austenite fractions during highest transformation rates.

  1. Evolution of Microstructures During Austempering of Ductile Irons Alloyed with Manganese and Copper

    Science.gov (United States)

    Dasgupta, Ranjan Kumar; Mondal, Dipak Kumar; Chakrabarti, Ajit Kumar

    2013-03-01

    The influences of relatively high manganese (0.45 through 1.0 wt pct) and copper (0.56 through 1.13 wt pct) contents on microstructure development and phase transformation in three austempered ductile irons have been studied. The experimental ductile irons alloyed with copper and manganese are found to be practically free from intercellular manganese segregation. This suggests that the positive segregation of manganese is largely neutralized by the negative segregation of copper when these alloying elements are added in appropriate proportions. The drop in unreacted austenite volume (UAV) with increasing austempering temperature and time is quite significant in irons alloyed with copper and manganese. The ausferrite morphology also undergoes a transition from lenticular to feathery appearance of increasing coarseness with the increasing austempering temperature and time. SEM micrographs of the austempered samples from the base alloy containing manganese only, as well as copper plus manganese-alloyed irons, clearly reveal the presence of some martensite along with retained austenite and ferrite. X-ray diffraction analysis also confirms the presence of these phases. SEM examination further reveals the presence of twinned martensite in the copper plus manganese-alloyed samples. The possibility of strain-induced transformation of austenite to martensite during austempering heat treatment is suggested.

  2. Microstructure and mechanical properties of a new type of austempered boron alloyed high silicon cast steel

    Directory of Open Access Journals (Sweden)

    Chen Xiang

    2013-05-01

    Full Text Available In the present paper, a new type of austempered boron alloyed high silicon cast steel has been developed, and its microstructures and mechanical properties at different temperatures were investigated. The experimental results indicate that the boron alloyed high silicon cast steel comprises a dendritic matrix and interdendritic eutectic borides in as-cast condition. The dendritic matrix is made up of pearlite, ferrite, and the interdendritic eutectic boride is with a chemical formula of M2B (M represents Fe, Cr, Mn or Mo which is much like that of carbide in high chromium white cast iron. Pure ausferrite structure that consists of bainitic ferrite and retained austenite can be obtained in the matrix by austempering treatment to the cast steel. No carbides precipitate in the ausferrite structure and the morphology of borides remains almost unchanged after austempering treatments. Secondary boride particles precipitate during the course of austenitizing. The hardness and tensile strength of the austempered cast steel decrease with the increase of the austempering temperature, from 250 篊 to 400 篊. The impact toughness is 4-11 J昪m-2 at room temperature and the impact fracture fractogragh indicates that the fracture is caused by the brittle fracture of the borides.

  3. Investigation of austenitizing temperature on wear behavior of austempered gray iron (AGI)

    Science.gov (United States)

    Sarkar, T.; Sutradhara, G.

    2016-09-01

    This study is about finding the effect of austenitizing temperature on microstructure and wear behavior of copper alloyed austempered gray iron (AGI), and then comparing it with an as- cast (solidified) state. Tensile and wear tests specimens are prepared from as-cast gray iron material, and austenitized at different temperatures and then austempered at a fixed austempering temperature. Resulting microstructures are characterized through optical microscopy, scanning electron microscope (SEM) and X-Ray diffraction. Wear test is carried out using a block-on-roller multi-tribotester with sliding speed of 1.86 m/sec. In this investigation, wear behavior of all these austempered materials are determined and co-related with the micro structure. Hence the wear surface under scanning electron microscope showed that wear occurred mainly due to adhesion and delamination under dry sliding condition. The test results indicate that the austenitizing temperature has remarkable effect on resultant micro structure and wear behavior of austempered materials. Wear behavior is also found to be dependent on the hardness, tensile strength, austenite content and carbon content in austenite. It is shown that coarse ausferrite micro structure exhibited higher wear depth than fine ausferrite microstructure.

  4. SIZE AND SHAPE FACTOR EXTREMES OF SPHEROIDS

    Directory of Open Access Journals (Sweden)

    Daniel Hlubinka

    2011-05-01

    Full Text Available In the paper we consider random prolate (oblate spheroids and their random profiles. The limiting distribution of the extremal characteristics of the spheroids is related to the limiting distribution of the corresponding extremal characteristics of the profiles. The difference between the analysis of the prolate and oblate spheroids is discussed. We propose the possible application of the theoretical results.

  5. Manganese in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    North, P.; Cescutti, G.; Jablonka, P.; Hill, V.; Shetrone, M.; Letarte, B.; Lemasle, B.; Venn, K. A.; Battaglia, G.; Tolstoy, E.; Irwin, M. J.; Primas, F.; Francois, P.

    We provide manganese abundances (corrected for the effect of the hyperfine structure) for a large number of stars in the dwarf spheroidal galaxies Sculptor and Fornax, and for a smaller number in the Carina and Sextans dSph galaxies. Abundances had already been determined for a number of other

  6. The Fundamental Manifold of Spheroids

    CERN Document Server

    Zaritsky, D; Zabludoff, A I; Zaritsky, Dennis; Gonzalez, Anthony H.; Zabludoff, Ann I.

    2006-01-01

    We present a unifying empirical description of the structural and kinematic properties of all spheroids embedded in dark matter halos. We find that the stellar spheroidal components of galaxy clusters, which we call cluster spheroids (CSphs) and which are typically one hundred times the size of normal elliptical galaxies, lie on a "fundamental plane" as tight as that defined by ellipticals (rms in effective radius of ~0.07), but that has a different slope. The slope, as measured by the coefficient of the log(sigma) term, declines significantly and systematically between the fundamental planes of ellipticals, brightest cluster galaxies (BCGs), and CSphs.We attribute this decline primarily to a continuous change in M_e/L_e, the mass-to-light ratio within the effective radius r_e, with spheroid scale. The magnitude of the slope change requires that it arises principally from differences in the relative distributions of luminous and dark matter, rather than from stellar population differences such as in age and m...

  7. Investigations on the fracture toughness of austempered ductile iron alloyed with chromium

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P. Prasad; Putatunda, Susil K

    2003-04-15

    An investigation was carried out to examine the influence of chromium content on the plane strain fracture toughness of austempered ductile iron (ADI). ADIs containing 0, 0.3 and 0.5 wt.% chromium were austempered over a range of temperatures to produce different microstructures. The microstructures were characterized by optical microscopy and X-ray diffraction. Plane strain fracture toughness of all these materials was determined and correlated with microstructure and chromium content. The chromium content was found to influence the fracture toughness through its influence on the processing window. Since the chromium addition shifts the processing window to shorter durations, the higher chromium alloys at higher austempering temperatures tend to fall outside of the processing window, resulting in less than optimum microstructure and inferior fracture toughness. A small chromium addition of 0.3 wt.% was found to be beneficial for the fracture toughness of ADI.

  8. Effects of Holding Temperature for Austempering on Mechanical Properties of Si-Mn TRIP Steel

    Institute of Scientific and Technical Information of China (English)

    LI Zhuang; WU Di

    2004-01-01

    A new type of high strength steel containing a significant amount of stable retained austenite was obtained by austempering immediately after intercritical annealing. This sort of low carbon steel only contains alloying elements of silicon and manganese rather than nickel and chromium. Its mechanical properties were enhanced considerably due to strain-induced martensite transformation and transformation-induced plasticity (TRIP) of retained austenite when it was strained at temperatures between Ms and Md, because retained austenite was moderately stabilized due to carbon enrichment by austempering. Austempering was carried out at different temperatures and 400 ℃ was found to be optimal. Tensile strength, total elongation and strength-ductility balance reached the maximum values and the product of tensile strength and total elongation exceeded 30 135 MPa % when the TRIP steel was held at 400 ℃ and strained at 350 ℃.

  9. Morphology change of retained austenite during austempering of carbide-free bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Hofer, Christina, E-mail: christina.hofer@unileoben.ac.at [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Winkelhofer, Florian [Research and Development - Business Unit Coil, voestalpine Stahl GmbH, voestalpine‐Straße 3, A-4020 Linz (Austria); Clemens, Helmut; Primig, Sophie [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria)

    2016-05-10

    A change in the mechanical properties of a carbide-free bainitic steel was observed during prolonged holding at austempering temperature after termination of the bainitic transformation. To determine the origin of the property change, the microstructure was investigated by correlative electron microscopy. Although the retained austenite content remains the same during prolonged holding, its morphology changes from thin films separating the individual bainitic sub-units to a more globular structure. Since films of austenite contain a higher C concentration, the blocky austenite becomes gradually enriched in C during this morphology change. The more homogeneous distribution of the C after prolonged austempering leads to higher deformability as a result of a more pronounced TRIP effect. - Highlights: • Higher deformability after prolonged austempering of carbide-free bainite. • Microstructure-property relationship revealed by correlative electron microscopy. • Change in austenite morphology. • Spherodization of film austenite; C enrichment & homogenization of blocky austenite.

  10. The Comparison of Selected Methods of Cast Iron Spheroidization in Industrial Conditions

    Directory of Open Access Journals (Sweden)

    T. Válek

    2012-04-01

    Full Text Available Production of spheroidal graphite cast iron is today quite mastered technology. There are many methods achieving the nodular graphite morphology. Each of these methods have specific characteristics and requirements to technical support, properties and the type of applied modifier. Selection of the spheroidization method is dependent on foundry disposition, production character, economic balance, quality requirements, etc. In case of centrifugally casting the core, which fills body and neck of the roll, is created by ductile iron. Considering the sophisticated production of centrifugally cast rolls for hot rolling mills it is necessary to ensure a high reproducibility and reliability of ductile cast iron production quality in the bulk range of 9-18 t per tapping. These conditions are in the Roll Foundry in Vítkovicke Slevarny, spol. s r.o. provided and verified mastered overpour method and the newly injection of cored wire in the melt.

  11. 等温处理工艺对等温淬火球铁显微组织和硬度的影响%Effect of Austempering Technics on Microstructure and Hardness of Austempered Ductile Iron

    Institute of Scientific and Technical Information of China (English)

    亚斌; 张宝昌; 贾非; 李乃朴; 房灿峰; 郝海; 张兴国; 刘恒乐; 蔡勇; 孟宪军

    2012-01-01

    Austempered ductile iron (ADI) with high-strength and high toughness was created by method of austempering in the 1970s, which is characterized to have a tensile strength over 1000MPa, and an elongation more than 15%. With an orthogonal test and the method of austempering, the effect of the austempering technics on the microstructure and hardness of austempered ductile iron was discussed. It is found that austempered ductile iron which microstructure contains bainite and retained austenite can be gained in all of the designed austempering technics through the experiment. The hardness of samples could be mostly affected by the temperature of austempered, followed by the austenitizing temperature and austenitizing time, and the timing of austempering is proved to have the least influence on the hardness of samples.%上世纪70年代,通过奥氏体等温淬火开发出抗拉强度大于1000MPa、伸长率大于15%的高强度、高韧性等温淬火球铁。利用正交试验法,研究了等温淬火工艺参数对等温淬火球铁显微组织及硬度的影响。结果发现,在设计的试验工艺内全部可以得到以针状铁素体和富碳奥氏体为基体的等温淬火球铁组织;在等温淬火工艺中,等温淬火温度对试样硬度影响最为显著,其次是奥氏体化温度与奥氏体化时间,而等温淬火时间对于试样硬度的影响最小。

  12. Effect of austempering parameters on microstructure and mechanical properties of horizontal continuous casting ductile iron dense bars

    Directory of Open Access Journals (Sweden)

    Chun-jie Xu

    2015-03-01

    Full Text Available In the present research, the orthogonal experiment was carried out to investigate the influence of different austempering process parameters (i.e. austenitizing temperature and time, and austempering temperature and time on microstructure and mechanical properties of LZQT500-7 ductile iron dense bars with 172 mm in diameter which were produced by horizontal continuous casting (HCC. The results show that the major factors influencing the hardness of austempered ductile iron (ADI are austenitizing temperature and austempering temperature. The fraction of retained austenite increases as the austenitizing and austempering temperatures increase. When austenitizing temperature is low, acicular ferrite and retained austenite can be efficiently obtained by appropriately extending the austenitizing time. The proper austmepering time could ensure enough stability of retained austenite and prevent high carbon austenite decomposition. The optimal mechanical properties of ADI can be achieved with the following process parameters: austenitizing temperature and time are 866 °C and 135 min, and austempering temperature and time are 279 °C and 135 min, respectively. The microstructure of ADI under the optimal austempering process consists of fine acicular ferrite and a small amount of retained austenite, and the hardness, tensile strength, yield strength, elongation and impact toughness of the bars are HBW 476, 1670 MPa, 1428 MPa, 2.93% and 25.7 J, respectively.

  13. New Possibilities of Shaping the Surface Properties in Austempered Ductile Iron Castings

    Directory of Open Access Journals (Sweden)

    D. Myszka

    2013-01-01

    Full Text Available The paper presents recent developments concerning the formation of surface layer in austempered ductile iron castings. It was found thatthe traditional methods used to change the properties of the surface layer, i.e. the effect of protective atmosphere during austenitising or shot peening, are not fully satisfactory to meet the demands of commercial applications. Therefore, new ways to shape the surface layer and the surface properties of austempered ductile iron castings are searched for, to mention only detonation spraying, carbonitriding, CVD methods, etc.

  14. Influence of Hot Deformation and Subsequent Austempering on the Mechanical Properties of Hot Rolled Multiphase Steel

    Institute of Scientific and Technical Information of China (English)

    Zhuang LI; Di WU

    2006-01-01

    Influence of hot deformation and subsequent austempering on the mechanical properties of hot rolled multiphase steel was investigated. Thermo-mechanical control processing (TMCP) was conducted by using a laboratory hot rolling mill, where three different kinds of finishing rolling reduction, and austemperings with various isothermal holding duration were applied. The results have shown that a multiphase microstructure consisting of polygonal ferrite, granular bainite and larger amount of stabilized retained austenite can be obtained by controlled rolling processes. Mechanical properties increase with increasing the amount of deformation because of the stabilization of retained austenite. Ultimate tensile strength (σb), total elongation (δ)36% and 28476 MPa%, respectively) at optimal processes.

  15. Contribution to the influence of selected alloy elements on the strain cycling and creep behaviour of cast iron with spheroidal graphite at temperatures above 450 C; Beitrag zum Einfluss ausgewaehlter Legierungselemente auf das Dehnwechsel- und Zeitstandverhalten von Gusseisen mit Kugelgraphit bei Temperaturen oberhalb 450 C

    Energy Technology Data Exchange (ETDEWEB)

    Michel, Susanne

    2012-02-15

    In this report for the first time an all-embracing databases was raised about the correlation of microstructure and high temperature mechanical properties concerning spheroidal cast iron at temperatures above 450 C. Its basic concept is a systematic variation of alloying elements and benchmarking fatigue and creep behavior of all created heats as a function of microstructure and alloys.

  16. The bainite transformation and the carbide precipitation of 4.88% aluminium austempered ductile iron investigated using electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kiani-Rashid, A.R. [Department of Materials Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, P.O. Box 91775-1111, Mashhad (Iran, Islamic Republic of)], E-mail: fkiana@yahoo.com

    2009-04-17

    The transformation to a bainitic microstructure during austempering under different conditions was examined for the most successful of the experimental casts. Austenitising temperature of 920 deg. C and austempering temperature of 350 deg. C for different holding times have been used. Microstructures have been examined by SEM and transmission electron microscopy (TEM). It was found that isothermal transformation at 350 deg. C for different soaking times gave a typical bainitic microstructure that increased with increasing austempering time. Extension of isothermal transformation time leads to precipitation of carbides which also depended on the bainitic phase transformation.

  17. Spheroidal Degeneration of the Cornea

    Directory of Open Access Journals (Sweden)

    Erdem Dinç

    2011-08-01

    Full Text Available A thirty-one-year-old male patient presented with bilateral epiphora and stinging sensation in the cornea. Detailed history revealed that a bilateral corneal scraping had been made regarding the initial diagnosis of fungal keratitis. His bestcorrected visual acuities were 20/20 and 20/30 in right and left eyes, respectively. Biomicroscopy showed bilateral amber colored spherules in the anterior stroma of the central cornea. The diagnosis of spheroidal corneal degeneration was established and symptomatic therapy with artificial tear drops was prescribed. Ultraviolet light is widely accepted to be the main etiological factor in the pathogenesis of spheroidal degeneration. Because of difficulties in the early stages of the diagnostic process of the disease, incorrect diagnoses can be made with inappropriate interventions. (Turk J Ophthalmol 2011; 41: 264-6

  18. Parametric Dwarf Spheroidal Tidal Interaction

    CERN Document Server

    Fleck, J J; Fleck, Jean-Julien; Kuhn, Jeff R.

    2003-01-01

    The time dependent tidal interaction of the Local Group Dwarf Spheroidal (dS) Galaxies with the Milky Way (MW) can fundamentally affect their dynamical properties. The model developed here extends earlier numerical descriptions of dS-MW tidal interactions. We explore the dynamical evolution of dS systems in circular or elliptical MW orbits in the framework of a parametric oscillator. An analytic model is developed and compared with more general numerical solutions and N-body simulation experiments.

  19. COMPUTER PROCESSING OF MICROSTRUCTURES OF IRON WITH DIFFERENT INCLUSIONS AMOUNTS OF LAMELLAR AND SPHERICAL GRAPHITE

    Directory of Open Access Journals (Sweden)

    A. N. Chichko

    2013-01-01

    Full Text Available Based on cast iron microstructures with different amounts of impurities of plastic and nodular graphite given in CCITT 3443-87 “Cast iron with various forms of graphite. Methods for determining the structure “shows the possibilities of automated quantitative analysis of microstructures SG2, PG4, PG6, PG10, PG12 (Plastic Box and SHG2, SHG4, SHG6, SHG10, SHG12 (spheroidal graphite, which allows the development of methods for the determination of impurities of plastic and spherical graphite according to the microstructures image under the light microscope.

  20. Study of mechanical, physical, and corrosion behavior of 0.5% cobalt alloyed austempered ductile iron

    Science.gov (United States)

    Abdullah, Bulan; Jaffar, Ahmed; Alias, Siti Khadijah; Ramli, Abdullah; Izham, Mohd Faizul

    2010-03-01

    Objectives: The purpose of this research was to determine the mechanical properties and corrosion behavior of 0.5% Co-DI before and after heat treatment and compare with commercial ductile iron. Methods: Molten metal of newly developed ductile iron which alloyed with 0.5% Cobalt produced through CO2 sand casting method. The specimens then performed preheat to 500°C in an hour then oil quenched. Specimens then performed annealing to 900°C in half an hour before oil quenched again. 500°C, 600°C and 700°C austempering temperature had been selected subjected to the specimens in half an hour before cooled to room temperature. The tests involved are microstructure analysis which included nodule count and phase analysis, polarization test, spectrometer test, density test, tensile test (ASTM E 8M), hardness test and impact test (ASTM A327) on as cast and austempered specimen. Results: 0.5% Cobalt alloyed austempered ductile iron with 500°C austempered temperature is the optimum temperature for 0.5% Co-ADI. It's not only increase the nodule count in the content, but also improve the mechanical properties such as impact toughness and tensile strength. Corrosion rate of 0.5% Co-DI also improved compare to unalloyed DI.

  1. Microstructural investigation of austempered ductile irons with ultrasonic method; Ultraschall-Gefuegeuntersuchungen von zwischenstufenverguetetem Sphaeroguss

    Energy Technology Data Exchange (ETDEWEB)

    Topuz, A. [Yildiz Technical Univ., Istanbul (Turkey). Metallurgical Engineering Dept.; Topcu, E. [Yildiz Technical Univ., Istanbul (Turkey). Metallurgical Engineering Dept.; Bakkaloglu, A. [Yildiz Technical Univ., Istanbul (Turkey). Metallurgical Engineering Dept.; Marsoglu, M. [Yildiz Technical Univ., Istanbul (Turkey). Metallurgical Engineering Dept.

    1997-06-01

    In this study, the relationship between the matrix structure and the sonic velocity of ductile iron in the as-cast and austempered heat treatment conditions was investigated. The sonic velocity in 12 different ductile irons (unalloyed, alloyed with Ni, Mo, Cu, Ni+Cu and Ni+Mo+Cu) has been measured in the as-cast condition and austempered conditions. The investigations have shown that cast iron that should meet the minimum specification of 90% nodularity requires the minimum velocity of 5680 m/s in the as-cast condition and 5450 m/s in the at 235 C austempered condition. From experimental data the equation CT{sup a}=B has been found for austempered conditions. (orig.) [Deutsch] In der vorliegenden Arbeit wurde der Zusammenhang zwischen dem Matrixgefuege und der Schallgeschwindigkeit von Sphaeroguss im Guss- und Zwischenstufenverguetungszustand untersucht. Die Schallgeschwindigkeit wurde in 12 verschiedenen Proben aus Sphaeroguss (unlegiert, legiert mit Ni, Mo, Cu, Ni+Cu und Ni+Mo+Cu) im gegossenen und vergueteten Zustand gemessen. Die Untersuchungen ergaben, dass Gusseisen mit einem Grad der Sphaerolitbildung von mindestens 90% die geringste Schallgeschwindigkeit von 5680 m/s im Gusszustand und 5450 m/s im zwischenstufenvergueteten Zustand erreichte. Aus den experimentellen Ergebnissen wurde die Formel CT{sup a}=B fuer den zwischenstufenvergueteten Zustand errechnet. (orig.)

  2. Influence of austenization temperature on the erosion behavior of austempered ductile irons

    Institute of Scientific and Technical Information of China (English)

    L.C.Chang; I.C.Hsui; L.H.Chen; S.T.Lui

    2008-01-01

    The erosion behavior of austempered ductile irons austenized at different temperatures was studied. The results indicate that the erosion rate well correlates with the mechanical properties. At high impact angles, increasing ductility and mechanical energy density results in decreasing erosion rate, whereas increasing hardness reduces the erosion rate at low impact angles.

  3. Effect of tempering treatment on toughness of austempered ductile iron; Austemper kyujo kokuen chutetsu no jinsei ni oyobosu yakimodoshi no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, S.; Kobayashi, T. [Toyohashi University of Technology, Aichi (Japan)

    1994-07-25

    Austempered ductile iron (ADI) is increasing its application to high strength members as a cast iron material that has both high strength and ductility. In order to investigate the effect of internal strain generated during austempering treatment, the present study investigates the effect of tempering on its toughness, and performs metal structural discussions. The result may be summarized as follows: the cause to bring about change in toughness given by the tempering is mainly the increase or decrease in the ductility, and the optimal tempering condition was found 723K {times} 10 min in the present study; the tempering process of ADI consists of two stages, whereas in the first stage the dislocation of high density introduced by the austempering treatment is reduced mainly in the ferrite, and the toughness improves as a result of increased ductility; in the second stage, deposition of carbide (Fe3C) is developed in association with decomposition of the residual austenite, when the toughness decreases. 18 refs., 11 figs., 1 tab.

  4. Effects of Copper and Austempering on Corrosion Behavior of Ductile Iron in 3.5 Pct Sodium Chloride

    Science.gov (United States)

    Hsu, Cheng-Hsun; Lin, Kuan-Ting

    2013-10-01

    Although alloying and heat treatments are common industrial practices to obtain ductile irons with desired mechanical properties, related information on how the two practices affect corrosion behavior is scarce. In this study, two ductile irons—with and without 1 wt pct copper addition—were austempered to obtain austempered ductile irons (ADIs). Polarization tests and salt spray tests were conducted to explore how both copper-alloying and austempering heat treatments influenced the corrosion behavior of ductile irons. The results showed that the corrosion resistance of 1 wt pct copper-alloyed ductile iron was better than that of the unalloyed one, while ADI had improved corrosion resistance compared with the as-cast. In particular, the ductile iron combined with the copper-alloying and austempering treatments increased the corrosion inhibition efficiency up to 84 pct as tested in 3.5 wt pct NaCl solution.

  5. Effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron

    Institute of Scientific and Technical Information of China (English)

    S. Yazdani; M. Ardestani

    2007-01-01

    The effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron has been investigated. Austempering of samples was performed at 325 ℃ and 400 ℃after austenitizing at 875 ℃ and 950 ℃. The sub-zero treatments were carried out by cooling down the samples to -30 ℃, -70 ℃ and -196 ℃. The changes in volume fraction of austenite and mechanical properties were determined after cooling to each temperature. The austenite volume fraction of samples which were austenitized at 875 ℃ and austempered at 325 ℃ remained unchanged, whilst it reduced in samples austenitized at 950 ℃ and 875 ℃ for austempering temperature of 400 ℃. In these specimens, some austenite transformed to martensite after subzero cooling. Mechanical property measurements showed a slight increase in strength and hardness and decrease in elongation and toughness due to this transformation behavior.

  6. Effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron

    Directory of Open Access Journals (Sweden)

    M. Ardestani

    2007-05-01

    Full Text Available The effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron has been investigated. Austempering of samples was performed at 325! and 400℃ after austenitizing at 875℃ and 950℃. The sub-zero treatments were carried out by cooling down the samples to -30℃, -70℃ and -196℃. The changes in volume fraction of austenite and mechanical properties were determined after cooling to each temperature. The austenite volume fraction of samples which were austenitized at 875℃ and austempered at 325℃ remained unchanged, whilst it reduced in samples austenitized at 950℃ and 875℃ for austempering temperature of 400℃. In these specimens, some austenite transformed to martensite after subzero cooling. Mechanical property measurements showed a slight increase in strength and hardness and decrease in elongation and toughness due to this transformation behavior.

  7. Scalable robotic biofabrication of tissue spheroids

    Energy Technology Data Exchange (ETDEWEB)

    Mehesz, A Nagy; Hajdu, Z; Visconti, R P; Markwald, R R; Mironov, V [Advanced Tissue Biofabrication Center, Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC (United States); Brown, J [Department of Mechanical Engineering, Clemson University, Clemson, SC (United States); Beaver, W [York Technical College, Rock Hill, SC (United States); Da Silva, J V L, E-mail: mironovv@musc.edu [Renato Archer Information Technology Center-CTI, Campinas (Brazil)

    2011-06-15

    Development of methods for scalable biofabrication of uniformly sized tissue spheroids is essential for tissue spheroid-based bioprinting of large size tissue and organ constructs. The most recent scalable technique for tissue spheroid fabrication employs a micromolded recessed template prepared in a non-adhesive hydrogel, wherein the cells loaded into the template self-assemble into tissue spheroids due to gravitational force. In this study, we present an improved version of this technique. A new mold was designed to enable generation of 61 microrecessions in each well of a 96-well plate. The microrecessions were seeded with cells using an EpMotion 5070 automated pipetting machine. After 48 h of incubation, tissue spheroids formed at the bottom of each microrecession. To assess the quality of constructs generated using this technology, 600 tissue spheroids made by this method were compared with 600 spheroids generated by the conventional hanging drop method. These analyses showed that tissue spheroids fabricated by the micromolded method are more uniform in diameter. Thus, use of micromolded recessions in a non-adhesive hydrogel, combined with automated cell seeding, is a reliable method for scalable robotic fabrication of uniform-sized tissue spheroids.

  8. Thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

    2011-01-01

    A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

  9. Estudio experimental sobre el comportamiento del hierro austemperado nitrurado (adi a la fatiga de contacto. // Experimental study to contact fatigue behavior of nitrided-austempered ductile iron.

    Directory of Open Access Journals (Sweden)

    C. Figueroa

    2001-10-01

    on the surface were observed in a scanning electron microscope (SEM.The results indicated that the white nitrided layer from 5 to 6 μm deep on ADI disappeared during the contact fatigue tests.Also it was confirmed the decrease of the endurance limit of nitrided ADI for the lowest Hertzian pressures. Moreover itwas detected that the graphite nodules act as a barrier to propagation of cracks.Key words: Contact fatigue, nitrided layer, austempered ductile iron, discs test machine.

  10. Microstructure transformation during plastic deformation of the austempered ductile iron

    Directory of Open Access Journals (Sweden)

    D. Myszka

    2009-01-01

    Full Text Available Excellent properties of ADI (Austempered Ductile Iron are widely praised by the world technical literature. These properties depend onthe cast iron microstructure formed during the heat treatment process of a specific type. The matrix of ADI is a mixture of lamellar ferrite and high-carbon austenite. It seems, however, that it is the austenite that is responsible for the high strength and ductility of this material, although investigations and analyses have proved that it is not homogeneous. Various types of austenite found in the ADI matrix include unreacted austenite, stable austenite, and metastable austenite which will be transferred into martensite during machining of castings.In this study an attempt has been made to determine the fraction of metastable austenite and to evaluate its effect on ADI properties.The heat treatment enabled manufacturing ADI characterised by the following properties: T.S.>1000MPa, El.>10%, Y.S.>600MPa. As anext step, the controlled process of plastic deformation of the samples was carried out. Applying the new method it has been established that due to 15% cold work, the structure of the examined ADI contains 9% of martensite; this volume fraction goes up to 17% after 25% cold work. The results of the investigations were cofirmed by X-ray diffraction pattern analysis and magnetic measurements.Consequently, it has been proved that ADI characterised by properties satisfying the criteria of an international standard developed for this particular material contains a large amount of metastable austenite subject to the TRIP (Transformation Induced Plasticity effect.

  11. Bridged graphite oxide materials

    Science.gov (United States)

    Herrera-Alonso, Margarita (Inventor); McAllister, Michael J. (Inventor); Aksay, Ilhan A. (Inventor); Prud'homme, Robert K. (Inventor)

    2010-01-01

    Bridged graphite oxide material comprising graphite sheets bridged by at least one diamine bridging group. The bridged graphite oxide material may be incorporated in polymer composites or used in adsorption media.

  12. Constrained spheroids for prolonged hepatocyte culture.

    Science.gov (United States)

    Tong, Wen Hao; Fang, Yu; Yan, Jie; Hong, Xin; Hari Singh, Nisha; Wang, Shu Rui; Nugraha, Bramasta; Xia, Lei; Fong, Eliza Li Shan; Iliescu, Ciprian; Yu, Hanry

    2016-02-01

    Liver-specific functions in primary hepatocytes can be maintained over extended duration in vitro using spheroid culture. However, the undesired loss of cells over time is still a major unaddressed problem, which consequently generates large variations in downstream assays such as drug screening. In static culture, the turbulence generated by medium change can cause spheroids to detach from the culture substrate. Under perfusion, the momentum generated by Stokes force similarly results in spheroid detachment. To overcome this problem, we developed a Constrained Spheroids (CS) culture system that immobilizes spheroids between a glass coverslip and an ultra-thin porous Parylene C membrane, both surface-modified with poly(ethylene glycol) and galactose ligands for optimum spheroid formation and maintenance. In this configuration, cell loss was minimized even when perfusion was introduced. When compared to the standard collagen sandwich model, hepatocytes cultured as CS under perfusion exhibited significantly enhanced hepatocyte functions such as urea secretion, and CYP1A1 and CYP3A2 metabolic activity. We propose the use of the CS culture as an improved culture platform to current hepatocyte spheroid-based culture systems.

  13. Thermal Stability of Austempered Ductile Iron Evaluated in a Temperature Range of 20-300K

    Directory of Open Access Journals (Sweden)

    Dawid MYSZKA

    2016-05-01

    Full Text Available The aim of this article was to determine through changes in magnetic properties the stability of the austempered ductile iron (ADI microstructure during temperature changes in a range of 20 – 300 K. The measurements were taken in a vibrating sample magnetometer (VSM using Fe27Ni2TiMoAlNb austenitic stainless steel and four types of austempered ductile iron obtained under various heat treatment conditions. The plotted curves showing changes in the magnetisation degree as a function of temperature had a number of characteristic points illustrating changes taking place in the microstructure. For each of the materials examined, the martensite start temperature Ms and the temperature range within which the martensitic transformation takes place were identified.

  14. The abrasion and impact-abrasion behavior of austempered ductile irons

    Energy Technology Data Exchange (ETDEWEB)

    Hawk, Jeffrey A.; Dogan, Omer N.; Lerner, Y.S. (University of Northern Iowa)

    1998-01-01

    Austempering of ductile irons has led to a new class of irons, Austempered Ductile Irons (ADIs), with improved mechanical strength and fracture toughness lacking in gray cast irons. Laboratory wear tests have been used to evaluate the abrasive and impact-abrasive wear behavior of a suite of ADIs. The use of high-stress, two-body abrasion, low-stress, three-body abrasion, and impact-abrasion tests provides a clear picture of the abrasive wear behavior of the ADIs and the mechanisms of material removal. When combined with hardness measurements, fracture toughness and a knowledge of the microstructure of the ADIs, the overall performance can be assessed relative to more wear resistant materials such as martensitic steels and high-chromium white cast irons

  15. Thermal Stability of Austempered Ductile Iron Evaluated in a Temperature Range of 20-300K

    Directory of Open Access Journals (Sweden)

    Dawid MYSZKA

    2016-05-01

    Full Text Available The aim of this article was to determine through changes in magnetic properties the stability of the austempered ductile iron (ADI microstructure during temperature changes in a range of 20 – 300 K. The measurements were taken in a vibrating sample magnetometer (VSM using Fe27Ni2TiMoAlNb austenitic stainless steel and four types of austempered ductile iron obtained under various heat treatment conditions. The plotted curves showing changes in the magnetisation degree as a function of temperature had a number of characteristic points illustrating changes taking place in the microstructure. For each of the materials examined, the martensite start temperature Ms and the temperature range within which the martensitic transformation takes place were identified.

  16. Effect of heat treatment on the thermal expansion coefficient of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Tadayon saidi, M. [Dept. Metallurgy-Karaj Azad Univ.-Karaj (Iran); Baghersaie, N. [Tehran Center, Control Dept., Eng. Research Inst., Ministry of Jihad Agriculture (Iran); Varahram, N. [RAZI Metallurgical Research Inst.-Tehran (Iran)

    2005-07-01

    Austempered ductile iron provide a unique combination of strength and toughness coupled with excellent design flexibility for automotive application as compared to forged or cast steels. Some material properties such as thermal expansion coefficient and its influence in final machining tolerance is a matter of discussion in the automotive industry. In this study the effect of heart treatment cycle on the microstructure and thermal expansion of ADI was investigated. Samples were austempered at 275 C and 375 C for one hour and then dilatometric test carried out in the temperature range of 50 C to 350 C, then the result was compared with the thermal expansion coefficient of forged steel. Microstructure and mechanical investigations were used to the assurance of these results. The results indicate that replacing of forged steel with ADI due to lower cost production and reduction in weight is possible if the correct tolerance were selected. (orig.)

  17. Magnetic-directed patterning of cell spheroids.

    Science.gov (United States)

    Whatley, Benjamin R; Li, Xiaowei; Zhang, Ning; Wen, Xuejun

    2014-05-01

    We have described an approach to fabricate three-dimensional (3D) cell-based structures using functionalized super paramagnetic iron oxide nanoparticles (SPIONs) as patterning agents to guide the assembly of endothelial cell spheroids into 3D patterns using the magnetic forces generated by a prefabricated magnetic template. SPIONs were first uptaken by endothelial cells before they were assembled into uniform-sized spheroids through a home-made robotic spheroid maker. To guide the magnetic spheroids, a unique magnetic template was fabricated using computer-aided design and cut from a magnetic sheet. The spheroids were then guided to the prefabricated magnetic template through the attractive magnetic forces between the SPIONs inside the endothelial cells and the magnetic template. Fusion of endothelial cell spheroids over time while adhered to the magnetic template allowed for the formation of 3D cell-based structures. Subsequent removal of the prefabricated magnetic template left 3-D endothelial cell sheets, which may be stacked to fabricate complicated 3D multicellular tissue structures. To enhance the cytocompatibility, SPIONs were silica-coated before use. At low concentrations, the SPIONs did not adversely affect cell viability, proliferation, and phenotype stability. Light and confocal microscopy showed that endothelial cell spheroids could be reproducibly created with high uniformity. The endothelial cells were able to remain viable and maintain the 3D structure in vitro. We have proved the concept to use SPIONs as a patterning agent to direct the attachment and self assembly of SPION-loaded endothelial cell spheroids on a prefabricated magnetic template for the formation of 3D cell based structures. A magnetic-directed technique allows quick patterning of cell spheroids in accordance with desirable magnetic patterns, therefore, holding promise for scalable fabrication of complicated 3D multicellular tissue structures. By varying the cell types and the

  18. Bistable flows in precessing spheroids

    CERN Document Server

    Cébron, D

    2015-01-01

    Precession driven flows are found in any rotating container filled with liquid, when the rotation axis itself rotates about a secondary axis that is fixed in an inertial frame of reference. Because of its relevance for planetary fluid layers, many works consider spheroidal containers, where the uniform vorticity component of the bulk flow is reliably given by the well-known equations obtained by Busse in 1968. So far however, no analytical result on the solutions is available. Moreover, the cases where multiple flows can coexist have not been investigated in details since their discovery by Noir et al. (2003). In this work, we aim at deriving analytical results on the solutions, aiming in particular at, first estimating the ranges of parameters where multiple solutions exist, and second studying quantitatively their stability. Using the models recently proposed by Noir \\& C{\\'e}bron (2013), which are more generic in the inviscid limit than the equations of Busse, we analytically describe these solutions, ...

  19. Influence of cooling conditions and amount of retained austenite on the fracture of austempered ductile iron

    Directory of Open Access Journals (Sweden)

    VYACHESLAV GORYANY

    2008-01-01

    Full Text Available SEM Analysis of fracture surfaces from tensile test specimens of thick-walled, austempered ductile irons (diameter 160 mm shows different fracture behavior depending on the austenite retained in the matrix. The results show ductile fractures only in areas containing retained austenite sections. In section areas without or with a very low content of retained austenite, only brittle fracture without any plastic deformation occurs. The content of retained austenite determines the amount of ductile fracture in the microstructure.

  20. The effect of alloy elements on the microstructure and properties of austempered ductile irons

    Energy Technology Data Exchange (ETDEWEB)

    Lin, B.Y.; Chen, E.T.; Lei, T.S. [National Taiwan Institute of Technology, Taipei (Taiwan, Province of China). Dept. of Mechanical Engineering

    1995-05-01

    Ductile cast iron has already demonstrated excellent mechanical properties. If given proper austempering, it can exhibit even more outstanding characteristics. The process of austempering for ductile cast iron is similar to steel, and requires an adequate completely, and then rapidly quenching the austenitizing temperature allowing the matrix of ductile iron to be austenitized completely, and then rapidly quenching the austenitized ductile iron down to 300 C--400 C. Caution is required to prevent austenite from transforming into proeutectoid ferrite or pearlite. Finally, the ductile iron must be kept in an isothermal condition for a proper length of time. Many kinds of experimental techniques such as quantitative metallography, magnetic change, dilatometry, X-ray diffraction, electrical resistivity change etc., may be used to measure the phase transformation during the austempering of ductile irons. However, the method of measuring the change of electrical resistivity, not only provides continuous and complete data, but also the time to start and to finish for both stages of the reaction can be significantly determined. In this paper, the effect of alloy elements on the microstructure and property of ADI was investigated. First, the specimens containing Mn, Cu, Ni and Mo were made separately, then a PC-controlled vacuum heat treating system was used for the heat treatments.

  1. Ameliorated Austenite Carbon Content Control in Austempered Ductile Irons by Support Vector Regression

    Directory of Open Access Journals (Sweden)

    Chan-Yun Yang

    2013-01-01

    Full Text Available Austempered ductile iron has emerged as a notable material in several engineering fields, including marine applications. The initial austenite carbon content after austenization transform but before austempering process for generating bainite matrix proved critical in controlling the resulted microstructure and thus mechanical properties. In this paper, support vector regression is employed in order to establish a relationship between the initial carbon concentration in the austenite with austenization temperature and alloy contents, thereby exercising improved control in the mechanical properties of the austempered ductile irons. Particularly, the paper emphasizes a methodology tailored to deal with a limited amount of available data with intrinsically contracted and skewed distribution. The collected information from a variety of data sources presents another challenge of highly uncertain variance. The authors present a hybrid model consisting of a procedure of a histogram equalizer and a procedure of a support-vector-machine (SVM- based regression to gain a more robust relationship to respond to the challenges. The results show greatly improved accuracy of the proposed model in comparison to two former established methodologies. The sum squared error of the present model is less than one fifth of that of the two previous models.

  2. Microstructures and Mechanical Properties of Austempering SUS440 Steel Thin Plates

    Directory of Open Access Journals (Sweden)

    Cheng-Yi Chen

    2016-02-01

    Full Text Available SUS440 is a high-carbon stainless steel, and its martensite matrix has high heat resistance, high corrosion resistance, and high pressure resistance. It has been widely used in mechanical parts and critical materials. However, the SUS440 martempered matrix has reliability problems in thin plate applications and thus research uses different austempering heat treatments (tempering temperature: 200 °C–400 °C to obtain a matrix containing bainite, retained austenite, martensite, and the M7C3 phase to investigate the relationships between the resulting microstructure and tensile mechanical properties. Experimental data showed that the austempering conditions of the specimen affected the volume fraction of phases and distribution of carbides. After austenitizing heat treatment (1080 °C for 30 min, the austempering of the SUS440 thin plates was carried out at a salt-bath temperature 300 °C for 120 min and water quenching was then used to obtain the bainite matrix with fine carbides, with the resulting material having a higher tensile fracture strength and average hardness (HRA 76 makes it suitable for use as a high-strength thin plate for industrial applications.

  3. Machinability of Austempered Ductile Iron (ADI) Produced by Integrated Green Technology of Continuous Casting-Heat Treatment Processes

    Science.gov (United States)

    Meena, A.; El Mansori, M.; Ghidossi, P.

    2011-01-01

    This study presents the novel processing technique known as continuous casting-heat treatment processes to produce Austempered Ductile Iron (ADI) which is a new class of ductile iron. ADI is characterized by improved mechanical properties but has low machinability as compared to other cast irons and steel of similar strength. The novel technique is developed by the integration of casting (in die casting) and heat treatment processes in foundry to save cost energy and time. Specimens just after casting were austenitized at 930° C for 90 min and then austempered in fluidized bed at 380° C for 90 and 120 min. Hence, the effect of austempering time on the morphology of retained austenite and mechanical properties of the material were examined and compared with conventionally produced ADI. Drilling tests were then carried out to evaluate the machinability of ADI in terms of cutting forces, chip micro-hardness, chip morphology and surface roughness. The mechanical properties of ADI austempered for 120 min have found to be better as compare to the ADI austempered for 90 min.

  4. Conjunctival spheroid degeneration. Recurrence after excision.

    Science.gov (United States)

    Norn, M S

    1982-06-01

    After excision of part of the conjunctiva in 15 eyes (14 subjects) due to spheroid degeneration, the author noticed only fairly small, varying numbers of autofluorescent and colourless spheroids-after an observation period of 18 months, only 6% of autofluorescent and 13% of colourless bodies were observed compared to the number before biopsy. Around the biopsy site only a few spheroids were seen, with a non-significant tendency to increase in number of the colourless bodies. In the cornea the band-shaped keratopathy had aggravated, with the formation of a small number of large, autofluorescent spheroids. A pinguecula recurred in a mild degree only in 3 out of 13 cases within 18 months.

  5. The Effect of Isothermal Heat Treatment Time on the Microstructure and Properties of 2.11% Al Austempered Ductile Iron

    Science.gov (United States)

    Erfanian-Naziftoosi, H. R.; Haghdadi, N.; Kiani-Rashid, A. R.

    2012-08-01

    In this article, the bainitic transformation during austempering was studied for a 2.11% Al containing ductile iron under different isothermal holding times. The austenitizing time and temperature were selected to be 60 min and 920 °C, respectively, referring to previous studies. The isothermal austempering heat treatments were performed at 350 °C for different durations. Microstructures have been examined by optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microstructural investigations revealed that austempering treatment at 350 °C for durations up to 100 min results in microstructures consisting of carbide-free bainitic ferrite with considerable amounts of retained austenite while the extension of isothermal transformation time leads to precipitation of carbides. Hardness measurements were also carried out the results of which were shown to be consistent with microstructural evolutions.

  6. Effect of laser surface hardening on the microstructure, hardness and residual stresses of austempered ductile iron grades

    Energy Technology Data Exchange (ETDEWEB)

    Soriano, C., E-mail: csoriano@tekniker.es [Tekniker-IK4, Manufacturing Processes Department, Avda. Otaola 20, CP-20600, Eibar (Gipuzkoa) (Spain); Leunda, J.; Lambarri, J.; Garcia Navas, V.; Sanz, C. [Tekniker-IK4, Manufacturing Processes Department, Avda. Otaola 20, CP-20600, Eibar (Gipuzkoa) (Spain)

    2011-06-01

    A study of the laser surface hardening process of two austempered ductile iron grades, with different austempering treatments has been carried out. Hardening was performed with an infrared continuous wave Nd:YAG laser in cylindrical specimens. The microstructure of the laser hardened samples was investigated using an optical microscope, microhardness profiles were measured and surface and radial residual stresses were studied by an X-ray diffractometer. Similar results were achieved for both materials. A coarse martensite with retained austenite structure was found in the treated area, resulting in a wear resistant effective layer of 0.6 mm to 1 mm with a microhardness between 650 HV and 800 HV. Compressive residual stresses have been found at the hardened area being in agreement with the microhardness and microstructural variations observed. The achieved results point out that the laser surface hardening is a suitable method for improving the mechanical properties of austempered ductile irons.

  7. Manganese in dwarf spheroidal galaxies

    CERN Document Server

    North, P; Jablonka, P; Hill, V; Shetrone, M; Letarte, B; Lemasle, B; Venn, K A; Battaglia, G; Tolstoy, E; Irwin, M J; Primas, F; Francois, P

    2012-01-01

    We provide manganese abundances (corrected for the effect of the hyperfine structure) for a large number of stars in the dwarf spheroidal galaxies Sculptor and Fornax, and for a smaller number in the Carina and Sextans dSph galaxies. Abundances had already been determined for a number of other elements in these galaxies, including alpha and iron-peak ones, which allowed us to build [Mn/Fe] and [Mn/alpha] versus [Fe/H] diagrams. The Mn abundances imply sub-solar [Mn/Fe] ratios for the stars in all four galaxies examined. In Sculptor, [Mn/Fe] stays roughly constant between [Fe/H]\\sim -1.8 and -1.4 and decreases at higher iron abundance. In Fornax, [Mn/Fe] does not vary in any significant way with [Fe/H]. The relation between [Mn/alpha] and [Fe/H] for the dSph galaxies is clearly systematically offset from that for the Milky Way, which reflects the different star formation histories of the respective galaxies. The [Mn/alpha] behavior can be interpreted as a result of the metal-dependent Mn yields of type II and ...

  8. Efecto del conteo de nódulos en la resistencia a la tracción de los hierros dúctiles austemperados. // Effect of nodules count in the tensile strength of austempered ductile irons.

    Directory of Open Access Journals (Sweden)

    C. J. Diez Cicero

    2004-01-01

    Full Text Available Entre los materiales metálicos de mayor demanda, la producción de hierro con grafito nódular ocupa uno de los lugaresmás importantes entre los hierros fundidos de alta resistencia y con la introducción del tratamiento térmico deaustemperado, aplicado a estas fundiciones, se da lugar a una nueva familia de materiales, caracterizados por su altaresistencia mecánica y elevada tenacidad, que mantienen la economía y facilidad de producción de las fundicionesnodulares.Este trabajo, hace una valoración del comportamiento de hierros nodulares, con diferentes conteos de nódulos, a los que lesfue aplicado el tratamiento de austemperado y posteriormente se les sometió a ensayos de propiedades mecánicas detracción.Con los resultados obtenidos, se hace un análisis de la influencia del conteo de nódulos en dichas propiedades, así comotambién, de la interrelación del conteo de nódulos con las variables de tratamiento térmico utilizadas en las muestrasensayadas.Palabras claves: Hierro nódular, conteo de nódulos, austemperado.____________________________________________________________________________Abstract.At the present, iron production with nodular graphite, occupies one of the most important places in the production ofmetallic materials high resistance. The introduction of the austempered heat treatment, gives rise to a new family ofmaterials, characterized by its high mechanical resistance and elevated tenacity, this family maintain the economy andfacility of production of the smeltings nodules. This work, makes a valuation of the nodules iron behavior, with differentnumber of nodules, to which the austempered treatment was applied, in order to test mechanical properties. With theobtained results, an analysis is carriewd out to control the influence of the count of nodules in these properties, as well as,the interrelation of the count of nodules with the used heat treatment variables in the samples.Key words: nódular Iron, count of

  9. Effects of heat treatment on toughness of austempered ductile cast iron with Cu and Ni; Cu-Ni tenka osutenpa chutetsu no jinsei ni oyobosu netsushori no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Aoyama, M.; Takatsu, M.; Takagi, H

    1998-08-25

    The alloying of ductile cast iron with Cu and Ni is effective for the structural control in austemper heat treatment. Use of this type of cast iron is provided to produce cast iron materials with extremely high toughness and strength. In this study, the effects of austempering conditions and the addition of Cu and Ni on toughness of ductile cast iron are investigated. In austemper heat treatment, impact absorbed energy is increased by raising the austempering temperature. However, at high austempering temperatures exceeding 3.6 ks at 673K, the formation of fine pearlite proceeded, resulting in a marked decrease in the impact absorbed energy. Addition of Cu-Ni in the cast iron resulted in greater impact absorbed energy and tensile strength at any temperature during the austempering treatment. It depends on the suppression of precipitation beginning of fine pearlite and the stabilization of retained austenite. Furthermore, this cast iron alloy reduced the change in impact absorbed energy and tensile strength, induced during the austempering time. 15 refs., 12 figs., 1 tab.

  10. Statistical Assessment of the Impact of Elevated Contents of Cu and Ni on the Properties of Austempered Ductile Iron

    Directory of Open Access Journals (Sweden)

    Nawrocki P.

    2016-12-01

    Full Text Available The article presents a statistical analysis of data collected from the observation of the production of austempered ductile iron. The impact assessment of the chemical composition, i.e. high contents of Cu and Ni on the properties of ductile iron isothermal tempered is critical to find the right chemical composition of austempered ductile iron. Based on the analyses range of the percentage of Cu and Ni which were selected in the cast iron to obtain material with high strength properties.

  11. Redistribution and Effect of Various Elements on the Morphology of Primary Graphite in Cast Iron

    Directory of Open Access Journals (Sweden)

    J. Lacaze

    2013-01-01

    Full Text Available It has been shown repeatedly that many elements present as traces or at low level can affect graphite shape in cast irons. As part of a long term project aimed at clarifying the growth and the alteration of spheroidal graphite, a study on the effect of a few elements (Cu, Sn, Sb, and Ti on primary graphite growth was undertaken and analysed with reference to an alloy without any such additions. This work was performed by remelting alloys in graphite crucibles thus saturating the melt in carbon and enabling primary graphite to grow by controlled cooling of the melt above the eutectic temperature. Primary graphite growth in the reference alloy was observed to be lamellar, while the added elements were found to affect bulk graphite and to modify its outer shape, with Sb leading eventually to rounded agglomerates together with wavy lamellae. Secondary ion mass spectrometry was used to analyze the distribution of elements, and no build-up of trace elements at the graphite surface could be observed. Instead, it is established that the perturbation of bulk graphite is associated with inhomogeneous distribution of metallic elements inside graphite precipitates.

  12. Graphite Technology Development Plan

    Energy Technology Data Exchange (ETDEWEB)

    W. Windes; T. Burchell; M.Carroll

    2010-10-01

    The Next Generation Nuclear Plant (NGNP) will be a helium-cooled High Temperature Gas Reactor (HTGR) with a large graphite core. Graphite physically contains the fuel and comprises the majority of the core volume. Graphite has been used effectively as a structural and moderator material in both research and commercial high-temperature gas-cooled reactors. This development has resulted in graphite being established as a viable structural material for HTGRs. While the general characteristics necessary for producing nuclear grade graphite are understood, historical “nuclear” grades no longer exist. New grades must be fabricated, characterized, and irradiated to demonstrate that current grades of graphite exhibit acceptable non-irradiated and irradiated properties upon which the thermomechanical design of the structural graphite in NGNP is based. This Technology Development Plan outlines the research and development (R&D) activities and associated rationale necessary to qualify nuclear grade graphite for use within the NGNP reactor.

  13. The effect of segregation on the austemper transformation and toughness of ductile irons

    Science.gov (United States)

    Lin, B. Y.; Chen, E. T.; Lei, T. S.

    1998-06-01

    The effect of segregation of alloying elements on the phase transformation of ductile iron during austempering was investigated. Four heats, each containing 0.4%Mn, 1% Cu, 1.5% Ni, or 0.4% Mo (wt%) separately, were melted; then three different sizes of casting bars (3,15, and 75 mm diameter) were poured from each heat. The distribution and the degree of segregation of certain elements were quantitatively analyzed using an electron microprobe. A personal computer (PC)-controlled heat treating system was used to measure electrical resistivity, and the information on resistivity variations was used to analyze the effect of segregation on phase transformations during austempering. Also, Charpy impact and Rockwell hardness tests were performed to determine the effect of segregation on properties. Results of the electron microprobe analysis showed that the degree of segregation of alloy elements increases with an increase in diameter of the casting bars (i.e., an increase of solidification time of castings). The degree of segregation of alloy elements, represented by segregation ratio (SR) (the maximum concentration of element in cell divided by the minimum concentration of element in cell), varied linearly with the casting modulus (M) (volume of casting divided by surface area of casting). Regarding the segregating tendency among alloy elements, positive segregating elements Mn and Mo showed more segregation than the negative segregating elements Si, Cu, and Ni. In addition, segregation of Mo was more significant than Mn, and that for Cu was greater than Ni and Si. Between the time of finishing the first stage and beginning the second stage of bainite reaction in ductile irons, there is a significant “processing window,” At;, for austempering to obtain optimum mechanical properties. From the electrical resistivity data, it was observed that the austempering temperature plays a major role in the processing window. There was a narrow window at 400 ‡C but a larger

  14. A multicellular spheroid array to realize spheroid formation, culture, and viability assay on a chip.

    Science.gov (United States)

    Torisawa, Yu-suke; Takagi, Airi; Nashimoto, Yuji; Yasukawa, Tomoyuki; Shiku, Hitoshi; Matsue, Tomokazu

    2007-01-01

    We describe a novel multicellular spheroid culture system that facilitates the easy preparation and culture of a spheroid microarray for the long-term monitoring of cellular activity. A spheroid culture device with an array of pyramid-like microholes was constructed in a silicon chip that was equipped with elastomeric microchannels. A cell suspension was introduced via the microfluidic channel into the microstructure that comprised silicon microholes and elastomeric microwells. A single spheroid can be formed and localized precisely within each microstructure. Since the culture medium could be replaced via the microchannels, a long-term culture (of approximately 2 weeks) is available on the chip. Measurement of albumin production in the hepatoma cell line (HepG2) showed that the liver-specific functions were maintained for 2 weeks. Based on the cellular respiratory activity, the cellular viability of the spheroid array on the chip was evaluated using scanning electrochemical microscopy. Responses to four different chemical stimulations were simultaneously detected on the same chip, thus demonstrating that each channel could be evaluated independently under various stimulation conditions. Our spheroid culture system facilitated the understanding of spheroid formation, culture, and viability assay on a single chip, thus functioning as a useful drug-screening device for cancer and liver cells.

  15. Study of high cycle fatigue of PVD surface-modified austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Feng, H.P.; Lee, S.C.; Hsu, C.H.; Ho, J.M. [Tatung Inst. of Technol., Taipei (Taiwan, Province of China). Dept. of Mater. Eng.

    1999-05-25

    Austempered ductile iron (ADI) is made from ductile iron by an austempering treatment, and its main microstructure is ausferrite that is composed of acicular ferrite and high carbon austenite. The purpose of this experiment is to investigate the influence of different coating layers and the size of casting (mass effect) on the high-cycle fatigue properties of ADI. Specimens in two casting sizes of the same chemical composition were subjected to a high-toughness austempering treatment, then coated with TiN or TiCN hard films by a physical vapor deposition (PVD) process. The results showed that the fatigue limit of the small casting size ADI is 292 MPa for ADI coated with TiN and 306 MPa for ADI coated with TiCN, which are 16% and 22%, respectively, higher than that of the ADI without coating (251 MPa). For the large casting size ADI, the fatigue limits are 200, 214 and 217 MPa for ADI without coating, ADI coated with TiN and ADI coated with TiCN, respectively. ADI coated with TiN and with TiCN are 7% and 9% better than the uncoated. Thus, it is concluded that TiN and TiCN coatings by PVD can improve the high-cycle fatigue strength of ADI. This is due to the high surface hardness and possibly the ADI surface compressive residual stress as well. For the small casting size ADI, TiCN-coated specimens have a bit higher fatigue strengths and this might be attributed to the higher hardness of TiCN than TiN films. As to the effect of mass, it is found that the small casting size has better fatigue properties and benefits more from the coating films. This could have stemmed from the higher nodule count and its associated benefits in thinner castings. (orig.) 24 refs.

  16. Bars and spheroids in gravimetry problem

    CERN Document Server

    Sizikov, Valery

    2016-01-01

    The direct gravimetry problem is solved by dividing each deposit body into a set of vertical adjoining bars, whereas in the inverse problem, each deposit body is modelled by a homogeneous ellipsoid of revolution (spheroid). Well-known formulae for the z-component of gravitational intensity for a spheroid are transformed to a convenient form. Parameters of a spheroid are determined by minimizing the Tikhonov smoothing functional with constraints on the parameters, which makes the ill-posed inverse problem by unique and stable. The Bulakh algorithm for initial estimating the depth and mass of a deposit is modified. The proposed technique is illustrated by numerical model examples of deposits in the form of two and five bodies. The inverse gravimetry problem is interpreted as a gravitational tomography problem or, in other words, as "introscopy" of Earth's crust and mantle.

  17. Use of spheroidal models in gravitational tomography

    CERN Document Server

    Sizikov, Valery

    2015-01-01

    The direct gravimetry problem is solved using the subdivision of each body of a deposit into a set of vertical adjoining bars, and in the inverse problem each body of a deposit is modeled by a uniform ellipsoid of revolution (spheroid). Well-known formulas for z-component of gravitational intensity of a spheroid are transformed to a convenient form. Parameters of a spheroid are determined by minimizing the Tikhonov smoothing functional using constraints on the parameters. This makes the ill-posed inverse problem by unique and stable. The Bulakh algorithm for initial estimating the depth and mass of a deposit is modified. The technique is illustrated by numerical model examples of deposits in the form of two and five bodies. The inverse gravimetry problem is interpreted as a gravitational tomography problem or the intravision of the Earth's crust and mantle.

  18. Radiation damage in graphite

    CERN Document Server

    Simmons, John Harry Walrond

    1965-01-01

    Nuclear Energy, Volume 102: Radiation Damage in Graphite provides a general account of the effects of irradiation on graphite. This book presents valuable work on the structure of the defects produced in graphite crystals by irradiation. Organized into eight chapters, this volume begins with an overview of the description of the methods of manufacturing graphite and of its physical properties. This text then presents details of the method of setting up a scale of irradiation dose. Other chapters consider the effect of irradiation at a given temperature on a physical property of graphite. This

  19. Charged fluid distribution in higher dimensional spheroidal space-time

    Indian Academy of Sciences (India)

    G P Singh; S Kotambkar

    2005-07-01

    A general solution of Einstein field equations corresponding to a charged fluid distribution on the background of higher dimensional spheroidal space-time is obtained. The solution generates several known solutions for superdense star having spheroidal space-time geometry.

  20. Sulphur isotope ratios in the Canyon Diablo metallic spheroids

    Science.gov (United States)

    McEwing, C. E.; Rees, C. E.; Thode, H. G.

    1983-09-01

    Nininger (1956) has discovered metallic spheroids in the soil surrounding Meteor Crater in Arizona. Nininger suggested that the spheroids condensed from the center of a homogeneous explosion-produced metallic vapor cloud. The present investigation is concerned with measurements of sulfur contents and delta S-34 values of metallic spheroids from the vicinity of Meteor Crater. It is found that the small metallic spheroids have lower sulfur contents and higher delta S-34 values than do the large spheroids. It is concluded that the observed isotopic patterns are unlikely to have arisen during desulfurization of the metallic liquid from which the spheroids were formed or during high temperature oxidation or the spheroids. The most likely process for the production of the observed delta S-34 values and sulfur contents is low temperature oxidation reactions experienced by the spheroids during their surface exposure following formation.

  1. Influence of austempering heat treatment on mechanical and corrosion properties of ductile iron samples

    Directory of Open Access Journals (Sweden)

    M. Janjić

    2016-07-01

    Full Text Available Mechanical properties and corrosion resistance of metals are closely related to the microstructure characteristics of the material. The paper compares the results of these two sets of properties after investigating samples of base ductile iron and heat-treated samples of the base austempered ductile iron (ADI. The basic material is perlite ferritic iron alloyed with copper and nickel. To test the corrosion rate of the base material (ductile iron and the heattreated samples (ADI, electrochemical techniques of potentiostatic polarization were used (the technique of Tafel curves extrapolation and the potentiodynamic polarization technique.

  2. Effect of Cu, Mo, Si on the content of retained austenite of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Mi, Y. [Zhejiang Univ., Hangzhou (China). Dept. of Materials Science and Engineering

    1995-05-01

    In this paper, the effects of Cu, Mo, Si contents on the volume fraction of retained austenite of austempered ductile iron (ADI) are analyzed exactly by X-ray diffraction, and the fracture modes of test samples with different volume fraction of retained austenite are investigated by SEM. It is shown that the retained austenite content increases with the content of copper, decreases with the content of molybdenum, and reaches the maximum with a certain content of silicon. When the retained austenite content decreases, the fracture modes of test samples change from ductile fracture to cleavage fracture.

  3. Morphology and constitution of the phases in as-welded microstructure of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.Y.; Zhou, Z.F.; Sun, D.Q.

    2005-06-15

    It was found by optical and electron microscopic examination of the microstructure of as-weld austempered ductile iron that the weld matrix is composed of austenite and bainite, the volume fractions of which were determined. In addition, the carbon content of austenite was measured and therefore the average carbon content of the matrix was calculated. In the matrix of the weld metal two types of bainite, bainite ferrite and lower bainite, were found. According to the morphology and distribution of the bainite plates, the nucleation and growth modes of bainite was inferred. (author)

  4. Effects of matrix structures on fracture mechanisms of austempered ductile cast iron

    Energy Technology Data Exchange (ETDEWEB)

    Doi, Shigeru; Matsufuji, Kenichi [Oita Univ. (Japan); Mitsunaga, Koichi [Kagoshima Junior Womens College (Japan); Takahara, Masao [Isuzu Motors, Kawasaki, Kanagawa (Japan)

    1995-12-31

    On the fatigue behavior of Austempered Ductile Iron (so called ADI), rotating fatigue tests in very high cycle region were performed. The S-N curve represented the double bending. This behavior is caused by the high cycle (>10{sup 7} cycles) fracture, and called the complex three region fractures. The main reason is the work hardening in the surface layer. Therefore, it was removed by electropolishing the surface layer with work hardening. The S-N curve did not show the double bending mentioned above. The fatigue strength with bainitic structure of electropolished ADI was higher than those of mother pearlitic structure.

  5. Behavior Of Austempered Ductile Irons (ADI) Subjected To Laser Surface Melting

    Science.gov (United States)

    Jones, D. L.; Fagoaga, I.; Liceaga, J. F.; Sanz Justes, Pedro; Jasnowski, Kazie S.

    1989-03-01

    The near surface microstructure of 3 austempered ductile irons has been modified using laser surface melting (LSM). A white cast iron layer was produced to depths of up to 500 microns. The microstructure of this region varied depending upon the parameters used. A heat affected zone (HAZ) appeared at an abrupt transition between the LSM zone and the substrate. The size of the HAZ, which varied between 20 and 200 microns was predominately affected by the pass velocity in the range of energies used. The hardness profiles showed large variations in the Haz probably due to varing tempering effects from the subsequent passes.

  6. Mathematical formalisms to represent knowledge concerning the production process of austempered ductile iron

    Directory of Open Access Journals (Sweden)

    D. Wilk-Kołodziejczyk

    2015-10-01

    Full Text Available The aim of this study is to develop computer tools for calculation of the Fe - Fe3C phase equilibrium diagram. The phase equilibrium diagram is of fundamental importance in materials science and heat treatment processes of ferrous alloys. It enables prediction of carbon steel microstructure in the annealed condition, and facilitates selection of proper temperature for the heat treatment process. Choosing the right values of the heat treatment process parameters is essential in the production of Austempered Ductile Iron (ADI.

  7. Embrittlement of austempered nodular irons: Grain boundary phosphorus enrichment resulting from precipitate decomposition

    Science.gov (United States)

    Klug, R. C.; Hintz, M. B.; Rundman, K. B.

    1985-05-01

    The microstructures, mechanical properties, and fracture behavior were characterized for a series of Mg treated nodular cast iron specimens austenitized at 1170, 1255, and 1340 K and subsequently austempered at 640 K. The ductility and toughness of the alloy decreased as austenitization temperatures were increased, which is contrary to the behavior anticipated from the observed micro-structural evolution. Fractographic and surface chemical analyses demonstrated that the mechanical property degradation was associated with embrittlement of the austenite grain boundaries by phosphorus. The primary mechanism of grain boundary phosphorus enrichment does not appear to be equilibrium segregation, and an alternative mechanism based on the decomposition of P rich precipitates is proposed and discussed.

  8. Dwarf spheroidal galaxies keystones of galaxy evolution

    CERN Document Server

    Gallagher, S C; Gallagher, S; Wyse, F G

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  9. Stress Clamp Experiments on Multicellular Tumor Spheroids

    CERN Document Server

    Montel, Fabien; Elgeti, Jens; Malaquin, Laurent; Basan, Markus; Risler, Thomas; Cabane, Bernard; Vignjevic, Danijela; Prost, Jacques; Cappello, Giovanni; Joanny, Jean-François; 10.1103/PhysRevLett.107.188102

    2011-01-01

    The precise role of the microenvironment on tumor growth is poorly understood. Whereas the tumor is in constant competition with the surrounding tissue, little is known about the mechanics of this interaction. Using a novel experimental procedure, we study quantitatively the effect of an applied mechanical stress on the long-term growth of a spheroid cell aggregate. We observe that a stress of 10 kPa is sufficient to drastically reduce growth by inhibition of cell proliferation mainly in the core of the spheroid. We compare the results to a simple numerical model developed to describe the role of mechanics in cancer progression.

  10. Material Characterization of Austempered Ductile Iron (ADI) Produced by a Sustainable Continuous Casting-Heat Treatment Process

    Science.gov (United States)

    Meena, Anil; El Mansori, Mohamed

    2012-12-01

    Selecting a suitable manufacturing process is one way of achieving sustainability of a product by diminishing energy consumption during its production cycle and improving material efficiency. The article attempts to explore the new processing technology for direct manufacturing of lightweight austempered ductile iron (ADI) casting in a permanent mold. The new processing technology is based on the innovative integrated approach toward casting and heat-treatment process. In this technology, the ductile iron samples obtained using the permanent mold are first austenized immediately after solidification process followed by austempering heat treatment in the fluidized bed and then air cooled at room temperature to obtain ADI material. The influence of austempering time on the microstructural characteristics, mechanical properties, and strain-hardening behavior of ADI was studied. Optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses were performed to correlate the mechanical properties with microstructural characteristics. It was observed that the mechanical properties of resulting ADI samples were influenced by the microstructural transformations and varied retained austenite volume fractions obtained due to different austempering time. The results indicate that the strain-hardening behavior of the ADI material is influenced by the carbon content of retained austenite.

  11. Improvement in Abrasion Wear Resistance and Microstructural Changes with Deep Cryogenic Treatment of Austempered Ductile Cast Iron (ADI)

    Science.gov (United States)

    Šolić, Sanja; Godec, Matjaž; Schauperl, Zdravko; Donik, Črtomir

    2016-10-01

    The application of a deep cryogenic treatment during the heat-treatment processes for different types of steels has demonstrated a significant influence on their mechanical and tribological properties. A great deal of research was conducted on steels, as well as on other kinds of materials, such as hard metal, gray cast iron, aluminum, aluminum alloys, etc., but not on austempered ductile iron (ADI). In this research the influence of a deep cryogenic treatment on the microstructure and abrasive wear resistance of austempered ductile iron was investigated. The ductile cast iron was austempered at the upper ausferritic temperature, deep cryogenically treated, and afterwards tempered at two different temperatures. The abrasion wear resistance was tested using the standard ASTM G65 method. The microstructure was characterized using optical microscopy, field-emission scanning electron microscopy, electron back-scattered diffraction, and X-ray diffraction in order to define the microstructural changes that influenced the properties of the ADI. The obtained results show that the deep cryogenic treatment, in combination with different tempering temperatures, affects the matrix microstructure of the austempered ductile iron, which leads to an increase in both the abrasion wear resistance and the hardness.

  12. Nano-scale orientation mapping of graphite in cast irons

    Energy Technology Data Exchange (ETDEWEB)

    Theuwissen, Koenraad; Lacaze, Jacques [Institut CARNOT CIRIMAT, Université de Toulouse, ENSIACET, CS 44362, 31030 Toulouse Cedex 4 (France); Véron, Muriel [SIMAP, CNRS-Grenoble INP, BP 46 101 rue de la Physique, 38402 Saint Martin d' Hères (France); Laffont, Lydia, E-mail: lydia.laffont@ensiacet.fr [Institut CARNOT CIRIMAT, Université de Toulouse, ENSIACET, CS 44362, 31030 Toulouse Cedex 4 (France)

    2014-09-15

    A diametrical section of a graphite spheroid from a ductile iron sample was prepared using the focused ion beam-lift out technique. Characterization of this section was carried out through automated crystal orientation mapping in a transmission electron microscope. This new technique automatically collects electron diffraction patterns and matches them with precalculated templates. The results of this investigation are crystal orientation and phase maps of the specimen, which bring new light to the understanding of growth mechanisms of this peculiar graphite morphology. This article shows that mapping the orientation of carbon-based materials such as graphite, which is difficult to achieve with conventional techniques, can be performed automatically and at high spatial resolution using automated crystal orientation mapping in a transmission electron microscope. - Highlights: • ACOM/TEM can be used to study the crystal orientation of carbon-based materials. • A spheroid is formed by conical sectors radiating from a central nuclei. • Misorientations exist within the conical sectors, defining various orientation domains.

  13. Convection in Slab and Spheroidal Geometries

    Science.gov (United States)

    Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.

    2000-01-01

    Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.

  14. Zero-point energy in spheroidal geometries

    OpenAIRE

    Kitson, A. R.; Signal, A. I.

    2005-01-01

    We study the zero-point energy of a massless scalar field subject to spheroidal boundary conditions. Using the zeta-function method, the zero-point energy is evaluated for small ellipticity. Axially symmetric vector fields are also considered. The results are interpreted within the context of QCD flux tubes and the MIT bag model.

  15. Blue straggler stars in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    Mapelli, M.; Ripamonti, E.; Tolstoy, E.; Sigurdsson, S.; Irwin, M. J.; Battaglia, G.

    2007-01-01

    Blue straggler star (BSS) candidates have been observed in all old dwarf spheroidal galaxies (dSphs), however whether or not they are authentic BSSs or young stars has been a point of debate. To both address this issue and obtain a better understanding of the formation of BSSs in different environme

  16. Convection in Slab and Spheroidal Geometries

    Science.gov (United States)

    Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.

    2000-01-01

    Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.

  17. The studies of mechanical properties and structure of ADI as function of austempering parameters

    Directory of Open Access Journals (Sweden)

    A. Krzyńska

    2010-10-01

    Full Text Available The results of study of ductile iron austempered using different parameters of austempering are presented. The aim of the investigations was to look closer into mechanical properties of this very attractive cast material. The experiment was carried out with commercial EN-GJS-500-7 grade ductile iron. The specimens were first solution heat treated 1 hour in 910oC and then isothermally quenched for different time in molten tin of different temperature. The mechanical properties heat treated specimens were tested using tensile test machine to evaluate Rp,0.2, Rm and A10. Moreover Brinell hardness tests were carried out for structure investigation conventional light microscopy only was used. It was discovered, that low yield strength ADI obtained for short time quenching at 275oC exhibited high strengthening effect while tensile strained. So it was concluded that this had to by cause by large amount of untransformed austenite, which FCC lattice providing large number of glide systems.

  18. 奥氏体等温转变铸铁研究的新进展%Recent Researches on Austempered Cast Irons

    Institute of Scientific and Technical Information of China (English)

    赵红; 徐卫平; 周继扬

    2001-01-01

    Recent researches on austempered cast irons have been reviewed. The present theories of the austempering transformation and the stability of high carbon austenite in ductile cast iron have been presented. The effects of chemical and mechanical deformation on austempering transformation have been discussed. The heat treatment processes, some mechanical properties and their applications of austempered gray iron, austempered compacted iron and austempered malleable iron have been introduced.%综述了奥氏体等温转变铸铁的最新研究成果。阐述了球墨铸铁奥氏体等温转变的最新理论及高碳奥氏体的稳定性,论述了化学成分及形变对奥氏体等温转变过程的影响,概述了奥氏体等温转变灰铸铁、蠕墨铸铁及可锻铸铁的热处理工艺特点、性能及其应用。

  19. A graphite nanoeraser

    DEFF Research Database (Denmark)

    Liu, Ze; Bøggild, Peter; Yang, Jia-rui;

    2011-01-01

    We present here a method for cleaning intermediate-size (up to 50 nm) contamination from highly oriented pyrolytic graphite and graphene. Electron-beam-induced deposition of carbonaceous material on graphene and graphite surfaces inside a scanning electron microscope, which is difficult to remove...... by conventional techniques, can be removed by direct mechanical wiping using a graphite nanoeraser, thus drastically reducing the amount of contamination. We discuss potential applications of this cleaning procedure....

  20. Graphitic Carbons and Biosignatures

    OpenAIRE

    Bernard, S.; Papineau, D

    2014-01-01

    The unambiguous identification of graphitic carbons as remains of life in ancient rocks is challenging because fossilized biogenic molecules are inevitably altered and degraded during diagenesis and metamorphism of the host rocks. Yet, recent studies have highlighted the possible preservation of biosignatures carried by some of the oldest graphitic carbons. Laboratory simulations are increasingly being used to better constrain the transformations of organic molecules into graphitic carbons in...

  1. Oxidation Resistant Graphite Studies

    Energy Technology Data Exchange (ETDEWEB)

    W. Windes; R. Smith

    2014-07-01

    The Very High Temperature Reactor (VHTR) Graphite Research and Development Program is investigating doped nuclear graphite grades exhibiting oxidation resistance. During a oxygen ingress accident the oxidation rates of the high temperature graphite core region would be extremely high resulting in significant structural damage to the core. Reducing the oxidation rate of the graphite core material would reduce the structural effects and keep the core integrity intact during any air-ingress accident. Oxidation testing of graphite doped with oxidation resistant material is being conducted to determine the extent of oxidation rate reduction. Nuclear grade graphite doped with varying levels of Boron-Carbide (B4C) was oxidized in air at nominal 740°C at 10/90% (air/He) and 100% air. The oxidation rates of the boronated and unboronated graphite grade were compared. With increasing boron-carbide content (up to 6 vol%) the oxidation rate was observed to have a 20 fold reduction from unboronated graphite. Visual inspection and uniformity of oxidation across the surface of the specimens were conducted. Future work to determine the remaining mechanical strength as well as graphite grades with SiC doped material are discussed.

  2. Thermodynamic Analysis of Cast Irons Solidification With Various Types of Graphite

    Directory of Open Access Journals (Sweden)

    Elbel T.

    2012-12-01

    Full Text Available The contribution summarises the results of oxygen activity determinations, which were measured and registered continuously in castings from cast irons with various types of graphite. The results were used to find the relationship between two variables: natural logarithm of oxygen activities and reverse value of thermodynamic temperature 1 /T. Obtained regression lines were used to calculate oxygen activity at different temperatures, to calculate Gibbs free energy ΔG at the different temperatures and to calculate the single ΔG value for significant temperature of the graphite solidification. The results were processed by a statistical analysis of data files for the different types of graphite with flake, vermicular and spheroidal graphite. Each material has its proper typical oxygen activities range and individual temperature function of Gibbs free energy for analysing and governing casting quality.

  3. Electron microstructure and mechanical properties of silicon and aluminum ductile irons

    Energy Technology Data Exchange (ETDEWEB)

    Sidjanin, L. (Univ. of Novi Sad (Yugoslavia). Dept. of Production Engineering); Smallman, R.E.; Young, J.M. (Univ. of Birmingham (United Kingdom). School of Metallurgy and Materials)

    1994-09-01

    Samples of unalloyed silicon and aluminum spheroidal graphite cast iron have been studied in the austempered condition. Austempering times of up to 3 h at 400 C for Al SG and 1 h at 350 C for Si SG gives a typical ADI microstructure consisting of carbide-free bainitic ferrite and stable, high carbon enriched, retained austenite. This has an attractive combination of elongation and strength. For longer austempering times transition carbides are precipitated in the bainitic ferrite, [eta]-carbide in the upper bainitic range, i.e. 400 C for Al SG and 350 C for Si SG, and [epsilon]-carbide in the lower bainite range. Increasing amounts of transition carbide reduce the ductility and produce a mixed mode of fracture. For longer austempering times [chi]-carbide is precipitated at the ferrite/austenite boundaries leading to a more brittle fracture mode.

  4. Method for producing dustless graphite spheres from waste graphite fines

    Science.gov (United States)

    Pappano, Peter J [Oak Ridge, TN; Rogers, Michael R [Clinton, TN

    2012-05-08

    A method for producing graphite spheres from graphite fines by charging a quantity of spherical media into a rotatable cylindrical overcoater, charging a quantity of graphite fines into the overcoater thereby forming a first mixture of spherical media and graphite fines, rotating the overcoater at a speed such that the first mixture climbs the wall of the overcoater before rolling back down to the bottom thereby forming a second mixture of spherical media, graphite fines, and graphite spheres, removing the second mixture from the overcoater, sieving the second mixture to separate graphite spheres, charging the first mixture back into the overcoater, charging an additional quantity of graphite fines into the overcoater, adjusting processing parameters like overcoater dimensions, graphite fines charge, overcoater rotation speed, overcoater angle of rotation, and overcoater time of rotation, before repeating the steps until graphite fines are converted to graphite spheres.

  5. Fractomechanical Properties of As-Cast and Austempered SG Cast Iron Between -40 °C and +20 °C

    Directory of Open Access Journals (Sweden)

    V.E. Fierro

    2002-06-01

    Full Text Available The spheroidal graphite (SG cast iron fractomechanical response varies with the test temperature and with the microstructure parameters. In the present paper, we analyze this variation performing fractomechanical tests in a temperature range from -40°C to +20°C, doing also Charpy and tensile tests for material characterization. The tests were carried out on as-cast samples and heat treated samples to obtain an ADI grade 1. In both cases, we studied samples taken from two well differentiated "Y" block sizes. The results obtained show that, for the chemical composition analyzed, both castings have a fractomechanical response decrease as the temperature diminishes. Besides, the block size enlargement produce a deterioration of the mechanical properties (the fracture toughness, mainly, for both castings.

  6. Terahertz generation from graphite

    NARCIS (Netherlands)

    Ramakrishnan, G.; Chakkittakandy, R.; Planken, P.C.M.

    2009-01-01

    Generation of subpicosecond terahertz pulses is observed when graphite surfaces are illuminated with femtosecond near-infrared laser pulses. The nonlinear optical generation of THz pulses from graphite is unexpected since, in principle, the material possesses a centre of inversion symmetry.

  7. Pulsar searches in nearby dwarf spheroidal galaxies

    Science.gov (United States)

    Rubio-Herrera, Eduardo; Maccarone, Thomas

    2013-03-01

    We have been undertaking a comprehensive survey for pulsars and fast radio transients in the dwarf spheroidal satellite galaxies of the Milky Way using the Green Bank Radio Telescope operating at a central frequency of 350 MHz. Our search pipeline allows the detection of periodical signals and single dispersed pulses and it is optimized to search for millisecond radio pulsars. Here we present preliminary results of the searches we have conducted in the Ursa Minoris, Draco and Leo I dwarf spheroidal satellite galaxies. Our searches have revealed no periodic signals but a few unconfirmed millisecond single pulses at various dispersion measures, possibly related to neutron stars. Detecting neutron stars in these systems can potentially help to test the existence of haloes of dark matter surrounding these systems as predicted by Dehnen & King (2006).

  8. Making electromagnetic wavelets: II. Spheroidal shell antennas

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Gerald [Center for Signals and Waves, 3803 Tonkawa Trail 2, Austin, TX (United States)

    2005-01-14

    In the companion paper, a charge-current distribution was obtained for radiating electromagnetic wavelets. However, it cannot be realized because of two drawbacks: (a) it requires the existence of magnetic charges, and (b) the charge-current distribution, which is concentrated on a spheroidal surface S{sub {alpha}}, is too singular for practical implementation. Both of these difficulties are resolved here. The first is resolved by using Hertz vectors to generate a charge-current distribution on S{sub {alpha}} due solely to bound electric charges. The second is resolved by replacing S{sub {alpha}} with a spheroidal shell of finite thickness. This generalizes the usual boundary conditions on an interface between electromagnetic media by allowing the transition to be gradual.

  9. New Classes of Charged Spheroidal Models

    Directory of Open Access Journals (Sweden)

    S. Thirukkanesh

    2013-01-01

    Full Text Available New classes of exact solutions to the Einstein-Maxwell system is found in closed form by assuming that the hypersurface is spheroidal. This is achieved by choosing a particular form for the electric field intensity. A class of solution is found for all positive spheroidal parameter for a specific form of electric field intensity. In general, the condition of pressure isotropy reduces to a difference equation with variable, rational coefficients that can be solved. Consequently, an explicit solution in series form is found. By placing restrictions on the parameters, it is shown that the series terminates and there exist two classes of solutions in terms of elementary functions. These solutions contain the models found previously in the limit of vanishing charge. Solutions found are directly relating the spheroidal parameter and electric field intensity. Masses obtained are consistent with the previously reported experimental and theoretical studies describing strange stars. A physical analysis indicates that these models may be used to describe a charged sphere.

  10. Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury

    OpenAIRE

    Swetha Sara Philip; Deepa John; Sheeja Susan John

    2012-01-01

    Reports of graphite pencil lead injuries to the eye are rare. Although graphite is considered to remain inert in the eye, it has been known to cause severe inflammation and damage to ocular structures. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies following a graphite pencil injury.

  11. Directly spheroidizing during hot deformation in GCr15 steels

    Institute of Scientific and Technical Information of China (English)

    Guo-hui ZHU; Gang ZHENG

    2008-01-01

    The spheroidizing heat treatment is normally required prior to the cold forming in GCr15 steel in order to improve its machinability. In the conventional spher-oidizing process, very long annealing time, generally more than 10 h, is needed to assure proper spheroidizing. It results in low productivity, high cost, and especially high energy consumption. Therefore, the possibility of directly spheroidizing during hot deformation in GCr15 steel is preliminarily explored. The effect of hot deformation parameters on the final microstructure and hardness is investigated systematically in order to develop a directly spheroidizing technology. Experimental results illustrate that low deformation temperature and slow cooling rate is the favorite in directly softening and/or spheroidizing dur-ing hot deformation, which allows the properties of as-rolled GCr15 to be applicable for post-machining without requirement of prior annealing.

  12. In-situ SEM observation on fracture behavior of austempered silicon alloyed steel

    Institute of Scientific and Technical Information of China (English)

    Chen Xiang; Vuorinen Esa; Grahn Jonny

    2009-01-01

    Crack initiation,propagation and microfracture processes of austempered high silicon cast steel have been investigated by using an in-situ tensile stage installed inside a scanning electron microscope chamber. It is revealed that micro cracks always nucleate at the yielding near imperfections and the boundary of matrix-inclusions due to the stress concentration. There are four types of crack propagations in the matrix:crack propagates along the boundary of two clusters of bainitic ferrite;crack propagates along the boundary of ferrite-austenite in bainitic ferrite laths;crack propagates into bainitic ferrite laths;crack nucleates and propagates in the high carbon brittle plate shape martensite which is transformed from some blocky retained austenite due to plastic deformation.Based on the observation and analysis of microfracture processes,a schematic diagram of the crack nucleation and propagation process of high silicon cast steel is proposed.

  13. Numerical Simulation of Austempering Heat Treatment of a Ductile Cast Iron

    Science.gov (United States)

    Boccardo, Adrián D.; Dardati, Patricia M.; Celentano, Diego J.; Godoy, Luis A.; Górny, Marcin; Tyrała, Edward

    2016-02-01

    This paper presents a coupled thermo-mechanical-metallurgical formulation to predict the dimensional changes and microstructure of a ductile cast iron part as a consequence of an austempering heat process. To take into account the different complex phenomena which are present in the process, the stress-strain law and plastic evolution equations are defined within the context of the associate rate-independent thermo-plasticity theory. The metallurgical model considers the reverse eutectoid, ausferritic, and martensitic transformations using macro- and micro-models. The resulting model is solved using the finite element method. The performance of this model is evaluated by comparison with experimental results of a dilatometric test. The results indicate that both the experimental evolution of deformation and temperature are well represented by the numerical model.

  14. Multi-Response Optimization of Carbidic Austempered Ductile Iron Production Parameters using Taguchi Method

    Science.gov (United States)

    Dhanapal, P.; Mohamed Nazirudeen, S. S.; Chandrasekar, A.

    2012-04-01

    Carbide Austempered Ductile Iron (CADI) is the family of ductile iron containing wear resistance alloy carbides in the ausferrite matrix. This CADI is manufactured by selecting and characterizing the proper material composition through the melting route done. In an effort to arrive the optimal production parameters of multi responses, Taguchi method and Grey relational analysis have been applied. To analyze the effect of production parameters on the mechanical properties signal-to-noise ratio and Grey relational grade have been calculated based on the design of experiments. An analysis of variance was calculated to find the amount of contribution of factors on mechanical properties and their significance. The analytical results of Taguchi method were compared with the experimental values, and it shows that both are identical.

  15. Comparing the possibilities of austenite content determination in austempered ductile iron

    Directory of Open Access Journals (Sweden)

    D. Myszka

    2011-07-01

    Full Text Available The article presents various methods for assessment of the austenite volume fraction in Austempered Ductile Iron (ADI. Tests were carried out on two types of ADI, i.e. unalloyed and alloyed with the addition of 0.72%Cu and 0.27%Mo, heat treated under different conditions of isothermal transformation to obtain different austenite volume fractions. The test material was then subjected to metallographic examinations, X-ray diffraction (XRD analysis, an analysis using the author's genuine programme of artificial neural networks, image analysis and magnetic measurements. The results were compared with each other indicating the possibility of a quantitative measurement of austenite and other phases present in cast iron. It was found that different methods of measurement are not fully consistent with each other but show similar results of the austenite content.

  16. In-Situ Studies of Intercritically Austempered Ductile Iron Using Neutron Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Druschitz, Alan [University of Alabama, Birmingham; Aristizabal, Ricardo [University of Alabama, Birmingham; Druschitz, Edward [University of Alabama, Birmingham; Hubbard, Camden R [ORNL; Watkins, Thomas R [ORNL; Walker, Larry R [ORNL; Ostrander, M [Rex Heat Treat, Anniston, AL

    2012-01-01

    Intercritically austempered ductile irons hold promise for applications requiring fatigue durability, excellent castability, low production energy requirements, reduced greenhouse gas emissions and excellent machinability. In the present study, four different ductile iron alloys, containing manganese and nickel as the primary austenite-stabilizing elements, were heat treated to obtain different quantities of austenite in the final microstructure. This paper reports the microstructures and phases present in these alloys. Further, lattice strains and diffraction elastic constants in various crystallographic directions and the transformation characteristics of the austenite as a function of applied stress were determined using in-situ loading with neutron diffraction at the second generation Neutron Residual Stress Facility (NRSF2) at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL).

  17. Microstructure evolution during surface alloying of ductile iron and austempered ductile iron by electron beam melting

    Science.gov (United States)

    Gulzar, A.; Akhter, J. I.; Ahmad, M.; Ali, G.; Mahmood, M.; Ajmal, M.

    2009-07-01

    Alloying and microstructural modification of surfaces by electron beam has become popular to tailor the surface properties of materials. Surface modification of as-received ductile iron, Ni-plated ductile iron and Ni-plated austempered ductile iron was carried out by electron beam melting to improve the surface properties. Martensitic structure evolved in the heat affected zone and ledeburite structure was produced in the molten zone of the ductile iron. Microhardness of the melted specimens enhanced considerably as compared to the as-received samples. However the microhardness of melted Ni-plated samples is lower than that of the unplated specimens. X-ray diffraction clearly revealed the formation of an austenite and Fe 3C phases in the electron beam molten zone. The broadening of peaks suggests refinement of the microstructure as well as internal stresses generated during electron beam melting.

  18. In Situ Studies of Intercritically Austempered Ductile Iron Using Neutron Diffraction

    Science.gov (United States)

    Druschitz, Alan P.; Aristizabal, Ricardo E.; Druschitz, Edward; Hubbard, C. R.; Watkins, Thomas R.; Walker, L.; Ostrander, Mel

    2012-05-01

    Intercritically austempered ductile irons hold promise for applications requiring fatigue durability, excellent castability, low production energy requirements, reduced greenhouse gas emissions, and excellent machinability. In the present study, four different ductile iron alloys, containing manganese and nickel as the primary austenite-stabilizing elements, were heat treated to obtain different quantities of austenite in the final microstructure. This article reports the microstructures and phases present in these alloys. Furthermore, lattice strains and diffraction elastic constants in various crystallographic directions and the transformation characteristics of the austenite were determined as a function of applied stress using in situ loading during neutron diffraction at the second generation Neutron Residual Stress Facility at the High Flux Isotope Reactor at Oak Ridge National Laboratory.

  19. Anti-friction Coating for Drilling of Green Austempered Ductile Iron (ADI) grade

    Science.gov (United States)

    Meena, A.; El Mansori, M.; Ghidossi, P.; Mkaddem, A.

    2011-05-01

    In this paper the anti-friction performance of two types of coating, post-coated coating and PVD-TiAlN coating were investigated when drilling green austempered ductile iron (ADI) grade. The green ADI grade is produced by a new processing technology known as continuous casting-heat treatment process. The effect of coatings on tool wear and surface finish of the holes when drilling using coolant were reported. Results showed that the tool with post-coated coating has higher anti-friction properties as compared to PVD-TiAlN coating in terms of tool wear and surface roughness. Results also showed that there is a formation of preventive aluminum oxide layer during machining for both types of coating.

  20. Fatigue of Austempered Ductile Iron with Two Strength Grades in Very High Cycle Regime

    Science.gov (United States)

    Zhang, Jiwang; Li, Wei; Song, Qingpeng; Zhang, Ning; Lu, Liantao

    2016-03-01

    In this study, Austempered ductile irons (ADIs) with two different strength grades were produced and the fatigue properties were measured at 109 cycles. The results show that the S-N curves give a typical step-wise shape and there is no fatigue limit in the very high cycle fatigue regime. The two grades ADI have the similar fracture behaviors and fatigue failure can initiate from defects at specimen surface and subsurface zone. On the fracture surfaces of some specimens, the `granular-bright-facet' area with rich carbon distribution is observed in the vicinity of the defect. The microstructure affects the crack behaviors at the early propagation stage. The ADI with upper and lower bainite shows higher fatigue strength compared with the ADI with coarse upper bainite.

  1. Transition temperature and fracture mode of as-castand austempered ductile iron.

    Science.gov (United States)

    Rajnovic, D; Eric, O; Sidjanin, L

    2008-12-01

    The ductile to brittle transition temperature is a very important criterion that is used for selection of materials in some applications, especially in low-temperature conditions. For that reason, in this paper transition temperature of as-cast and austempered copper and copper-nickel alloyed ductile iron (DI) in the temperature interval from -196 to +150 degrees C have been investigated. The microstructures of DIs and ADIs were examined by light microscope, whereas the fractured surfaces were observed by scanning electron microscope. The ADI materials have higher impact energies compared with DIs in an as-cast condition. In addition, the transition curves for ADIs are shifted towards lower temperatures. The fracture mode of Dls is influenced by a dominantly pearlitic matrix, exhibiting mostly brittle fracture through all temperatures of testing. By contrast, with decrease of temperature, the fracture mode for ADI materials changes gradually from fully ductile to fully brittle.

  2. Effect of Water on Ductility and Fatigue Strength of Austempered Ductile Cast Iron (adi)

    Science.gov (United States)

    Yakushiji, Terutoshi; Ferguson, W. George; Goto, Masahiro

    In order to study the mechanism of decreasing tensile strength and elongation of Austempered Ductile Cast Iron (ADI) in the wet condition, various tension tests and impact tests were carried out. Three point bending fatigue tests were carried out on ADI and annealed 0.55% carbon steel to clarify the influence of water on fatigue strength. The main conclusions are as follow. Embrittlement by water begins when plastic deformation starts in a tension test. The fatigue limit of ADI in water showed a lower value than that in air. The influence of a water environment on fatigue behaviour was similar to that of annealed 0.55% carbon steel. Embrittlement such as that in a tension test was not observed in a fatigue test.

  3. Determination of the fatigue limit of an austempered ductile iron using thermal infrared imagry

    Science.gov (United States)

    Geraci, Alberto L.; La Rosa, Guido; Risitano, Antonino; Grech, Maurice

    1995-12-01

    Previous work by the authors showed that the endurance limit of specimens, or mechanical components, can be predicted using thermal infrared imagery. The new technique enables the determination of the fatigue strength limit in a comparatively short period of time (few thousands cycles), and using very few specimens (theoretically only 1). The present work applies this technique to rotating-bending test specimens of austempered ductile iron, an alloy whose fatigue limit is, due to the high scatter dispersion of the data points and the long testing period required, generally difficult to determine by the traditional technique. This material exhibited higher fatigue strength than the familiar nodular cast iron. This was confirmed by the results derived from the traditional Wohler test and the new technique, and supported by the data gathered from literature.

  4. Microstructure evolution during surface alloying of ductile iron and austempered ductile iron by electron beam melting

    Energy Technology Data Exchange (ETDEWEB)

    Gulzar, A. [Materials Division, Pakistan Institute of Nuclear Science and Technology, Nilore, Islamabad (Pakistan); Akhter, J.I. [Physics Division, Pakistan Institute of Nuclear Science and Technology, Nilore, Islamabad (Pakistan); Ahmad, M., E-mail: maqomer@yahoo.com [Physics Division, Pakistan Institute of Nuclear Science and Technology, Nilore, Islamabad (Pakistan); Ali, G. [Physics Division, Pakistan Institute of Nuclear Science and Technology, Nilore, Islamabad (Pakistan); Mahmood, M. [Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences, Islamabad (Pakistan); Ajmal, M. [Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore (Pakistan)

    2009-07-30

    Alloying and microstructural modification of surfaces by electron beam has become popular to tailor the surface properties of materials. Surface modification of as-received ductile iron, Ni-plated ductile iron and Ni-plated austempered ductile iron was carried out by electron beam melting to improve the surface properties. Martensitic structure evolved in the heat affected zone and ledeburite structure was produced in the molten zone of the ductile iron. Microhardness of the melted specimens enhanced considerably as compared to the as-received samples. However the microhardness of melted Ni-plated samples is lower than that of the unplated specimens. X-ray diffraction clearly revealed the formation of an austenite and Fe{sub 3}C phases in the electron beam molten zone. The broadening of peaks suggests refinement of the microstructure as well as internal stresses generated during electron beam melting.

  5. Austempered Ductile Iron Manufacturing Data Acquisition Process with the Use of Semantic Techniques

    Directory of Open Access Journals (Sweden)

    Wilk-Kołodziejczyk D.

    2016-12-01

    Full Text Available The aim of this work was to propose a methodology supporting the task of collecting the comparative data on studies of the mechanical properties of ADI. Collecting of research data is an important step in the process of finding the optimum design solutions for newly made products - experimental data allow us properly calibrate the manufacturing process of ADI to let the final product achieve the required properties. Parameters of the ADI production process, i.e. the time and temperature of austenitising and austempering, as well as the alloying elements added to ductile iron affect the ADI properties. The design process can use research data collected, among others, from the Web. As stated in the article, the process of data acquisition can be supported by semantic technologies, including ontologies which are descriptive logic formalism.

  6. Effect of initial microstructure on the activation energy of second stage during austempering of ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Campos-Cambranis, R.E.; Narvaez Hernandez, L. [UASLP, San Luis Potosi (Mexico). Instituto de Metalurgia; Cisneros-Guerrero, M.M. [Inst. Tecnologico de Saltillo (Mexico). Dept. Metal-Mecanica; Perez-Lopez, M.J. [Inst. Tecnologico de Zacatecas (Mexico)

    1998-03-13

    The good balance among mechanical properties of austempered ductile irons (ADI) mainly depends on the matrix microstructure, which basically consists of acicular ferrite and carbon-enriched austenite. This structure is produced by isothermal transformation of the austenite over the temperature range of 523 to 673 K. It is well accepted that during the isothermal holding, the transformation takes place in two stages. In the first stage, the austenite decomposes into acicular ferrite and carbon-enriched austenite. When the austenite is transformed at temperatures higher than 623 K, the acicular ferrite is free of carbides; at temperatures below 623 K, besides the formation of the acicular ferrite and austenite, precipitation of carbides takes place over the plates of the acicular ferrite. The mixture of ferrite and austenite is known as ausferrite being the responsible for the good mechanical properties of ADI. In this work, the ausferrite obtained above and below 623 K will be termed high and low temperature ausferrite respectively. Although ausferrite does not transform at room temperature, it is not a thermodynamically stable structure. Consequently, if the isothermal holding is extended, or if ADI is heated at high temperatures (523 to 800 K), the second stage of the austempering reaction will occur. During this stage, the carbon rich austenite will decompose into ferrite and carbides. In order to establish the maximum working temperature of ADI, it is necessary to characterize the thermal stability of ausferrite microstructure, since once stage II takes place, the mechanical properties, in particular ductility and toughness, are adversely affected. In the present work the influence of previous ausferrite microstructure (that obtained during first stage) of an alloyed ductile iron (0.6%Ni, 0.15%Mo) on the empirical activation energy of stage II is studied.

  7. Orbits in Homogeneous Oblate Spheroidal Gravitational Space-Time

    Directory of Open Access Journals (Sweden)

    Chifu E. N.

    2009-07-01

    Full Text Available The generalized Lagrangian in general relativistic homogeneous oblate spheroidal gravitational fields is constructed and used to study orbits exterior to homogenous oblate spheroids. Expressions for the conservation of energy and angular momentum for this gravitational field are obtained. The planetary equation of motion and the equation of motion of a photon in the vicinity of an oblate spheroid are derived. These equations have additional terms not found in Schwarzschild's space time.

  8. The effect of manganese on the onset of the stage 2 reaction in an austempered ductile iron matrix

    Energy Technology Data Exchange (ETDEWEB)

    Hagen, K. N.

    1990-02-01

    Austempered ductile irons (ADIs) possess a unique combination of toughness and ductility plus high strength which make them attractive alternatives to other metal castings. ADIs can have tensile strengths up to 230 ksi with a 1% elongation and high hardness for wear resistant applications, or tensile strengths of approximately 150 ksi and elongations of 14% where a large amount of ductility is required. Austempering is a two step process: complete transformation to the austenite ({gamma}) phase; and a quench and hold in the temperature range of 270--420{degree}C for some time followed by cooling to room temperature. This quench must be sufficiently rapid to avoid formation of pearlite or ferrite if the best mechanical properties are to be obtained. This thesis presents the results of a number of experiments aimed at determining the effect of Mn on the length of the Stage 1 reaction. (austenite decomposes into bainitie ferrite and high carbon austenite). A basic knowledge of the effects of Mn will yield a more complete understanding of the austempering process for the normal case and also when microsegregation is present. The onset time for Stage 2 (high carbon austenite decomposes into bainitic ferrite plus carbides) in ductile irons is a critical parameter because of the associated degradation of the mechanical properties which result from carbide formation.

  9. Effect of austempering process on microstructure and wear behavior of ductile iron containing Mn-Ni-Cu-Mo

    Science.gov (United States)

    PourAsiabi, HaMiD; Saghafian, Hasan; Pourasiabi, Hamed

    2013-01-01

    In this work, the effects of austempering time and temperature on the microstructure and sliding wear behavior of a Mn-Ni-Cu-Mo alloyed ductile iron were investigated. Ductile iron samples with the desired chemical composition were cast according to ASTM A897M-1990 Y-block. Wear test samples austenitized at 900 °C for 90 min, were austempered at 260, 290 and 320 °C for 30, 60, 90 and 120 min. The wear tests on samples were conducted by Block-on-Ring testing machine according to ASTM G77-98 standard, at the applied load of 75N and the displacement speed of 3.27 m/s. The results showed that the sample austempered at 260 °C for 90 min exhibited the maximum relative wear resistance in comparison with the as-cast sample. The X-ray diffraction patterns of wear debris and the SEM observations of worn surfaces and crosssection of worn surfaces together with wear debris showed that delamination associated with oxidation is the dominant wear mechanism in the samples.

  10. Graphite Technology Development Plan

    Energy Technology Data Exchange (ETDEWEB)

    W. Windes; T. Burchell; R. Bratton

    2007-09-01

    This technology development plan is designed to provide a clear understanding of the research and development direction necessary for the qualification of nuclear grade graphite for use within the Next Generation Nuclear Plant (NGNP) reactor. The NGNP will be a helium gas cooled Very High Temperature Reactor (VHTR) with a large graphite core. Graphite physically contains the fuel and comprises the majority of the core volume. Considerable effort will be required to ensure that the graphite performance is not compromised during operation. Based upon the perceived requirements the major data needs are outlined and justified from the perspective of reactor design, reatcor performance, or the reactor safety case. The path forward for technology development can then be easily determined for each data need. How the data will be obtained and the inter-relationships between the experimental and modeling activities will define the technology development for graphite R&D. Finally, the variables affecting this R&D program are discussed from a general perspective. Factors that can significantly affect the R&D program such as funding, schedules, available resources, multiple reactor designs, and graphite acquisition are analyzed.

  11. Efecto del conteo de nódulos en la resistencia al desgaste por abrasión de los hierros dúctiles austemperados. // Effect of nodules count in the waste by abrasion resistance for ductile austempering irons.

    Directory of Open Access Journals (Sweden)

    C. J. Diez Cicero

    2004-05-01

    Full Text Available Entre los materiales metálicos de mayor demanda, la producción de hierro con grafito nodular, ocupa en la actualidad unode los lugares más importantes entre los hierros fundidos de alta resistencia, y con la introducción del tratamiento térmicode austemperado aplicado a estas fundiciones, se da lugar a una nueva familia de materiales, caracterizados por su altaresistencia mecánica y elevada tenacidad, que mantienen la economía y facilidad de producción de las fundicionesnodulares.Este trabajo, hace una valoración del comportamiento de hierros nodulares, con diferentes conteos de nódulos, a los que lesfue aplicado el tratamiento de austemperado y posteriormente se les sometió a ensayos de desgaste abrasivo.Con los resultados obtenidos se hace un análisis de la influencia del conteo de nódulos en dichas propiedades, así comotambién de la interrelación del conteo de nódulos con las variables de tratamiento térmico utilizadas en las muestrasensayadas.Palabras claves: Hierro nodular, conteo de nódulos, austemperado.____________________________________________________________________________Abstract.Between the metallic materials of greater demand, the iron production with nódular graphite occupies at the present time,one of the most important places between fused irons of high resistance, and with the introduction of the austempering heattreatment, applied to these meltings, brings a new family of materials, characterized by its high mechanical resistance andelevated tenacity, that maintain the economy and facility of production of the nodular smeltings.This work makes a valuation of the nodular irons behaviors, with different counts from nodules, to which the austemperingtreatment was applied, and later they were put under tests of abrasive wearing.Of the obtained results, takes control of the influence the nodules count in these properties, as well as, of the interrelation ofthe nodules count, with the used variables of heat

  12. Attenuation of microwaves by poly-disperse small spheroid particles

    Science.gov (United States)

    Zhang, Peichang; Wang, Zhenhui

    1998-08-01

    Expressions for calculating the attenuation cross sections of poly-disperse, small spheroids, whose rotatory axes are in specific status, have been derived from a universal formula for calculating the attenuation cross section of a particle of arbitrary shape. Attenuation cross sections of liquid, ice, and spongy spheroidal droplets in different size and eccentricity at different wave lengths have been computed and analyzed.

  13. Digital microfluidics for automated hanging drop cell spheroid culture.

    Science.gov (United States)

    Aijian, Andrew P; Garrell, Robin L

    2015-06-01

    Cell spheroids are multicellular aggregates, grown in vitro, that mimic the three-dimensional morphology of physiological tissues. Although there are numerous benefits to using spheroids in cell-based assays, the adoption of spheroids in routine biomedical research has been limited, in part, by the tedious workflow associated with spheroid formation and analysis. Here we describe a digital microfluidic platform that has been developed to automate liquid-handling protocols for the formation, maintenance, and analysis of multicellular spheroids in hanging drop culture. We show that droplets of liquid can be added to and extracted from through-holes, or "wells," and fabricated in the bottom plate of a digital microfluidic device, enabling the formation and assaying of hanging drops. Using this digital microfluidic platform, spheroids of mouse mesenchymal stem cells were formed and maintained in situ for 72 h, exhibiting good viability (>90%) and size uniformity (% coefficient of variation screen was performed on human colorectal adenocarcinoma spheroids to demonstrate the ability to recapitulate physiologically relevant phenomena such as insulin-induced drug resistance. With automatable and flexible liquid handling, and a wide range of in situ sample preparation and analysis capabilities, the digital microfluidic platform provides a viable tool for automating cell spheroid culture and analysis.

  14. Engineering analysis and development of the spheroid reservoir bioartificial liver.

    Science.gov (United States)

    McIntosh, Malcolm B; Corner, Stephen M; Amiot, Bruce P; Nyberg, Scott L

    2009-01-01

    A significant demand exists for a liver support device such as a Bioartifical Liver (BAL) to treat patients experiencing acute liver failure. This descriptive paper outlines the design and development of two of the key components of the Mayo Spheroid Reservoir Bioartificial Liver (SRBAL) system. One of the components is the multifunctional Spheroid Reservoir and the other is Multi-shelf Rocker. The Spheroid Reservoir provides an environment to support the viability and functionality of the hepatocyte spheroids at very high cell densities. The Spheroid Reservoir is the biologically active component of this extracorporeal liver support device. Since the Spheroid Reservoir is designed to support 200-400 grams of hepatocyte spheroids, a method to quickly produce large quantities of spheroids is required. The Multi-Shelf Rocker fulfills the production requirement by allowing the culturing of up to six liters of hepatocyte suspension in a conventional laboratory incubator. The SRBAL is designed to provide life sustaining liver-like function to patients in acute liver failure.

  15. Stability of retained austenite in multi-phase microstructure during austempering and its effect on the ductility of a low carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z.J.; Ren, Y.Q.; Zhou, W.H. [School of Materials Science and Engineering, University of Science and Technology, Beijing (China); Yang, J.R. [Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan (China); Shang, C.J., E-mail: cjshang@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology, Beijing (China); Misra, R.D.K. [Laboratory for Excellence in Advanced Steel Research, Center for Structural and Functional Materials, Institute for Material Research and Innovation, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70503 (United States)

    2014-05-01

    The contribution of multi-phase microstructure and retained austenite on mechanical properties of austempered and intercritical annealed Fe–0.23C–1.8Mn–1.35Si (wt%) steel was studied. The multi-phase microstructure comprised of intercritical ferrite (IF), bainite/martensite, and retained austenite. During austempering, the retained austenite was stabilized, which was studied using a combination of experimental (XRD, TEM) and thermodynamic analysis. The termination of bainitic transformation combined with carbon rejection into residual austenite during the second step austempering treatment is believed to be the underlying basis for stabilization of retained austenite. This led to significant increase in uniform and total elongation (25% and 36%, respectively) and the product of tensile strength and % elongation was 33 GPa%. The work hardening behavior of retained austenite exhibited a three-stage process such that necking was delayed. The increased work hardening rate is attributed to the multi-phase microstructure and TRIP effect.

  16. Leukoencephalopathy with spheroids (HDLS) and pigmentary leukodystrophy (POLD)

    Science.gov (United States)

    Wider, C; Van Gerpen, J A.; DeArmond, S; Shuster, E A.; Dickson, D W.; Wszolek, Z K.

    2009-01-01

    Hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) and familial pigmentary orthochromatic leukodystrophy (POLD) present as adult-onset dementia with motor impairment and epilepsy. They are regarded as distinct diseases. We review data from the literature that support their being a single entity. Apart from a slightly older age at onset, a more rapid course, and more prominent pyramidal tract involvement, familial POLD is clinically similar to HDLS. Moreover, the pathologic hallmarks of the two diseases, axonal spheroids in HDLS and pigmented macrophages in POLD, can be identified in both conditions. This supports HDLS and POLD being referred collectively as adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP). GLOSSARY ALSP = adult-onset leukoencephalopathy with axonal spheroids and pigmented glia; HDLS = hereditary diffuse leukoencephalopathy with axonal spheroids; OLD = orthochromatic leukodystrophy; POLD = pigmentary orthochromatic leukodystrophy. PMID:19487654

  17. Design of a Uranium Dioxide Spheroidization System

    Science.gov (United States)

    Cavender, Daniel P.; Mireles, Omar R.; Frendi, Abdelkader

    2013-01-01

    The plasma spheroidization system (PSS) is the first process in the development of tungsten-uranium dioxide (W-UO2) fuel cermets. The PSS process improves particle spherocity and surface morphology for coating by chemical vapor deposition (CVD) process. Angular fully dense particles melt in an argon-hydrogen plasma jet at between 32-36 kW, and become spherical due to surface tension. Surrogate CeO2 powder was used in place of UO2 for system and process parameter development. Particles range in size from 100 - 50 microns in diameter. Student s t-test and hypothesis testing of two proportions statistical methods were applied to characterize and compare the spherocity of pre and post process powders. Particle spherocity was determined by irregularity parameter. Processed powders show great than 800% increase in the number of spherical particles over the stock powder with the mean spherocity only mildly improved. It is recommended that powders be processed two-three times in order to reach the desired spherocity, and that process parameters be optimized for a more narrow particles size range. Keywords: spherocity, spheroidization, plasma, uranium-dioxide, cermet, nuclear, propulsion

  18. Recompressed exfoliated graphite articles

    Science.gov (United States)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2013-08-06

    This invention provides an electrically conductive, less anisotropic, recompressed exfoliated graphite article comprising a mixture of (a) expanded or exfoliated graphite flakes; and (b) particles of non-expandable graphite or carbon, wherein the non-expandable graphite or carbon particles are in the amount of between about 3% and about 70% by weight based on the total weight of the particles and the expanded graphite flakes combined; wherein the mixture is compressed to form the article having an apparent bulk density of from about 0.1 g/cm.sup.3 to about 2.0 g/cm.sup.3. The article exhibits a thickness-direction conductivity typically greater than 50 S/cm, more typically greater than 100 S/cm, and most typically greater than 200 S/cm. The article, when used in a thin foil or sheet form, can be a useful component in a sheet molding compound plate used as a fuel cell separator or flow field plate. The article may also be used as a current collector for a battery, supercapacitor, or any other electrochemical cell.

  19. THE THREE-DIMENSIONAL FUNDAMENTAL SOLUTION TO STOKES FLOW IN THE OBLATE SPHEROIDAL COORDINATES WITH APPLICATIONS TO MULTIPLES SPHEROID PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    庄宏; 严宗毅; 吴望一

    2002-01-01

    A new three-dimensional fundamental solution to the Stokes flow was proposedby transforming the solid harmonic functions in Lamb' s solution into expressions in terms ofthe oblate spheroidal coordinates. These fundamental solutions are advantageous in treatingflows past an arbitrary number of arbitrarily positioned and oriented oblate spheroids. Theleast squares technique was adopted herein so that the convergence difficulties oftenencountered in solving three-dimensional problems were completely avoided. The examplesdemonstrate that present approach is highly accurate, consistently stable andcomputationally efficient.The oblate spheroid may be used to model a variety of particle shapes between acircular disk and a sphere. For the first time, the effect of various geometric factors on theforces and torques exerted on two oblate spheroids were systematically studied by using theproposed fundamental solutions. The generality of this approach was illustrated by twoproblems of three spheroids.

  20. Cesium diffusion in graphite

    Energy Technology Data Exchange (ETDEWEB)

    Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

    1980-05-01

    Experiments on diffusion of /sup 137/Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of /sup 137/Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000/sup 0/C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ..delta..E of the equation D/epsilon = (D/epsilon)/sub 0/ exp (-..delta..E/RT) are about 4 x 10/sup -2/ cm/sup 2//s and 30 kcal/mole, respectively.

  1. Irradiation Creep in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

    An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

  2. Lithium-Graphite Secondary Battery.

    Science.gov (United States)

    1976-12-01

    Used in the experiment that studied the effect of operating current. 6. Li/LiClO 4, PC (0.9M)/Graphite + Graphite glue on carbon cloth. 7. Li/ LiBF4 ...DMSU (1.0M)/Graphite + Graphite glue on carbon cloth. 8. Li/ LiBF4 , PC (1.5M)/Graphite + Graphite glue on carbon cloth. 9. Li/LiClO4, DMSU (2.1M)/Pt. 10... LiBF4 , PC(1.5 M)/Graphite + Graphite glue on carbon cloth. Cycles 1 and 2 51 24. Same as 23. Cycle no. 3, 1-6.3 mA, Q n=2.17 mEq 52 25. Typical

  3. Differentiation of human mesenchymal stem cell spheroids under microgravity conditions

    Directory of Open Access Journals (Sweden)

    Cerwinka Wolfgang H

    2012-06-01

    Full Text Available Abstract To develop and characterize a novel cell culture method for the generation of undifferentiated and differentiated human mesenchymal stem cell 3D structures, we utilized the RWV system with a gelatin-based scaffold. 3 × 106 cells generated homogeneous spheroids and maximum spheroid loading was accomplished after 3 days of culture. Spheroids cultured in undifferentiated spheroids of 3 and 10 days retained expression of CD44, without expression of differentiation markers. Spheroids cultured in adipogenic and osteogenic differentiation media exhibited oil red O staining and von Kossa staining, respectively. Further characterization of osteogenic lineage, showed that 10 day spheroids exhibited stronger calcification than any other experimental group corresponding with significant expression of vitamin D receptor, alkaline phosphatase, and ERp60 . In conclusion this study describes a novel RWV culture method that allowed efficacious engineering of undifferentiated human mesenchymal stem cell spheroids and rapid osteogenic differentiation. The use of gelatin scaffolds holds promise to design implantable stem cell tissue of various sizes and shapes for future regenerative treatment.

  4. Numerical Simulation of Microstructure Formation and Forecast of Mechanical Properties for Spheroidal Graphite Iron

    Institute of Scientific and Technical Information of China (English)

    Weimin ZHAO; Shuping HOU; Haipeng LI; Aiwen HU

    2003-01-01

    The numerical simulation can overcome the hardship of mathematical analysis and experimental research, explicate the mechanism of microstructure shaping, predict mechanical properties and operating life of castings and then optimize technology and control

  5. Graphite-based photovoltaic cells

    Science.gov (United States)

    Lagally, Max; Liu, Feng

    2010-12-28

    The present invention uses lithographically patterned graphite stacks as the basic building elements of an efficient and economical photovoltaic cell. The basic design of the graphite-based photovoltaic cells includes a plurality of spatially separated graphite stacks, each comprising a plurality of vertically stacked, semiconducting graphene sheets (carbon nanoribbons) bridging electrically conductive contacts.

  6. Are z>2 Herschel galaxies proto-spheroids?

    CERN Document Server

    Pozzi, F; Gruppioni, C; Granato, G L; Cresci, G; Silva, L; Pozzetti, L; Matteucci, F; Zamorani, G

    2015-01-01

    We present a backward approach for the interpretation of the evolution of the near-infrared and the far-infrared luminosity functions across the redshift range 02 can be explained as progenitors of local spheroids caught during their formation. We also test the effects of mass downsizing by dividing the spheroids into three populations of different present-day stellar masses. The results obtained in this case confirm the validity of our approach, i.e. that the bulk of proto-spheroids can be modelled by means of a single model which describes the evolution of galaxies at the break of the present-day early type K-band LF.

  7. Modeling a spheroidal microswimmer and cooperative swimming in thin films

    CERN Document Server

    Theers, Mario; Gompper, Gerhard; Winkler, Roland G

    2016-01-01

    We propose a hydrodynamic model for a spheroidal microswimmer with two tangential surface velocity modes. This model is analytically solvable and reduces to Lighthill's and Blake's spherical squirmer model in the limit of equal major and minor semi-axes. Furthermore, we present an implementation of such a spheroidal squirmer by means of multiparticle collision dynamics simulations. We investigate its properties as well as the scattering of two spheroidal squirmers in a slit geometry. Thereby we find a stable fixed point, where two pullers swim cooperatively forming a wedge-like conformation with a small constant angle.

  8. The Strain-Hardening Behavior of Partially Austenitized and the Austempered Ductile Irons with Dual Matrix Structures

    Science.gov (United States)

    Kilicli, Volkan; Erdogan, Mehmet

    2008-04-01

    In the current study, an unalloyed ductile iron containing 3.50 C wt.%, 2.63 Si wt.%, 0.318 Mn wt.%, and 0.047 Mg wt.% was intercritically austenitized (partially austenitized) in two-phase regions (α + γ) at different temperatures for 20 min and then was quenched into salt bath held at austempering temperature of 365 °C for various times to obtain different ausferrite plus proeutectoid ferrite volume fractions. Fine and coarse dual matrix structures (DMS) were obtained from two different starting conditions. Some specimens were also conventionally austempered from 900 °C for comparison. The results showed that a structure having proeutectoid ferrite plus ausferrite (bainitic ferrite + high-carbon austenite (retained or stabilized austenite)) has been developed. Both of the specimens with ˜75% ausferrite volume fraction (coarse structure) and the specimen with ˜82% ausferrite volume fraction (fine structure) exhibited the best combination of high strength and ductility compared to the pearlitic grades, but their ductility is slightly lower than the ferritic grades. These materials also satisfy the requirements for the strength of the quenched and tempered grades and their ductility is superior to this grade. The correlation between the strain-hardening rates of the various austempered ductile iron (ADI) with DMS and conventionally heat-treated ADI microstructures as a function of strain was conducted by inspection of the respective tensile curves. For this purpose, the Crussard-Jaoul (C-J) analysis was employed. The test results also indicate that strain-hardening behavior of ADI with dual matrix is influenced by the variations in the volume fractions of the phases, and their morphologies, the degree of ausferrite connectivity and the interaction intensities between the carbon atoms and the dislocations in the matrix. The ADI with DMS generally exhibited low strain-hardening rates compared to the conventionally ADI.

  9. (Irradiation creep of graphite)

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, C.R.

    1990-12-21

    The traveler attended the Conference, International Symposium on Carbon, to present an invited paper, Irradiation Creep of Graphite,'' and chair one of the technical sessions. There were many papers of particular interest to ORNL and HTGR technology presented by the Japanese since they do not have a particular technology embargo and are quite open in describing their work and results. In particular, a paper describing the failure of Minor's law to predict the fatigue life of graphite was presented. Although the conference had an international flavor, it was dominated by the Japanese. This was primarily a result of geography; however, the work presented by the Japanese illustrated an internal program that is very comprehensive. This conference, a result of this program, was better than all other carbon conferences attended by the traveler. This conference emphasizes the need for US participation in international conferences in order to stay abreast of the rapidly expanding HTGR and graphite technology throughout the world. The United States is no longer a leader in some emerging technologies. The traveler was surprised by the Japanese position in their HTGR development. Their reactor is licensed and the major problem in their graphite program is how to eliminate it with the least perturbation now that most of the work has been done.

  10. Graphite technology development plan

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1986-07-01

    This document presents the plan for the graphite technology development required to support the design of the 350 MW(t) Modular HTGR within the US National Gas-Cooled Reactor Program. Besides descriptions of the required technology development, cost estimates, and schedules, the plan also includes the associated design functions and design requirements.

  11. Magnetic frustration of graphite oxide

    Science.gov (United States)

    Lee, Dongwook; Seo, Jiwon

    2017-01-01

    Delocalized π electrons in aromatic ring structures generally induce diamagnetism. In graphite oxide, however, π electrons develop ferromagnetism due to the unique structure of the material. The π electrons are only mobile in the graphitic regions of graphite oxide, which are dispersed and surrounded by sp3-hybridized carbon atoms. The spin-glass behavior of graphite oxide is corroborated by the frequency dependence of its AC susceptibility. The magnetic susceptibility data exhibit a negative Curie temperature, field irreversibility, and slow relaxation. The overall results indicate that magnetic moments in graphite oxide slowly interact and develop magnetic frustration. PMID:28327606

  12. Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

    Directory of Open Access Journals (Sweden)

    Quanshun Luo

    2017-07-01

    Full Text Available Ultrahigh strength steel 56NiCrMoV7 was austempered at 270 °C for different durations in order to investigate the microstructure evolution, carbon partitioning behaviour and hardness property. Detailed microstructure has been characterised using optical microscopy and field emission gun scanning electron microscopy. A newly developed X-ray diffraction method has been employed to dissolve the bainitic/martensitic ferrite phase as two sub-phases of different tetragonal ratios, which provides quantitative analyses of the carbon partitioning between the resultant ferrites and the retained austenite. The results show that, a short-term austempering treatment was in the incubation period of the bainite transformation, which resulted in maximum hardness being equivalent to the oil-quenching treatment. The associated microstructure comprises fine carbide-free martensitic and bainitic ferrites of supersaturated carbon contents as well as carbon-rich retained austenite. In particular, the short-term austempering treatment helped prevent the formation of lengthy martensitic laths as those being found in the microstructure of oil-quenched sample. When the austempering time was increased from 20 to 80 min, progressive decrease of the hardness was associated with the evolution of the microstructure, including progressive coarsening of bainitic ferrite, carbide precipitating inside high-carbon bainitic ferrite and its subsequent decarbonisation.

  13. 关于奥贝球铁及其微观组织术语的探讨—对ADI(AustemperedDuctileIron)我们需要一个正确的中文术语%Discussion on the Term of Austempered Ductile Iron and Its Microstructure - We need a correct Chinese term for the " austempered ductile iron"

    Institute of Scientific and Technical Information of China (English)

    刘金城

    2002-01-01

    论述了等温淬火球铁的工艺及其微观组织.分析了其微观组织与钢中贝氏体的区别.指出ADI(AustemperedDuctileIron)奥贝球铁是一个不恰当的术语.对这种新铸铁,我们需要一个正确的中文术语:奥铁球铁或者称奥氏体等温淬火球铁.

  14. Delivery of Human Adipose Stem Cells Spheroids into Lockyballs

    Science.gov (United States)

    Pereira, Frederico D. A. S.; Gruber, Peter; Stuart, Mellannie P.; Ovsianikov, Aleksandr; Brakke, Ken; Kasyanov, Vladimir; da Silva, Jorge V. L.; Granjeiro, José M.; Mironov, Vladimir

    2016-01-01

    Adipose stem cells (ASCs) spheroids show enhanced regenerative effects compared to single cells. Also, spheroids have been recently introduced as building blocks in directed self-assembly strategy. Recent efforts aim to improve long-term cell retention and integration by the use of microencapsulation delivery systems that can rapidly integrate in the implantation site. Interlockable solid synthetic microscaffolds, so called lockyballs, were recently designed with hooks and loops to enhance cell retention and integration at the implantation site as well as to support spheroids aggregation after transplantation. Here we present an efficient methodology for human ASCs spheroids biofabrication and lockyballs cellularization using micro-molded non-adhesive agarose hydrogel. Lockyballs were produced using two-photon polymerization with an estimated mechanical strength. The Young’s modulus was calculated at level 0.1362 +/-0.009 MPa. Interlocking in vitro test demonstrates high level of loading induced interlockability of fabricated lockyballs. Diameter measurements and elongation coefficient calculation revealed that human ASCs spheroids biofabricated in resections of micro-molded non-adhesive hydrogel had a more regular size distribution and shape than spheroids biofabricated in hanging drops. Cellularization of lockyballs using human ASCs spheroids did not alter the level of cells viability (p › 0,999) and gene fold expression for SOX-9 and RUNX2 (p › 0,195). The biofabrication of ASCs spheroids into lockyballs represents an innovative strategy in regenerative medicine, which combines solid scaffold-based and directed self-assembly approaches, fostering opportunities for rapid in situ biofabrication of 3D building-blocks. PMID:27829016

  15. Diversity of cell-mediated adhesions in breast cancer spheroids.

    Science.gov (United States)

    Ivascu, Andrea; Kubbies, Manfred

    2007-12-01

    Due to their three dimensional (3D) architecture, multicellular tumor spheroids mimic avascular tumor areas comprising the establishment of diffusion gradients, reduced proliferation rates and increased drug resistance. We have shown recently that the spontaneous formation of spheroids is restricted to a limited number of cell lines whereas the majority grow only as aggregates of cells with loose cell-cell contacts when cultured in 3D. However, by the addition of reconstituted basement membrane (rBM, Matrigel), aggregates can be transformed into spheroids with diffusion barriers and development of quiescent therapy-resistant cells. In this report, we investigated adhesion molecules responsible for rBM-driven versus spontaneous spheroid formation in a diverse population of eight breast tumor cell lines relevant for in vitro and in vivo antitumor drug testing. Inhibition of spheroid formation was monitored in the presence of adhesion molecule functional blocking antibodies and after siRNA-mediated down-regulation of E- and N-cadherin and integrin beta1 adhesion receptors. We identified that E-cadherin mediates the spontaneous formation of spheroids in MCF7, BT-474, T-47D and MDA-MB-361 cells, whereas N-cadherin is responsible for tight packing of MDA-MB-435S cells. In contrast, the matrix protein-induced transformation of 3D aggregates into spheroids in MDA-MB-231 and SK-BR-3 cells is mediated primarily by the collagen I/integrin beta1 interaction with no cadherin involvement. A combination of both, homophilic E-cadherin and integrin beta1/collagen I interaction establishes spheroids in MDA-MB-468 cells. These findings indicate that an evolutionary diverse and complex pattern of interacting cell surface proteins exists in breast cancer cells that determines the 3D growth characteristic in vitro, thereby influencing small molecule or antibody permeation in preclinical in vitro and in vivo tumor models.

  16. New static spheroidal solution in Jordan-Brands-Dicke theory

    CERN Document Server

    Kozyrev, S M

    2010-01-01

    The static spheroidal solutions of Jordan-Brands-Dicke theory (JBD) are studied. We consider the effect of the anisotropic stresses of scalar field on the shape of JBD self-graviting objects. It is shown that scalar fields can have significant effect on the structure and properties of self-graviting objects. In contrast with general relativity in JBD theory there are nonflat static spheroidal solutions.

  17. Wave Dark Matter and Dwarf Spheroidal Galaxies

    Science.gov (United States)

    Parry, Alan R.

    We explore a model of dark matter called wave dark matter (also known as scalar field dark matter and boson stars) which has recently been motivated by a new geometric perspective by Bray. Wave dark matter describes dark matter as a scalar field which satisfies the Einstein-Klein-Gordon equations. These equations rely on a fundamental constant Upsilon (also known as the "mass term'' of the Klein-Gordon equation). Specifically, in this dissertation, we study spherically symmetric wave dark matter and compare these results with observations of dwarf spheroidal galaxies as a first attempt to compare the implications of the theory of wave dark matter with actual observations of dark matter. This includes finding a first estimate of the fundamental constant Upsilon. In the introductory Chapter 1, we present some preliminary background material to define and motivate the study of wave dark matter and describe some of the properties of dwarf spheroidal galaxies. In Chapter 2, we present several different ways of describing a spherically symmetric spacetime and the resulting metrics. We then focus our discussion on an especially useful form of the metric of a spherically symmetric spacetime in polar-areal coordinates and its properties. In particular, we show how the metric component functions chosen are extremely compatible with notions in Newtonian mechanics. We also show the monotonicity of the Hawking mass in these coordinates. Finally, we discuss how these coordinates and the metric can be used to solve the spherically symmetric Einstein-Klein-Gordon equations. In Chapter 3, we explore spherically symmetric solutions to the Einstein-Klein-Gordon equations, the defining equations of wave dark matter, where the scalar field is of the form f(t, r) = eiotF(r) for some constant o ∈ R and complex-valued function F(r). We show that the corresponding metric is static if and only if F( r) = h(r)eia for some constant alpha ∈ R and real-valued function h(r). We describe the

  18. Influence of the amount and morphology of retained austenite on the mechanical properties of an austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Aranzabal, J. [INASMET, San Sebastian (Spain); Gutierrez, I.; Rodriguez-Ibabe, J.M.; Urcola, J.J. [CEIT, San Sebastian (Spain). Dept. of Materials

    1997-05-01

    High Si contents in nodular cast irons lead to a significant volume fraction of retained austenite in the material after the austempering treatment. In the present work, the influence of the amount and morphology of this phase on the mechanical properties (proof stress, ultimate tensile strength (UTS), elongation, and toughness) has been analyzed for different austempering conditions. After 300 C isothermal treatments at intermediate times, the austenite is plastically stable at room temperature and contributes, together with the bainitic ferrite, to the proof stress and the toughness of the material. For austenite volume fractions higher than 25 pct, the proof stress is controlled by this phase and the toughness depends mainly on the stability of {gamma}. In these conditions (370 C and 410 C treatments), the present material exhibits a transformation-induced plasticity (TRIP) effect, which leads to an improvement in ductility. It is shown that the strain level necessary to initiate the martensitic transformation induced by deformation depends on the carbon content of the austenite. The martensite formed under TRIP conditions can be of two different types: autotempered plate martensite, which forms at room temperature from an austenite with a quasi-coherent epsilon carbide precipitation, and lath martensite nucleated at twin boundaries and twin intersections.

  19. Effect of Holding Time in the (α + γ) Temperature Range on Toughness of Specially Austempered Ductile Iron

    Science.gov (United States)

    Kobayashi, Toshiro; Yamada, Shinya

    1996-07-01

    Austempered ductile iron (ADI) finds wide application in the industry because of its high strength and toughness. The QB' process has been developed to produce a fine microstructure with high fracture toughness in ADI. This process involves reaustenitizing a prequenched ductile iron in the (α + γ) temperature range followed by an isothermal treatment in the bainitic transformation tem-perature range. In the present work, the effect of holding time in the (α + γ) temperature range on the structure and un-notched toughness of ADI has been studied. Prior to the austempering treatment, the as-cast ductile iron was heat treated to obtain martensitic, ferritic, and pearlitic matrix structures. In the case of prequenched material (martensitic matrix), the un-notched impact toughness increased as a function of holding time in the (α + γ) temperature range. The reaustenitization heat treatment also resulted in the precipitation of fine carbide particles, identified as (Fe,Cr,Mn)3C. It was shown that the increase in holding time in the (α + γ) temperature range leads to a reduction in the number of carbide particles. In the case of a ferritic prior structure, a long duration hold in the (α + γ) temperature range resulted in the coarsening of the structure with a marginal increase in the tough-ness. In the case of a pearlitic prior structure, the toughness increased with holding time. This was attributed to the decomposition of the relatively stable carbide around the eutectic cell boundary with longer holding times.

  20. Effect of holding time in the ({alpha} + {gamma}) temperature range on toughness of specially austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, T.; Yamada, S. [Toyohashi Univ. of Technology (Japan). Dept. of Production Systems Engineering

    1996-07-01

    Austempered ductile iron (ADI) finds wide application in the industry because of its high strength and toughness. The QB{prime} process has been developed to produce a fine microstructure with high fracture toughness in ADI. This process involves reaustenitizing a prequenched ductile iron in the ({alpha} + {gamma}) temperature range followed by an isothermal treatment in the bainitic transformation temperature range. In the present work, the effect of holding time in the ({alpha} + {gamma}) temperature range on the structure and un-notched toughness of ADI has been studied. Prior to the austempering treatment, the as-cast ductile iron was heat treated to obtain martensitic, ferritic, and pearlitic matrix structures. In the case of prequenched material (martensitic matrix), the un-notched impact toughness increased as a function of holding time in the ({alpha} + {gamma}) temperature range. The reaustenitization heat treatment also resulted in the precipitation of fine carbide particles, identified as (Fe,Cr,Mn){sub 3}C. It was shown that the increase in holding time in the ({alpha} + {gamma}) temperature range leads to a reduction in the number of carbide particles. In the case of a ferritic prior structure, a long duration hold in the ({alpha} + {gamma}) temperature range resulted in the coarsening of the structure with a marginal increase in the toughness. In the case of a pearlitic prior structure, the toughness increased with holding time. This was attributed to the decomposition of the relatively stable carbide around the eutectic cell boundary with longer holding times.

  1. Modification during heat treatment and application service of austempered ductile iron parts. ADI buhin no netsushori oyobi shiyochu no henkei

    Energy Technology Data Exchange (ETDEWEB)

    Shiokawa, T. (Subiyama Co. Ltd., Tokyo (Japan))

    1991-12-25

    Austempered ductile iron (ADI) has a very high mechanical strength, and excellent tenacity and ductility, but has also problems of dimensional changes in ADI parts. This paper describes dimensional changes in ADI parts, and further discusses points requiring cautions on dimensions when using ADI parts. To reduce dimensional changes before and after a heat treatment of an ADI, a use of ferrite is desirable as a texture before the heat treatment. Or otherwise the dimensional change due to heat treatment may be reflected initially on the dimensions before the heat treatment as an effective means of reducing the change. As an ADI varies its dimension-related thermal stability according to its chemical composition and the heat treatment method, parts that need the stability require a consideration to use a low Ni content and extend the austempering time. Since the ADI parts have different thermal expansion coefficient from the conventional ductile cast irons, parts subjected to a temperature rise should be used with considerations given to the thermal expansion difference with the mating parts. 4 refs., 4 figs., 3 tabs.

  2. Effect of austenitizing conditions on the impact properties of an alloyed austempered ductile iron of initially ferritic matrix structure

    Energy Technology Data Exchange (ETDEWEB)

    Delia, M.; Alaalam, M.; Grech, M. [Univ. of Malta (Malta). Dept. of Metallurgy and Materials

    1998-04-01

    The effect of austenitizing conditions on the microstructure and impact properties of an austempered ductile iron (ADI) containing 1.6% Cu and 1.6% Ni as the main alloying elements was investigated. Impact tests were carried out on samples of initially ferritic matrix structure and which had been first austenitized at 850, 900, 950, and 1,000 C for 15 to 360 min and austempered at 360 C for 180 min. Results showed that the austenitizing temperature, T{sub {gamma}}, and time, t{sub {gamma}} have a significant effect on the impact properties of the alloy. This has been attributed to the influence of these variables on the carbon kinetics. Microstructures of samples austenitized at 950 and 1,000 C contain no pro-eutectoid ferrite. The impact properties of the former structures are independent of t{sub {gamma}}, while those solution treated at 1,000 C are generally low and show wide variation over the range of soaking time investigated. For fully ausferritic structures, impact properties fall with an increase in T{sub {gamma}}. This is particularly evident at 1,000 C. As the T{sub {gamma}} increases, the amount of carbon dissolved in the original austenite increases. This slows down the rate of austenite transformation and results in coarser structures with lower mechanical properties. Optimum impact properties are obtained following austenitizing between 900 and 950 C for 120 to 180 min.

  3. Effect of the Linear Graphite on Austempered Austemper-Bainite Ductile Iron%线状石墨对奥-贝球铁性能影响的分析

    Institute of Scientific and Technical Information of China (English)

    张博

    2009-01-01

    @@ 板簧支座零件,选用奥-贝球铁AD11000-5,性能要求:抗拉强度≥1 000 MPa,伸长率≥5%,硬度300~360 HB;组织要求:球化级别1~3级,石墨大小5~7级,基体组织为中等或细小上贝氏体+20%~30%残余奥氏体.

  4. Magnetically levitated mesenchymal stem cell spheroids cultured with a collagen gel maintain phenotype and quiescence

    Directory of Open Access Journals (Sweden)

    Natasha S Lewis

    2017-04-01

    Full Text Available Multicellular spheroids are an established system for three-dimensional cell culture. Spheroids are typically generated using hanging drop or non-adherent culture; however, an emerging technique is to use magnetic levitation. Herein, mesenchymal stem cell spheroids were generated using magnetic nanoparticles and subsequently cultured within a type I collagen gel, with a view towards developing a bone marrow niche environment. Cells were loaded with magnetic nanoparticles, and suspended beneath an external magnet, inducing self-assembly of multicellular spheroids. Cells in spheroids were viable and compared to corresponding monolayer controls, maintained stem cell phenotype and were quiescent. Interestingly, core spheroid necrosis was not observed, even with increasing spheroid size, in contrast to other commonly used spheroid systems. This mesenchymal stem cell spheroid culture presents a potential platform for modelling in vitro bone marrow stem cell niches, elucidating interactions between cells, as well as a useful model for drug delivery studies.

  5. Spheroidal galactic halos and mirror dark matter

    CERN Document Server

    Foot, R

    2004-01-01

    Mirror matter has been proposed as a dark matter candidate. It has several very attractive features, including automatic stability and darkness, the ability to mimic the broad features of cold dark matter while in the linear density perturbation regime, and consistency with all direct dark matter search experiments, both negative (e.g. CDMS II) and positive (DAMA). In this paper we consider an important unsolved problem: Are there plausible reasons to explain why most of the mirror matter in spiral galaxies exists in the form of gaseous {\\it spheroidal} galactic halos around ordinary matter {\\it disks}? We compute an order-of-magnitude estimate that the mirror photon luminosity of a typical spiral galaxy today is around $10^{44}$ erg/s. Interestingly, this rate of energy loss is similar to the power supplied by ordinary supernova explosions. We discuss circumstances under which supernova power can be used to heat the gaseous part of the mirror matter halo and hence prevent its collapse to a disk. The {\\it mac...

  6. Life and times of dwarf spheroidal galaxies

    CERN Document Server

    Salvadori, S; Schneider, R

    2008-01-01

    We propose a cosmological scenario for the formation and evolution of dwarf spheroidal galaxies (dSphs), satellites of the Milky Way (MW). An improved version of the semi-analytical code GAMETE (GAlaxy Merger Tree & Evolution) is used to follow the dSphs evolution simultaneously with the MW formation, matching the observed properties of both. In this scenario dSph galaxies represent fossil objects virializing at z = 7.2 +/- 0.7 (i.e. in the pre-reionization era z > z_rei = 6) in the MW environment, which at that epoch has already been pre-enriched up to [Fe/H] ~ -3; their dynamical masses are in the narrow range M = (1.6 +/- 0.7) x 10^8 M_sun, although a larger spread might be introduced by a more refined treatment of reionization. Mechanical feedback effects are dramatic in such low-mass objects, causing the complete blow-away of the gas ~100 Myr after the formation epoch: 99% of the present-day stellar mass, M_* = (3 +/- 0.7) x 10^6 M_sun, forms during this evolutionary phase, i.e. their age is >13 Gyr....

  7. Testing modified gravity with dwarf spheroidal galaxies

    CERN Document Server

    Haghi, Hosein

    2016-01-01

    The observed velocity dispersion of the classical dwarf spheroidal (dSph) galaxies of the Milky Way (MW) requires the Newtonian stellar mass-to-light ($M_*/L$) ratios in the range of about 10 to more than 100 solar units that are well outside the acceptable limit predicted by stellar population synthesis models. Using Jeans analysis, we calculate the line-of-sight velocity dispersion ($\\sigma_{\\emph{los}}$) of stars in eight MW dSphs in the context of the modified gravity (MOG) theory of Moffat, assuming a constant $M_*/L$ ratio without invoking the exotic cold dark matter. First, we use the weak field approximation of MOG and assume the two parameters $ \\alpha $ and $ \\mu $ of the theory to be constant as has already been inferred from fitting to the observed rotational data of The HI Nearby Galaxy Survey catalogue of galaxies. We find that the derived $M_*/L$ ratios for almost all dSphs are too large to be explained by the stellar population values. In order to fit the line-of-sight velocity dispersions of ...

  8. Testing modified gravity with dwarf spheroidal galaxies

    Science.gov (United States)

    Haghi, Hosein; Amiri, Vahid

    2016-12-01

    The observed velocity dispersion of the classical dwarf spheroidal (dSph) galaxies of the Milky Way (MW) requires the Newtonian stellar mass-to-light (M*/L) ratios in the range of about 10 to more than 100 solar units that are well outside the acceptable limit predicted by stellar population synthesis models. Using Jeans analysis, we calculate the line-of-sight velocity dispersion (σlos) of stars in eight MW dSphs in the context of the modified gravity (MOG) theory of Moffat, assuming a constant M*/L ratio without invoking the exotic cold dark matter. First, we use the weak field approximation of MOG and assume the two parameters α and μ of the theory to be constant as has already been inferred from fitting to the observed rotational data of The H I Nearby Galaxy Survey catalogue of galaxies. We find that the derived M*/L ratios for almost all dSphs are too large to be explained by the stellar population values. In order to fit the line-of-sight velocity dispersions of the dSph with reasonable M*/L values, we must vary α and μ on a case by case basis. A common pair of values cannot be found for all dSphs. Comparing with the values found from rotation curve fitting, it appears that μ correlates strongly with galaxy luminosity, shedding doubt on it as a universal constant.

  9. Effect of low temperatures on charpy impact toughness of austempered ductile irons

    Science.gov (United States)

    Riabov, Mikhail V.; Lerner, Yury S.; Fahmy, Mohammed F.

    2002-10-01

    Impact properties of standard American Society for Testing Materials (ASTM) grades of austempered ductile iron (ADI) were evaluated at subzero temperatures in unnotched and V-notched conditions and compared with ferritic and pearlitic grades of ductile irons (DIs). It was determined that there is a decrease in impact toughness for all ADI grades when there is a decrease in content of retained austenite and a decrease in test temperature, from room temperature (RT) to -60 °C. However, the difference in impact toughness values was not so noticeable for low retained austenite containing grade 5 ADI at both room and subzero temperatures as it was for ADI grade 1. Furthermore, the difference in impact toughness values of V-notched specimens of ADI grades 1 and 5 tested at -40 °C was minimal. The impact behaviors of ADI grade 5 and ferritic DI were found to be more stable than those of ADI grades 1, 2, 3, and 4 and pearlitic DI when the testing temperature was decreased. The impact toughness of ferritic DI was higher than that of ADI grades 1 and 2 at both -40 °C and -60 °C. The impact properties of ADI grades 4 and 5 were found to be higher than that of pearlitic DI at both -40 °C and -60 °C. The scanning electron microscopy (SEM) study of fracture surfaces revealed mixed ductile and quasicleavage rupture morphology types in all ADI samples tested at both -40 °C and -60 °C. With decreasing content of retained austenite and ductility, the number of quasicleavage facets increased from ADI grade 1-5. It was also found that fracture morphology of ADI did not experience significant changes when the testing temperature decreased. Evaluation of the bending angle was used to support impact-testing data. Designers and users of ADI castings may use the data developed in this research as a reference.

  10. Bromine intercalated graphite for lightweight composite conductors

    KAUST Repository

    Amassian, Aram

    2017-07-20

    A method of fabricating a bromine-graphite/metal composite includes intercalating bromine within layers of graphite via liquid-phase bromination to create brominated-graphite and consolidating the brominated-graphite with a metal nanopowder via a mechanical pressing operation to generate a bromine-graphite/metal composite material.

  11. Human Cardiac Progenitor Spheroids Exhibit Enhanced Engraftment Potential.

    Directory of Open Access Journals (Sweden)

    Francesca Oltolina

    Full Text Available A major obstacle to an effective myocardium stem cell therapy has always been the delivery and survival of implanted stem cells in the heart. Better engraftment can be achieved if cells are administered as cell aggregates, which maintain their extra-cellular matrix (ECM. We have generated spheroid aggregates in less than 24 h by seeding human cardiac progenitor cells (hCPCs onto methylcellulose hydrogel-coated microwells. Cells within spheroids maintained the expression of stemness/mesenchymal and ECM markers, growth factors and their cognate receptors, cardiac commitment factors, and metalloproteases, as detected by immunofluorescence, q-RT-PCR and immunoarray, and expressed a higher, but regulated, telomerase activity. Compared to cells in monolayers, 3D spheroids secreted also bFGF and showed MMP2 activity. When spheroids were seeded on culture plates, the cells quickly migrated, displaying an increased wound healing ability with or without pharmacological modulation, and reached confluence at a higher rate than cells from conventional monolayers. When spheroids were injected in the heart wall of healthy mice, some cells migrated from the spheroids, engrafted, and remained detectable for at least 1 week after transplantation, while, when the same amount of cells was injected as suspension, no cells were detectable three days after injection. Cells from spheroids displayed the same engraftment capability when they were injected in cardiotoxin-injured myocardium. Our study shows that spherical in vivo ready-to-implant scaffold-less aggregates of hCPCs able to engraft also in the hostile environment of an injured myocardium can be produced with an economic, easy and fast protocol.

  12. Graphite/Epoxy Deicing Heater

    Science.gov (United States)

    Hung, Ching-Cheh; Dillehay, Michael E.; Stahl, Mark

    1988-01-01

    Heat applied close to surface protected. One ply of highly electrically- and thermally-conductive brominated-graphite fiber composite laminated between two plies of electrically-insulating composite material, with michel foil making contact with end portions of graphite fibers. Part of foil exposed beyond composite to serve as electrical contact. Graphite/Epoxy composite heater developed to prevent and reverse formation of ice on advanced composite surfaces of aircraft.

  13. Heat exchanger using graphite foam

    Science.gov (United States)

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

    A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

  14. Practical Rhumb Line Calculations on the Spheroid

    Science.gov (United States)

    Bennett, G. G.

    About ten years ago this author wrote the software for a suite of navigation programmes which was resident in a small hand-held computer. In the course of this work it became apparent that the standard text books of navigation were perpetuating a flawed method of calculating rhumb lines on the Earth considered as an oblate spheroid. On further investigation it became apparent that these incorrect methods were being used in programming a number of calculator/computers and satellite navigation receivers. Although the discrepancies were not large, it was disquieting to compare the results of the same rhumb line calculations from a number of such devices and find variations of some miles when the output was given, and therefore purported to be accurate, to a tenth of a mile in distance and/or a tenth of a minute of arc in position. The problem has been highlighted in the past and the references at the end of this show that a number of methods have been proposed for the amelioration of this problem. This paper summarizes formulae that the author recommends should be used for accurate solutions. Most of these may be found in standard geodetic text books, such as, but also provided are new formulae and schemes of solution which are suitable for use with computers or tables. The latter also take into account situations when a near-indeterminate solution may arise. Some examples are provided in an appendix which demonstrate the methods. The data for these problems do not refer to actual terrestrial situations but have been selected for illustrative purposes only. Practising ships' navigators will find the methods described in detail in this paper to be directly applicable to their work and also they should find ready acceptance because they are similar to current practice. In none of the references cited at the end of this paper has the practical task of calculating, using either a computer or tabular techniques, been addressed.

  15. Photoluminescent carbon nanotubes interrogate the permeability of multicellular tumor spheroids

    Science.gov (United States)

    Shah, Janki; Roxbury, Daniel; Paknejad, Navid; Heller, Daniel A.

    2015-01-01

    Nanomaterials have been extensively investigated for cancer drug delivery and imaging applications. Nanoparticles that show promise in two-dimensional cell culture systems often fail in more complex environments, possibly due to the lack of penetration in dense, three-dimensional structures. Multicellular tumor spheroids are an emerging model system to investigate interactions of nanoparticles with 3D in vitro cell culture environments. Using the intrinsic near-infrared emission of semiconducting carbon nanotubes to optically reconstruct their localization within a three-dimensional volume, we resolved the relative permeability of two different multicellular tumor spheroids. Nanotube photoluminescence revealed that nanotubes rapidly internalized into MCF-7 breast cancer cell-derived spheroids, whereas they exhibited little penetration into spheroids derived from SK-136, a cell line that we developed from murine liver cancer. Characterization of the spheroids by electron microscopy and immunohistochemistry revealed large differences in the extracellular matrix and interstitial spacing, which correlated directly with nanotube penetration. This platform portends a new approach to characterize the permeability of living multicellular environments. PMID:26456974

  16. Effects of Austempered Temperature on Microstructure and Properties of CADI%等温淬火温度对CADI组织及性能的影响

    Institute of Scientific and Technical Information of China (English)

    孙玉福; 张婷; 赵靖宇; 刘金庆; 吴娜; 徐栩

    2011-01-01

    In this paper, the effects of austempered temperature on the morphology of bainite,contents of retained austenite, mechanical properties and wear resistance of carbide austempered ductile iron (CADI) were researched and the impact fracture mechanism was analyzed. The samples whose as-cast microstructures composed of 75% pearlite+ferrite+10% carbide, were .austenited at 920 ℃ for 1.5 h and then austempered at 240 ℃, 280 ℃ and 320 ℃ for 2 h, respectively.The results show that with the increase of austempered temperature the morphology of bainite changes from needle to featheriness; the residual austenite content increases; the impact toughness increases and the hardness and relative wear resistance reduces. After austempering at the optimal temperature 280 ℃, the microstructure is composed of bainite, 22.33% retained austenite and 10% carbide. Its hardness is HRC 50.9, impact toughness is 32.72 J/cm2, and the relative wear resistance rises by 11% than that of the samples austempered at 320 ℃. The fracture morphology of the CADI exhibits a mixed fracture characteristic.%针对含一定碳化物等温淬火球墨铸铁(CADI),研究了等温淬火温度对贝氏体相形貌、残余奥氏体量、力学性能及耐磨性能的影响,分析了冲击断裂机理.结果表明,对于铸态组织为75%珠光体+铁素体+10%碳化物试样,经920℃×1.5 h奥氏体化后,在240℃,280℃及320℃进行等温淬火处理2h,随着等淬温度的提高,贝氏体的形貌由针状变粗至羽毛状,残余奥氏体量增加,硬度减低,冲击韧度提高,相对耐磨性降低.最佳等温淬火温度为280℃,此热处理工艺后组织为贝氏体+22.33%残余奥氏体+10%碳化物,硬度HRC 50.9,冲击韧度32.72 J/c㎡,断口呈混合断裂特征,相对耐磨性比320℃时增加11%.

  17. Flexible PVC flame retarded with expandable graphite

    CSIR Research Space (South Africa)

    Focke, WW

    2014-02-01

    Full Text Available by the polymer matrix and the exfoliating graphite prevents the formation of a flammable air fuel mixture. Keywords: Expandable graphite; graphite oxide; graphite intercalation compound; exfoliation; thermal analysis ________________ *Corresponding author: Tel... char residue [6] and this contributes to the mechanisms of flame retardant action [5]. Expandable graphite (EG) is a partially oxidized form of graphite containing intercalated guest species (e.g., sulfuric acid anions) in-between the stacked...

  18. Graphite in Science and Nuclear Technique

    OpenAIRE

    Zhmurikov, E. I.; Bubnenkov, I. A.; Dremov, V. V.; Samarin, S. I.; Pokrovsky, A. S.; Harkov, D. V.

    2013-01-01

    The monograph is devoted to the application of graphite and graphite composites in science and technology. The structure and electrical properties, the technological aspects of production of high-strength synthetic graphites, the dynamics of the graphite destruction, traditionally used in the nuclear industry are discussed. It is focuses on the characteristics of graphitization and properties of graphite composites based on carbon isotope 13C. The book is based, generally, on the original res...

  19. Graphitic packing removal tool

    Energy Technology Data Exchange (ETDEWEB)

    Meyers, K.E.; Kolsun, G.J.

    1996-12-31

    Graphitic packing removal tools are described for removal of the seal rings in one piece from valves and pumps. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  20. Influencia de los factores microestructurales en la resistencia al desgaste por deslizamiento de las fundiciones nodulares austemperadas. // Influence of the microstructure factors in the sliding wear resistance of austempered cast ductile iron.

    Directory of Open Access Journals (Sweden)

    C. J. Diez Cicero

    2008-09-01

    Full Text Available Entre los materiales metálicos de mayor demanda, el hierro dúctil con grafito esferoidal o nodular ocupa en la actualidaduno de los lugares más importantes entre los hierros fundidos de alta resistencia. Desde hace unos veinticinco años laintroducción del hierro nodular austemperado significó de hecho una revolución en el campo de las aleaciones ferrosas. Enel presente trabajo se realiza un estudio de la influencia del conteo de nódulos de grafito del hierro nodular en el proceso deaustemperado, a partir de las características de las estructuras obtenidas, por la variación de la cantidad de nódulos degrafito y de las variables de tratamiento térmico. Dichas estructuras son sometidas a la acción del desgaste, en este caso aun desgaste por deslizamiento mediante un ensayo típico disco-zapata. Con los resultados obtenidos, se realiza un análisisestadístico de la influencia del conteo de nódulos en dichas propiedades y de las causas de este comportamiento, tomandoen consideración la interrelación del conteo de nódulos con las variables de tratamiento térmico utilizadas en las muestrasensayadas y su incidencia en el mecanismo de desgaste.Palabras claves: Hierro nodular, conteo de nódulos, austemperado, desgaste por deslizamiento.____________________________________________________________________________Abstract:A study about the influence of the graphite nodules quantity and some heat treatment parameters in the characteristic of castductile iron is presented. Experimental investigation of wear resistance by sliding is applied to specimens tested ofaustempered ductile irons using a test machine based in the disc- plate system. Statistical analysis about the influence of thegraphite nodule quantity in the wear resistance properties, so as well as, the causes of this behaviour taking into account thegraphite nodule count and some heat treatment variables is done.Key words: austempered ductile iron, graphite nodules, wear

  1. Stokesian swimming of a prolate spheroid at low Reynolds number

    CERN Document Server

    Felderhof, B U

    2016-01-01

    The swimming of a spheroid immersed in a viscous fluid and performing surface deformations periodically in time is studied on the basis of Stokes equations of low Reynolds number hydrodynamics. The average over a period of time of the swimming velocity and the rate of dissipation are given by integral expressions of second order in the amplitude of surface deformations. The first order flow velocity and pressure, as functions of spheroidal coordinates, are expressed as sums of basic solutions of Stokes equations. Sets of superposition coefficients of these solutions which optimize the mean swimming speed for given power are derived from an eigenvalue problem. The maximum eigenvalue is a measure of the efficiency of the optimal stroke within the chosen class of motions. The maximum eigenvalue for sets of low order is found to be a strongly increasing function of the aspect ratio of the spheroid.

  2. The effect of gravitational tides on dwarf spheroidal galaxies

    CERN Document Server

    Nichols, Matthew; Jablonka, Pascale

    2014-01-01

    The effect of the local environment on the evolution of dwarf spheroidal galaxies is poorly understood. We have undertaken a suite of simulations to investigate the tidal impact of the Milky Way on the chemodynamical evolution of dwarf spheroidals that resemble present day classical dwarfs using the SPH code GEAR. After simulating the models through a large parameter space of potential orbits the resulting properties are compared with observations from both a dynamical point of view, but also from the, often neglected, chemical point of view. In general, we find that tidal effects quench the star formation even inside gas-endowed dwarfs. Such quenching, may produce the radial distribution of dwarf spheroidals from the orbits seen within large cosmological simulations. We also find that the metallicity gradient within a dwarf is gradually erased through tidal interactions as stellar orbits move to higher radii. The model dwarfs also shift to higher $\\langle$[Fe/H]$\\rangle$/L ratios, but only when losing $>$$20...

  3. Induction plasma spheroidization of tungsten and molybdenum powders

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The melting, evaporation and oxidation behaviors as well as the solidification phenomena of tungsten and molybdenum in induction plasma were studied. Scanning electron microscopy was used to examine the morphology and the cross section of plasma-processed powders. X-ray diffraction was used to analyze the oxides formed on the particle surface of these two metals. The influence of spray chamber pressure on the spheroidization and oxidation phenomena was discussed. The results show that fewer Mo particles than W particles are spheroidized at the same powder feed rate under the same plasma spray condition although molybdenum has a lower melting point. A small fraction of tungsten is evaporized and condensed either on the surface of tungsten particles nearby or on the wall of spray chamber. Tungsten oxides were found in tungsten powder processed under soft vacuum condition. Extremely large grains form inside some spheroidized particles of tungsten powder.

  4. Numerical Study of the Sedimentation of Spheroidal Particles

    CERN Document Server

    Ardekani, Mehdi Niazi; Breugem, Wim-Paul; Brandt, Luca

    2016-01-01

    The gravity-driven motion of rigid particles in a viscous fluid is relevant in many natural and industrial processes, yet this has mainly been investigated for spherical particles. We therefore consider the sedimentation of non-spherical (spheroidal) isolated and particle pairs in a viscous fluid via numerical simulations using the Immersed Boundary Method. The simulations performed here show that the critical Galileo number for the onset of secondary motions decreases as the spheroid aspect ratio departs from 1. Above this critical threshold, oblate particles perform a zigzagging motion whereas prolate particles rotate around the vertical axis while having their broad side facing the falling direction. Instabilities of the vortices in the wake follow when farther increasing the Galileo number. We also study the drafting-kissing-tumbling associated with the settling of particle pairs. We find that the interaction time increases significantly for non-spherical particles and, more interestingly, spheroidal part...

  5. Centrifugal force induced by relativistically rotating spheroids and cylinders

    CERN Document Server

    Katz, Joseph; Bicak, Jiri; 10.1088/0264-9381/28/6/065004

    2011-01-01

    Starting from the gravitational potential of a Newtonian spheroidal shell we discuss electrically charged rotating prolate spheroidal shells in the Maxwell theory. In particular we consider two confocal charged shells which rotate oppositely in such a way that there is no magnetic field outside the outer shell. In the Einstein theory we solve the Ernst equations in the region where the long prolate spheroids are almost cylindrical; in equatorial regions the exact Lewis "rotating cylindrical" solution is so derived by a limiting procedure from a spatially bound system. In the second part we analyze two cylindrical shells rotating in opposite directions in such a way that the static Levi-Civita metric is produced outside and no angular momentum flux escapes to infinity. The rotation of the local inertial frames in flat space inside the inner cylinder is thus exhibited without any approximation or interpretational difficulties within this model. A test particle within the inner cylinder kept at rest with respect...

  6. Monoenergetic electron parameters in a spheroid bubble model

    Institute of Scientific and Technical Information of China (English)

    H.Sattarian; Sh.Rahmatallahpur; T.Tohidi

    2013-01-01

    A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived.The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately,especially at the relativistic region.The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model.The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons △E/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions.As a result,the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model.

  7. Cell proliferation kinetics and radiation response in 9L tumor spheroids

    Energy Technology Data Exchange (ETDEWEB)

    Sweigert, S.E.

    1984-05-01

    Cell kinetic parameters, including population doubling-time, cell cycle time, and growth fraction, were measured in 9L gliosarcoma spheroids. These parameters were studied as the spheroids grew from 50 ..mu..m to over 900 ..mu..m in diameter. Experiments relating the cell kinetic parameters to the radiation response of 9L spheroids were also carried out. The major findings were that the average cell cycle time (T/sub c/), is considerably longer in large spheroids than in exponentially-growing monolayers, the radiosensitivity of noncycling (but still viable) cells in spheroids is not significantly different from that of cycling spheroid cells, and the radiation-induced division delay is approximately twice as long in spheroid cells as in monolayer cells given equal radiation doses. The cell loss factor for spheroids of various sizes was calculated, by using the measured kinetic parameters in the basic equations for growth of a cell population. 157 references, 6 figures, 3 tables.

  8. Study of the Chemotactic Response of Multicellular Spheroids in a Microfluidic Device

    Science.gov (United States)

    Ayuso, Jose M.; Basheer, Haneen A.; Monge, Rosa; Sánchez-Álvarez, Pablo; Doblaré, Manuel; Shnyder, Steven D.; Vinader, Victoria; Afarinkia, Kamyar

    2015-01-01

    We report the first application of a microfluidic device to observe chemotactic migration in multicellular spheroids. A microfluidic device was designed comprising a central microchamber and two lateral channels through which reagents can be introduced. Multicellular spheroids were embedded in collagen and introduced to the microchamber. A gradient of fetal bovine serum (FBS) was established across the central chamber by addition of growth media containing serum into one of the lateral channels. We observe that spheroids of oral squamous carcinoma cells OSC–19 invade collectively in the direction of the gradient of FBS. This invasion is more directional and aggressive than that observed for individual cells in the same experimental setup. In contrast to spheroids of OSC–19, U87-MG multicellular spheroids migrate as individual cells. A study of the exposure of spheroids to the chemoattractant shows that the rate of diffusion into the spheroid is slow and thus, the chemoattractant wave engulfs the spheroid before diffusing through it. PMID:26444904

  9. Fusion of uniluminal vascular spheroids: a model for assembly of blood vessels.

    Science.gov (United States)

    Fleming, Paul A; Argraves, W Scott; Gentile, Carmine; Neagu, Adrian; Forgacs, Gabor; Drake, Christopher J

    2010-02-01

    We evaluated the self-assembly properties of uniluminal vascular spheroids having outer layers of vascular smooth muscle cells and a contiguous inner layer of endothelial cells lining a central lumen. We showed that while pairs of uniluminal vascular spheroids suspended in culture medium fused to form a larger diameter spheroidal structure, spheroids in collagen hydrogels formed elongated structures. These findings highlight the potential use of uniluminal vascular spheroids as modules to engineer blood vessels. We also demonstrate that uniluminal vascular spheroid fusion conforms to models describing the coalescence of liquid drops. Furthermore, the fusion of uniluminal vascular spheroids in vitro closely resembled the in vivo process by which the descending aorta forms from the fusion of the paired dorsal aortae during embryonic development. Together, the findings indicate that tissue liquidity underlies uniluminal vascular spheroid fusion and that in vivo anastomosis of blood vessels may involve a similar mechanism.

  10. Graphite intercalation compounds and applications

    CERN Document Server

    Enoki, Toshiaki; Endo, Morinobu

    2003-01-01

    1. Introduction. 2. Synthesis and Intercalation Chemistry. 3. Structures and Phase Transitions. 4. Lattice Dynamics. 5. Electronic Structures. 6. Electron Transport Properties. 7. Magnetic Properties. 8. Surface Properties and Gas Adsorption. 9. GICs and Batteries. 10. Highly Conductive Graphite Fibers. 11. Exfoliated Graphite Formed by Intercalation. 12. Intercalated Fullerenes and Carbon Nanotubes. Index

  11. Cryotribology of diamond and graphite

    Energy Technology Data Exchange (ETDEWEB)

    Iwasa, Yukikazu; Ashaboglu, A.F.; Rabinowicz, E.R. [Francis Bitter Magnet Lab., Cambridge, MA (United States)

    1996-12-31

    An experimental study was carried out on the tribological behavior of materials of interest in cryogenic applications, focusing on diamond and graphite. Both natural diamond (referred in the text as diamond) and chemical-vapor-deposition (CVD) diamond (CVD-diamond) were used. The experiment was carried out using a pin-on-disk tribometer capable of operating at cryogenic temperatures, from 4.2 to 293 K. Two basic scenarios of testing were used: (1) frictional coefficient ({mu}) vs velocity (v) characteristics at constant temperatures; (2) {mu} vs temperature (T) behavior at fixed sliding speeds. For diamond/CVD-diamond, graphite/CVD-diamond, stainless steel/CVD-diamond pairs, {mu}`s are virtually velocity independent. For each of diamond/graphite, alumina/graphite, and graphite/graphite pairs, the {partial_derivative}{mu}/{partial_derivative}v characteristic is favorable, i.e., positive. For diamond/CVD-diamond and graphite/CVD-diamond pairs, {mu}`s are nearly temperature independent between in the range 77 - 293 K. Each {mu} vs T plot for pin materials sliding on graphite disks has a peak at a temperature in the range 100 - 200 K.

  12. Fatigue crack growth in austempered ductile and grey cast irons - stress ratio effects in air and mine water

    Energy Technology Data Exchange (ETDEWEB)

    James, M.N. [Plymouth Univ. (United Kingdom). Dept. of Mech. and Marine Eng.; Li Wenfong [Department of Mechanical Engineering, University of Sydney, Sydney, NSW 2006 (Australia)

    1999-06-15

    A study is presented of the effect of stress ratio on fatigue crack growth in grey (GI) and austempered ductile (ADI) cast irons in laboratory air and, for the ADI, in synthetic mine water. Fatigue crack closure was measured by compliance techniques and factored out of the applied {Delta}K values ({Delta}K=K{sub max}-K{sub min}) to give effective stress intensity values. Crack growth rate modelling was then attempted for the laboratory air data using a two-parameter approach ({Delta}K and K{sub max}). This worked well for the ADI, but not for the GI, probably due to the much larger scatter inherent in the fatigue crack growth rates in the latter alloy. Trends in the observed growth rate and closure data for the two alloys are explained in terms of mechanism changes arising from microstructural/crack tip plastic zone interactions, and K{sub max} effects. (orig.) 9 refs.

  13. Effects of Austempering after Hot Deformation on the Mechanical Properties of Hot Rolled Si-Mn TRIP Steel Sheets

    Institute of Scientific and Technical Information of China (English)

    LI Zhuang; ZHANG Ping-li; WU Di

    2004-01-01

    Excellent mechanical properties are obtained by austempering after hot deformation without subsequent heat treatment in the present Si-Mn TRIP steel sheets. Isothermal holding time after finishing rolling has affected the mechanical properties of this steel. The results show that the sample exhibits a good combination of ultimate tensile strength and total elongation when it is held at the bainite transformation temperature after hot deformation. The stability of retained austenite increases with an increase of isothermal holding time, and a further increase in the holding duration results in a decrease of it. The tensile strength, total elongation and strength ductility reach the maximum values(774MPa, 33% and 25542MPa% respectively) for this sort of hot rolled Si-Mn TRIP steel using the optimal technology.

  14. Isothermal Transformation of Austempered Ductile Iron and ADI Continuous Production Line%等温淬火球铁的等温转变过程及ADI设备

    Institute of Scientific and Technical Information of China (English)

    王蕾; 吴光英

    2012-01-01

    分析了等温淬火球铁(ADI)等温转变过程及影响因素,介绍了奥一贝球铁等温淬火设备,包括推杆式、立式、箱式等温淬火连续生产线,并对国内外等温淬火生产线进行了对比。%The isothermal transformation of austempered ductile iron and main influence factors were described. The austempered ductile iron continuous production lines, including pusher type, vertical type and box type were introduced, and the ADI production lines at home and abroad were compared.

  15. Effect of austenitizing conditions on the impact properties of an alloyed austempered ductile iron of initially ferritic matrix structure

    Science.gov (United States)

    Delia, M.; Alaalam, M.; Grech, M.

    1998-04-01

    The effect of austenitizing conditions on the microstructure and impact properties of an austempered ductile iron (ADI) containing 1.6% Cu and 1.6% Ni as the main alloying elements was investigated. Impact tests were carried out on samples of initially ferritic matrix structure and which had been first austenitized at 850,900, 950, and 1000°C for 15 to 360 min and austempered at 360°C for 180 min. Results showed that the austenitizing temperature, Tγ, and time, tγ, have a significant effect on the impact properties of the alloy. This has been attributed to the influence of these variables on the carbon kinetics. The impact energy is generally high after short tγ, and it falls with further soaking. In samples austenitized at 850 and 900°C, these trends correspond to the gradual disappearance of the pro-eutectoid ferrite and the attainment of fully developed ausferritic structures. In initially ferritic structures, the carbon diffusion distances involved during austenitization are large compared to those in pearlitic structures. This explains the relatively long soaking periods required to attain fully ausferritic structures, which in spite of the lower impact energy values, have a better combination of mechanical properties. Microstructures of samples austenitized at 950 and 1000°C contain no pro-eutectoid ferrite. The impact properties of the former structures are independent of tγ, while those solution treated at 1000°C are generally low and show wide variation over the range of soaking time investigated. For fully ausferritic structures, impact properties fall with an increase in Tγ. This is particularly evident at 1000°C. As the Tγ increases, the amount of carbon dissolved in the original austenite increases. This slows down the rate of austenite transformation and results in coarser structures with lower mechanical properties. Optimum impact properties are obtained following austenitizing between 900 and 950°C for 120 to 180 min.

  16. Effect of Phenomena Accompanying Wear in Dry Corundum Abrasive on the Properties and Microstructure of Austempered Ductile Iron with Different Chemical Composition

    Directory of Open Access Journals (Sweden)

    Myszka D.

    2015-04-01

    Full Text Available The research described in this article is a fragment in the series of published works trying to determine the applicability of new materials for parts of the mining machinery. Tests were performed on two groups of austempered ductile iron - one of which contained 1.5% Ni and 0.5% Mo, while the other contained 1.9% Ni and 0.9% Cu. Each group has been heat treated according to the three different heat treatment variants and then the material was subjected to detailed testing of mechanical properties and abrasion wear resistance, measuring also hardness and magnetic properties, and conducting microstructural examinations. The results indicated that each of the tested materials was senstive to the surface hardening effect, which resulted in high wear resistance. It has been found that high temperature of austempering, i.e. 370°C, favours high wear resistance of ductile iron containing nickel and molybdenum. Low temperature of austempering, i.e. 270°C, develops high wear resistance in ductile iron containing nickel and copper. Both these materials offer completely different mechanical properties and as such can be used for different and specific applications.

  17. The Application of Acoustic Emission and Artificial Neural Networks in an Analysis of Kinetics in the Phase Transformation of Tool Steel During Austempering

    Directory of Open Access Journals (Sweden)

    Łazarska M.

    2017-06-01

    Full Text Available During the course of the study it involved tool steel C105U was used. The steel was austempered at temperatures of 130°C, 160°C and 180°C respectively. Methods of acoustic emission (AE were used to investigate the resulting effects associated with transformations and a large number of AE events were registered. Neural networks were applied to analyse these phenomena. In the tested signal, three groups of events were identified of: high, medium and low energy. The average spectral characteristics enabled the power of the signal spectrum to be determined. After completing the process, the results were compiled in the form of diagrams of the relationship of the AE incidence frequency as a function of time. Based on the results, it was found that in the austempering of tool steel, in the first stage of transformation midrib morphology is formed. Midrib is a twinned thin plate martensite. In the 2nd stage of transformation, the intensity of the generation of medium energy events indicates the occurrence of bainite initialised by martensite. The obtained graphic of AE characteristics of tool steel austempering allow conclusions to be drawn about the kinetics and the mechanism of this transformation.

  18. The Birth of Open Separation on a Prolate Spheroid

    Science.gov (United States)

    1988-09-01

    Vollmers (1983), and Costis, Polen , Hoang and Telionis (1988), will agree in detail with the solu- tions of the model problem but the latter allows the...7, pp. 435-454. Costis, C.E., Polen , D.M. Hoang, N.T. and Telionis, D.P. 1988 Laminar Separating Flow Over a Prolate Spheroid. To be published in J

  19. Sulphur, zinc and carbon in the Sculptor dwarf spheroidal galaxy

    NARCIS (Netherlands)

    Skúladóttir, Ása

    2016-01-01

    The Sculptor dwarf spheroidal galaxy is a Milky Way satellite with predominantly old stellar population, and therefore the ideal target to study early chemical evolution. The chemical abundances of photospheres of stars reveal the composition of their birth environment; studying stars of different a

  20. Building blocks of the Milky Way's accreted spheroid

    NARCIS (Netherlands)

    van Oirschot, Pim; Starkenburg, Else; Helmi, Amina; Nelemans, Gijs

    2017-01-01

    In the $\\Lambda$CDM model of structure formation, a stellar spheroid grows by the assembly of smaller galaxies, the so-called building blocks. Combining the Munich-Groningen semi-analytical model of galaxy formation with the high resolution Aquarius simulations of dark matter haloes, we study the

  1. Axisymmetric acoustic scattering from submerged prolate spheroidal shells

    Science.gov (United States)

    Boisvert, Jeffrey E.; Hayek, Sabih I.

    2005-09-01

    The equations of motion for nonaxisymmetric vibration of prolate spheroidal shells of constant thickness were derived using Hamilton's principle [S. I. Hayek and J. E. Boisvert, J. Acoust. Soc. Am. 114, 2799-2811 (2003)]. The shell theory used in this derivation includes shear deformations and rotatory inertias. The shell displacements and rotations were expanded in infinite series of comparison functions. These include associated Legendre functions in terms of the prolate spheroidal angular coordinate and circular functions in the azimuthal angle coordinate. The shell is insonified by a plane wave incident along the major axis. The external (heavy) fluid loading impedance was computed using an eigenfunction expansion of prolate spheroidal wavefunctions. Far-field scattered acoustic pressure spectra are presented for several shell thickness-to-half-length ratios ranging from 0.005 to 0.1, and for various shape parameters, a, ranging from an elongated spheroidal shell (a=1.01) to a spherical shell (a~100). The far-field directivity of acoustic scattering is presented at selected frequencies. [Work supported by the ONR/ASEE Summer Faculty Research Program.

  2. Analytical Equation for Estimating Terminal Velocities of Spheroidal Particles

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, Douglas W.

    2007-06-01

    An analytical method for estimating the terminal velocities of spheroidal particles in a fluid medium has been derived form a graphical approach proposed by Haider and Levenspiel. Using an analytical equation enables the researcher to calculate the terminal velocities without resorting to graphical interpolations, thereby reducing errors and enabling terminal velocities to be estimated in automated calculations.

  3. The mass content of the Sculptor dwarf spheroidal galaxy

    NARCIS (Netherlands)

    Battaglia, G.; Helmi, A.; Tolstoy, E.; Irwin, M.; Andersen, J; BlandHawthorn, J; Nordstrom, B

    2009-01-01

    We present a new determination of the mass content of the Sculptor dwarf spheroidal galaxy, based on a novel approach which takes into account the two distinct stellar populations present in this galaxy. This method helps to partially break the well-known mass-anisotropy degeneracy present in the mo

  4. Building blocks of the Milky Way's accreted spheroid

    NARCIS (Netherlands)

    van Oirschot, Pim; Starkenburg, Else; Helmi, Amina; Nelemans, Gijs

    2017-01-01

    In the $\\Lambda$CDM model of structure formation, a stellar spheroid grows by the assembly of smaller galaxies, the so-called building blocks. Combining the Munich-Groningen semi-analytical model of galaxy formation with the high resolution Aquarius simulations of dark matter haloes, we study the as

  5. Estimation of scattering from a moist rough surface with spheroidal dust particles

    Indian Academy of Sciences (India)

    Mukesh Kumar

    2009-08-01

    The scattering from moisture rough surface with spheroidal dust particles having surface with spheroidal dust particles has recently received much attention. In part due to the recent prediction and observation of the spheroidal dust particles in rough surfaces under elastic wave by the Kirchhoff scattering model and scalar approximation with slope. Our analysis shows that the scattering depends on the moisture (2–4.5%) with spheroidal dust particles. At slightly moisture rough surface the dielectric properties increase with change in field amplitude in a rough surface with spheroidal dust particles.

  6. Mechanism of the Forming of Nodular Graphite

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This article presents a theory about the growth mechanism of bubble-screw dislocation of nodular graphite. Normally speaking, the crystallizing procedure of most nodular graphite is as follows: firstly, graphite generates nuclei on bubbles and fills them (mainly in the way of screw dislocation) forming the complete nuclei of nodular graphite-graphite bubble nuclei. Then, graphite grows up in the way of screw dislocation. Two important conditions concerning the production of nodular graphite are: (a) there is a relatively big interfacial energy between ferro liquid and graphite, and the one between ferro liquid and graphite prismatic plane is bigger than that between ferro liquid and graphite basal plane; (b) there are a certain amount of micro-bubbles in the melt.

  7. Automated, Multiplexed Electrical Impedance Spectroscopy Platform for Continuous Monitoring of Microtissue Spheroids.

    Science.gov (United States)

    Bürgel, Sebastian C; Diener, Laurin; Frey, Olivier; Kim, Jin-Young; Hierlemann, Andreas

    2016-11-15

    Microtissue spheroids in microfluidic devices are increasingly used to establish novel in vitro organ models of the human body. As the spheroids are comparably sizable, it is difficult to monitor larger numbers of them by optical means. Therefore, electrical impedance spectroscopy (EIS) emerges as a viable alternative to probing spheroid properties. Current spheroid EIS systems are, however, not suitable for investigating multiple spheroids in parallel over extended time in an automated fashion. Here we address this issue by presenting an automated, multiplexed EIS (AMEIS) platform for impedance analysis in a microfluidic setting. The system was used to continuously monitor the effect of the anticancer drug fluorouracil (5-FU) on HCT116 cancer spheroids. Simultaneous EIS monitoring of up to 15 spheroids was performed in parallel over 4 days at a temporal resolution of 2 min without any need for pumps. The measurements were continuous in nature, and the setup was kept in a standard incubator under controlled conditions during the measurements. A baseline normalization method to improve robustness and to reduce the influence of slow changes in the medium conductivity on the spheroid EIS readings has been developed and validated by experiments and means of a finite-element model. The same method and platform was then used for online monitoring of cardiac spheroids. The beating frequency of each cardiac spheroid could be read out in a completely automated fashion. The developed system constitutes a promising method for simultaneously evaluating drug impact and/or toxic effects on multiple microtissue spheroids.

  8. Reproducibility of Uniform Spheroid Formation in 384-Well Plates: The Effect of Medium Evaporation.

    Science.gov (United States)

    Das, Viswanath; Fürst, Tomáš; Gurská, Soňa; Džubák, Petr; Hajdúch, Marián

    2016-10-01

    Spheroid cultures of cancer cells reproduce the spatial dimension-induced in vivo tumor traits more effectively than the conventional two-dimensional cell cultures. With growing interest in spheroids for high-throughput screening (HTS) assays, there is an increasing demand for cost-effective miniaturization of reproducible spheroids in microtiter plates (MPs). However, well-to-well variability in spheroid size, shape, and growth is a frequently encountered problem with almost every culture method that has prevented the transfer of spheroids to the HTS platform. This variability partly arises due to increased susceptibility of MPs to edge effects and evaporation-induced changes in the growth of spheroids. In this study, we examined the effect of evaporation on the reproducibility of spheroids of tumor and nontumor cell lines in 384-well plates, and show that culture conditions that prevent evaporation-induced medium loss result in the formation of uniform spheroids across the plate. Additionally, we also present a few technical improvements to increase the scalability of the liquid-overlay spheroid culturing technique in MPs, together with a simple software routine for the quantification of spheroid size. We believe that these cost-effective improvements will aid in further improvement of spheroid cultures for HTS drug discovery.

  9. Intercalated hybrid graphite fiber composite

    Science.gov (United States)

    Gaier, James R. (Inventor)

    1993-01-01

    The invention is directed to a highly conductive lightweight hybrid material and methods of producing the same. The hybrid composite is obtained by weaving strands of a high strength carbon or graphite fiber into a fabric-like structure, depositing a layer of carbon onto the structure, heat treating the structure to graphitize the carbon layer, and intercalating the graphitic carbon layer structure. A laminate composite material useful for protection against lightning strikes comprises at least one layer of the hybrid material over at least one layer of high strength carbon or graphite fibers. The composite material of the present invention is compatible with matrix compounds, has a coefficient of thermal expansion which is the same as underlying fiber layers, and is resistant to galvanic corrosion in addition to being highly conductive. These materials are useful in the aerospace industry, in particular as lightning strike protection for airplanes.

  10. Titanium Carbide-Graphite Composites

    Science.gov (United States)

    1991-11-08

    titanium carbide , titanium carbide with free graphite, titanium carbide /vanadium carbide alloy with free graphite, and titanium carbide with...from melts. The test pins were drawn across hot pressed titanium carbide wear plates with 5 newtons of normal force. The lowest friction coefficient at...22 C was 0.12 obtained with pure titanium carbide . The lowest friction coefficient at 900 C was 0.19 obtained with titanium carbide with boron and

  11. Application of austempered ductile iron for lightening the automotive chassis%高性能球墨铸铁在汽车底盘轻量化中的应用

    Institute of Scientific and Technical Information of China (English)

    吴华锋; 张金根

    2012-01-01

    Development and excellent performance of austempered ductile iron were introduced. Application trends and conditions of austempered ductile iron for the auto classis were analyzed in order, to lighten its weight. And finally, the austempered ductile iron application in practical production were introduced.%介绍了高性能球墨铸铁的发展现状及优异性能,并结合汽车轻量化需求,分析了等温淬火球墨铸铁材料在汽车底盘上的应用趋势,最后介绍了等温淬火球墨铸铁在实际生产中的应用。

  12. Effects of temperature on internal friction of Graphit-iC graphite-like carbon coatings

    Science.gov (United States)

    Zhu, Zhi-yong; Shi, Wen; Wan, Zi; Yuan, Jun-feng; Li, Xiao

    2013-12-01

    Graphit-iC graphite-like carbon coatings were deposited on SDC90 cold work die steel by using an unbalanced magnetron sputtering technology. Effects of the temperature on microstructure and internal friction of the carbon coatings were characterized by Raman spectroscopy (Raman) and a low-frequency mechanical analyzer (LMA-1) testing system. The results indicate that the internal friction of the two-side deposited carbon coatings is small (2.17×10-4), being higher than one of the substrate (1.63×10-4), and increases with temperature. However, there is an internal friction peak at 250°C accompanied with partial sp3 transferred to sp2 and increasing the intensity ratio ID/IG. There is gradual graphitization tendency of the carbon coatings as temperatures increase from 25°C to 350 °C. This would be progressive transformation from amorphous to crystalline.

  13. Binding and interstitial penetration of liposomes within avascular tumor spheroids.

    Science.gov (United States)

    Kostarelos, Kostas; Emfietzoglou, Dimitris; Papakostas, Alexandros; Yang, Wei-Hong; Ballangrud, Ase; Sgouros, George

    2004-11-20

    The liposomal delivery of cancer therapeutics, including gene therapy vectors, is an area of intense study. Poor penetration of liposomes into interstitial tumor spaces remains a problem, however. In this work, the penetration of different liposomal formulations into prostate carcinoma spheroids was examined. Spheroid penetration was assessed by confocal microscopy of fluorescently labeled liposomes. The impact of liposomal surface charge, mean diameter, lipid bilayer fluidity and fusogenicity on spheroid penetration was examined. A variety of different liposome systems relevant to clinical or preclinical protocols have been studied, including classical zwitterionic (DMPC:chol) and sterically stabilized liposomes (DMPC:chol:DOPE-PEG2000), both used clinically, and cationic liposomes (DMPC:DOPE:DC-chol and DOTAP), forming the basis of the vast majority of nonviral gene transfer vectors tested in various cancer trials. Surface interactions between strongly cationic vesicles and the tumor cells led to an electrostatically derived binding-site barrier effect, inhibiting further association of the delivery systems with the tumor spheroids (DMPC:DC-chol). However, inclusion of the fusogenic lipid DOPE and use of a cationic lipid of lower surface charge density (DOTAP instead of DC-chol) led to improvements in the observed intratumoral distribution characteristics. Sterically stabilized liposomes did not interact with the tumor spheroids, whereas small unilamellar classical liposomes exhibit extensive distribution deeper into the tumor volume. Engineering liposomal delivery systems with a relatively low charge molar ratio and enhanced fusogenicity, or electrostatically neutral liposomes with fluid bilayers, offered enhanced intratumoral penetration. This study shows that a delicate balance exists between the strong affinity of delivery systems for the tumor cells and the efficient penetration and distribution within the tumor mass, similar to previous work studying

  14. Tethered spheroids as an in vitro hepatocyte model for drug safety screening.

    Science.gov (United States)

    Xia, Lei; Sakban, Rashidah Binte; Qu, Yinghua; Hong, Xin; Zhang, Wenxia; Nugraha, Bramasta; Tong, Wen Hao; Ananthanarayanan, Abhishek; Zheng, Baixue; Chau, Ian Yin-Yan; Jia, Ruirui; McMillian, Michael; Silva, Jose; Dallas, Shannon; Yu, Hanry

    2012-03-01

    Hepatocyte spheroids mimic many in vivo liver-tissue phenotypes but increase in size during extended culture which limits their application in drug testing applications. We have developed an improved hepatocyte 3D spheroid model, namely tethered spheroids, on RGD and galactose-conjugated membranes using an optimized hybrid ratio of the two bioactive ligands. Cells in the spheroid configuration maintained 3D morphology and uncompromised differentiated hepatocyte functions (urea and albumin production), while the spheroid bottom was firmly tethered to the substratum maintaining the spheroid size in multi-well plates. The oblate shape of the tethered spheroids, with an average height of 32 μm, ensured efficient nutrient, oxygen and drug access to all the cells within the spheroid structure. Cytochrome P450 induction by prototypical inducers was demonstrated in the tethered spheroids and was comparable or better than that observed with hepatocyte sandwich cultures. These data suggested that tethered 3D hepatocyte spheroids may be an excellent alternative to 2D hepatocyte culture models for drug safety applications.

  15. Isothermal Quenching Temperature and Time on Microstructure and Mechanical Properties Effect of Austempered Ductile Iron%等温淬火温度和时间对奥贝球铁组织性能的影响

    Institute of Scientific and Technical Information of China (English)

    吴秋敏; 袁延彬; 李广路

    2012-01-01

    本文通过工艺试验,介绍了奥贝球铁在等温淬火的不同温度下的变化情况及对其切削性能的影响。给出了最佳等温淬火温度和时间。%This article, through process test. introduced changing conditions and its cutting performance of austempered ductile iron in the isothermal quenching ureter different temperatures, giving the optimal austempering temperature and time.

  16. Mass transfer inside oblate spheroidal solids: modelling and simulation

    Directory of Open Access Journals (Sweden)

    J. E. F. Carmo

    2008-03-01

    Full Text Available A numerical solution of the unsteady diffusion equation describing mass transfer inside oblate spheroids, considering a constant diffusion coefficient and the convective boundary condition, is presented. The diffusion equation written in the oblate spheroidal coordinate system was used for a two-dimensional case. The finite-volume method was employed to discretize the basic equation. The linear equation set was solved iteratively using the Gauss-Seidel method. As applications, the effects of the Fourier number, the Biot number and the aspect ratio of the body on the drying rate and moisture content during the process are presented. To validate the methodology, results obtained in this work are compared with analytical results of the moisture content encountered in the literature and good agreement was obtained. The results show that the model is consistent and it may be used to solve cases such as those that include disks and spheres and/or those with variable properties with small modifications.

  17. A method of smoothed particle hydrodynamics using spheroidal kernels

    Science.gov (United States)

    Fulbright, Michael S.; Benz, Willy; Davies, Melvyn B.

    1995-01-01

    We present a new method of three-dimensional smoothed particle hydrodynamics (SPH) designed to model systems dominated by deformation along a preferential axis. These systems cause severe problems for SPH codes using spherical kernels, which are best suited for modeling systems which retain rough spherical symmetry. Our method allows the smoothing length in the direction of the deformation to evolve independently of the smoothing length in the perpendicular plane, resulting in a kernel with a spheroidal shape. As a result the spatial resolution in the direction of deformation is significantly improved. As a test case we present the one-dimensional homologous collapse of a zero-temperature, uniform-density cloud, which serves to demonstrate the advantages of spheroidal kernels. We also present new results on the problem of the tidal disruption of a star by a massive black hole.

  18. Plasma spheroidization of nickel powders in a plasma reactor

    Indian Academy of Sciences (India)

    G Shanmugavelayutham; V Selvarajan

    2004-10-01

    Thermal spray coatings of surfaces with metal, alloy and ceramic materials for protection against corrosion, erosion and wear is an intense field of research. The technique involves injection of the powder into a plasma flame, melting, acceleration of the powder particles, impact and bonding with the substrate. Feedstock powders of metals, alloys and ceramics for thermal spray applications have to meet several requirements. Particle shape, size and its distribution, powder flow characteristics and density are the important factors to be considered in order to ensure high spray efficiency and better coating properties. For smooth and uniform feeding of powders into plasma jet, the powder particles have to be spherical in shape. High temperatures and steep temperatures present in thermal plasma is exploited to spheroidize particles in the present investigation. Nickel powder particles in the size range from 40–100 m were spheroidized using plasma processing. SEM and optical micrographs showed spherical shape of processed particles.

  19. Dwarf spheroidal galaxies and Bose-Einstein condensate dark matter

    CERN Document Server

    Diez-Tejedor, Alberto; Profumo, Stefano

    2014-01-01

    We constrain the parameters of a self-interacting massive dark matter scalar particle in a condensate using the kinematics of the eight brightest dwarf spheroidal satellites of the Milky Way. For the case of an attractive self-interaction the condensate develops a mass density profile with a characteristic scale radius that is closely related to the fundamental parameters of the theory. We find that the velocity dispersion of dwarf spheroidal galaxies suggests a scale radius of the order of 1 kpc, in tension with previous results found using the rotational curve of low-surface-brightness and dwarf galaxies. We discuss the implications of our findings for the particle dark matter model and argue that a single classical coherent state cannot play, in general, a relevant role for the description of dark matter in galaxies.

  20. A VIRIAL CORE IN THE SCULPTOR DWARF SPHEROIDAL GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Agnello, A.; Evans, N. W., E-mail: aagnello@ast.cam.ac.uk, E-mail: nwe@ast.cam.ac.uk [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2012-08-01

    The projected virial theorem is applied to the case of multiple stellar populations in the nearby dwarf spheroidal galaxies. As each population must reside in the same gravitational potential, this provides strong constraints on the nature of the dark matter halo. We derive necessary conditions for two populations with Plummer or exponential surface brightnesses to reside in a cusped Navarro-Frenk-White (NFW) halo. We apply our methods to the Sculptor dwarf spheroidal, and show that there is no NFW halo compatible with the energetics of the two populations. The dark halo must possess a core radius of {approx}120 pc for the virial solutions for the two populations to be consistent. This conclusion remains true, even if the effects of flattening or self-gravity of the stellar populations are included.

  1. Scaffold-free Prevascularized Microtissue Spheroids for Pulp Regeneration.

    Science.gov (United States)

    Dissanayaka, W L; Zhu, L; Hargreaves, K M; Jin, L; Zhang, C

    2014-12-01

    Creating an optimal microenvironment that mimics the extracellular matrix (ECM) of natural pulp and securing an adequate blood supply for the survival of cell transplants are major hurdles that need to be overcome in dental pulp regeneration. However, many currently available scaffolds fail to mimic essential functions of natural ECM. The present study investigated a novel approach involving the use of scaffold-free microtissue spheroids of dental pulp stem cells (DPSCs) prevascularized by human umbilical vein endothelial cells (HUVECs) in pulp regeneration. In vitro-fabricated microtissue spheroids were inserted into the canal space of tooth-root slices and were implanted subcutaneously into immunodeficient mice. Histological examination revealed that, after four-week implantation, tooth-root slices containing microtissue spheroids resulted in well-vascularized and cellular pulp-like tissues, compared with empty tooth-root slices, which were filled with only subcutaneous fat tissue. Immunohistochemical staining indicated that the tissue found in the tooth-root slices was of human origin, as characterized by the expression of human mitochondria, and contained odontoblast-like cells organized along the dentin, as assessed by immunostaining for nestin and dentin sialoprotein (DSP). Vascular structures formed by HUVECs in vitro were successfully anastomosed with the host vasculature upon transplantation in vivo, as shown by immunostaining for human CD31. Collectively, these findings demonstrate that prevascularized, scaffold-free, microtissue spheroids can successfully regenerate vascular dental pulp-like tissue and also highlight the significance of the microtissue microenvironment as an optimal environment for successful pulp-regeneration strategies. © International & American Associations for Dental Research.

  2. VERITAS Deep Observations of the Dwarf Spheroidal Galaxy Segue 1

    CERN Document Server

    Aliu, E; Arlen, T; Aune, T; Beilicke, M; Benbow, W; Bouvier, A; Bradbury, S M; Buckley, J H; Bugaev, V; Byrum, K; Cannon, A; Cesarini, A; Christiansen, J L; Ciupik, L; Collins-Hughes, E; Connolly, M P; Cui, W; Decerprit, G; Dickherber, R; Dumm, J; Errando, M; Falcone, A; Feng, Q; Ferrer, F; Finley, J P; Finnegan, G; Fortson, L; Furniss, A; Galante, N; Gall, D; Godambe, S; Griffin, S; Grube, J; Gyuk, G; Hanna, D; Holder, J; Huan, H; Hughes, G; Humensky, T B; Kaaret, P; Karlsson, N; Kertzman, M; Khassen, Y; Kieda, D; Krawczynski, H; Krennrich, F; Lee, K; Madhavan, A S; Maier, G; Majumdar, P; McArthur, S; McCann, A; Moriarty, P; Mukherjee, R; Ong, R A; Orr, M; Otte, A N; Park, N; Perkins, J S; Pohl, M; Prokoph, H; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Rose, H J; Ruppel, J; Saxon, D B; Schroedter, M; Sembroski, G H; Senturk, G D; Skole, C; Smith, A W; Staszak, D; Telezhinsky, I; Tesic, G; Theiling, M; Thibadeau, S; Tsurusaki, K; Varlotta, A; Vassiliev, V V; Vincent, S; Vivier, M; Wagner, R G; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; Weisgarber, T; Williams, D A; Zitzer, B

    2012-01-01

    The VERITAS array of Cherenkov telescopes has carried out a deep observational program on the nearby dwarf spheroidal galaxy Segue 1. We report on the results of nearly 48 hours of good quality selected data, taken between January 2010 and May 2011. No significant $\\gamma$-ray emission is detected at the nominal position of Segue 1, and upper limits on the integrated flux are derived. According to recent studies, Segue 1 is the most dark matter-dominated dwarf spheroidal galaxy currently known. We derive stringent bounds on various annihilating and decaying dark matter particle models. The upper limits on the velocity-weighted annihilation cross-section are $\\mathrm{^{95% CL} \\lesssim 10^{-23} cm^{3} s^{-1}}$, improving our limits from previous observations of dwarf spheroidal galaxies by at least a factor of two for dark matter particle masses $\\mathrm{m_{\\chi}\\gtrsim 300 GeV}$. The lower limits on the decay lifetime are at the level of $\\mathrm{\\tau^{95% CL} \\gtrsim 10^{24} s}$. Finally, we address the inte...

  3. Reparative Spheroids in HPV-Associated Chronic Cervicitis

    Directory of Open Access Journals (Sweden)

    Gennadiy T. Sukhikh

    2013-09-01

    Full Text Available Background: Spheroid cell structures (SCS described in cell culture are used to study cell-cell and cell-matrix interactions. However, the role of the SCS in the repair process in vivo remains unexplored. The aim of the study was to examine the cellular composition of the spherical structures and their functional significance in the repair of the squamous epithelium in human papilloma virus-associated chronic cervicitis (HPV-CC. Methods and Results: The cytology and biopsy materials from 223 patients with HPV-CC were subjected to molecular testing for HPV DNA by Real-Time Polymerase Chain Reaction (Real-Time PCR with genotyping and chromogenic in situ hybridization (CISH, as well as immunocytological and immunohistochemical analyses of p16INK4A, Ki67, SMA, Vimentin, CD34, E-cadherin, Oct4, CD44, CKW markers. In the stem cell niche zone, these spheroid structures were discovered having proliferative activity and showing signs of producing stem cells involved in the repair of the cervical mucosa in HPV-CC. Conclusion: The persistence of the HPV in the stem cell niche zone cells in the cervix determines the chronization of inflammation in this area, with the ability to perform pathological repair. The immunophenotype of the spheroid cell structures in the HPV-CC includes cells with signs of stem cells (‘stemness’ and the mesenchymal-epithelial transition.

  4. Silicon spheroidization treatment of thixoformed Al-Si-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ogris, E.; Uggowitzer, P.J. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. of Metallurgy; Luechinger, H. [SAG-Aluminium Lend GmbH und Co KG and THIXALLOY trademark Components GmbH und Co KG, Lend (Austria)

    2002-07-01

    Al-Si-Mg alloys are commonly used in the automobile industry because of their outstanding mechanical properties and corrosion resistance. The need of lighter and safer cars is the driving force behind research in the area of high strength light metal safety part applications. The strength level can be tuned by varying the amount of alloyed magnesium. Usually if strength is increased, ductility will decrease. Following the demands of the automotive industry, safety parts should have a minimum fracture elongation of 15% and a minimum yield strength of 150 MPa. The huge hurdle is the 15% fracture elongation which can not be reached by sand or die casting, but some relatively new alternative casting technologies, like Thioxocasting or New Rheocasting, yield encouraging ductility values. Recent research activity has focused on increasing strength and ductility, but so far the results have not yet been satisfying. This paper presents investigations on the spheroidization process of eutectic silicon and its positive effect on mechanical properties. It is shown that the spheroidization process is already finished after minutes of exposure to heat treatment. Metallographical and quantitative microstructural analysis is used to describe the growth and spheroidization process of the silicon crystals. Specimens of THIXALLOY trademark 630 (A356) thixocast components were heat treated for varied periods of time, aged and tested. Results show amazing improvements of ductility and strength in comparison to the as cast state. Maximum values of 18% fracture elongation and 230 MPa yield strength are reached. (orig.)

  5. Vibration of fluid-loaded hemi-prolate spheroidal shells

    Science.gov (United States)

    Boisvert, Jeffrey E.; Hayek, Sabih I.

    2003-04-01

    The equations of motion for nonaxisymmetric vibration of hemi-prolate spheroidal shells of constant thickness were derived using Hamilton's principle. The shell is clamped at the equator and is excited by mechanical surface force fields. The shell theory used in this derivation includes shear deformations and rotatory inertias. The displacements and rotations were expanded in an infinite series of comparison functions. The shell is fluid-filled and is submerged in an infinite fluid medium. The external and internal fluid loading impedances were computed using expansions of prolate spheroidal wavefunctions in each domain. The dynamic response of the fluid-loaded shell was determined using an axisymmetric normal surface force as the excitation input. Numerical results were obtained for the driving and transfer mobilities for several shell thickness-to-length ratios ranging from 0.005 to 0.1, and for various shape parameters, ``a,'' ranging from an elongated hemi-spheroidal shell (a=1.01) to a hemispherical shell (a=100). Results are presented for various combinations of external and internal fluid loading, and comparisons are made to the in-vacuo shell vibration. [Work supported by ONR and the Navy/ASEE Summer Faculty Program.

  6. Formation mechanism of spheroidal carbide in ultra-low carbon ductile cast iron

    Directory of Open Access Journals (Sweden)

    Bin-guo Fu

    2016-09-01

    Full Text Available The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal carbide belonged to eutectic carbide and crystallized in the isolated eutectic liquid phase area. The formation process of the spheroidal carbide was related to the contact and the intersection between the primary dendrite and the secondary dendrite of austenite. The oxides of magnesium, rare earths and other elements can act as heterogeneous nucleation sites for the spheroidal carbide. It was also found that the amount of the spheroidal carbide would increase with an increase in carbon content. The cooling rate has an important influence on the spheroidal carbide under the same chemical composition condition.

  7. Thermal Pyrolytic Graphite Enhanced Components

    Science.gov (United States)

    Hardesty, Robert E. (Inventor)

    2015-01-01

    A thermally conductive composite material, a thermal transfer device made of the material, and a method for making the material are disclosed. Apertures or depressions are formed in aluminum or aluminum alloy. Plugs are formed of thermal pyrolytic graphite. An amount of silicon sufficient for liquid interface diffusion bonding is applied, for example by vapor deposition or use of aluminum silicon alloy foil. The plugs are inserted in the apertures or depressions. Bonding energy is applied, for example by applying pressure and heat using a hot isostatic press. The thermal pyrolytic graphite, aluminum or aluminum alloy and silicon form a eutectic alloy. As a result, the plugs are bonded into the apertures or depressions. The composite material can be machined to produce finished devices such as the thermal transfer device. Thermally conductive planes of the thermal pyrolytic graphite plugs may be aligned in parallel to present a thermal conduction path.

  8. Friction anisotropy in boronated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, N., E-mail: niranjan@igcar.gov.in [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Radhika, R. [Crystal Growth Centre, Anna University, Chennai (India); Kozakov, A.T. [Research Institute of Physics, Southern Federal University, Rostov-on-Don (Russian Federation); Pandian, R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Chakravarty, S. [UGC-DAE CSR, Kalpakkam (India); Ravindran, T.R.; Dash, S.; Tyagi, A.K. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    2015-01-01

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

  9. Influence of molding sand on the number of grains graphite and on the rate of thin ferrite in pieces in a nodular iron ferritic matrix

    Directory of Open Access Journals (Sweden)

    B. Khatemi

    2010-07-01

    Full Text Available The nodular cast irons are characterized by high mechanical properties compared to cast iron with lamellar graphite or vermiculargraphite. The ductile iron has already been the subject of many studies especially since the literature is rich on them, and sources of information are different. The fact is that the mechanical properties of nodular cast iron (FGS depend on the number of graphitegrains, their roundness, the solidification rate and nature of the matrix [3]. Many studies of nodular cast irons showed that the morespherical particles of graphite, the higher the mechanical properties are high. In gray cast irons, the graphite spheroids have anticrackingand give the ductile iron ductility. Note in this connection that the higher the number of graphite grains, the higher theductile iron has better mechanical properties. In cast iron, the nature of the matrix is depending on several parameters including thecooling rate of molten metal, the thickness, shape and dimensions of parts. The faster cooling is slow over rate of ferrite is important[3, 4]. In this paper, we tested three types of sand casting: sand –based sodium silicate, furan resin and green sand on samplesspherical graphite cast iron of different thickness. The objective in this article is to determine the number of grains of graphite andferrite for each type of sand casting under the same experimental conditions including the cooling rate and chemical composition ofthe liquid metal.

  10. Method of Joining Graphite Fibers to a Substrate

    Science.gov (United States)

    Beringer, Durwood M. (Inventor); Caron, Mark E. (Inventor); Taddey, Edmund P. (Inventor); Gleason, Brian P. (Inventor)

    2014-01-01

    A method of assembling a metallic-graphite structure includes forming a wetted graphite subassembly by arranging one or more layers of graphite fiber material including a plurality of graphite fibers and applying a layer of metallization material to ends of the plurality of graphite fibers. At least one metallic substrate is secured to the wetted graphite subassembly via the layer of metallization material.

  11. Fluid absorption related to ion transport in human airway epithelial spheroids

    DEFF Research Database (Denmark)

    Pedersen, P S; Holstein-Rathlou, N H; Larsen, P L

    1999-01-01

    , and amiloride inhibited both values. Fluid transport rates were calculated from repeated measurements of spheroid diameters. The results showed that 1) non-CF and CF spheroids absorbed fluid at identical rates (4.4 microl x cm(-2) x h(-1)), 2) amiloride inhibited fluid absorption to a lower residual level......) osmotic water permeabilities were equal in non-CF and CF spheroids ( approximately 27 x 10(-7) cm x s(-1) x atm(-1))....

  12. Multiparametric Analysis of Oncology Drug Screening with Aqueous Two-Phase Tumor Spheroids.

    Science.gov (United States)

    Shahi Thakuri, Pradip; Ham, Stephanie L; Luker, Gary D; Tavana, Hossein

    2016-11-07

    Spheroids present a biologically relevant three-dimensional model of avascular tumors and a unique tool for discovery of anticancer drugs. Despite being used in research laboratories for several decades, spheroids are not routinely used in the mainstream drug discovery pipeline primarily due to the difficulty of mass-producing uniformly sized spheroids and intense labor involved in handling, drug treatment, and analyzing spheroids. We overcome this barrier using a polymeric aqueous two-phase microtechnology to robotically microprint spheroids of well-defined size in standard 384-microwell plates. We use different cancer cells and show that resulting spheroids grow over time and display characteristic features of solid tumors. We demonstrate the feasibility of robotic, high-throughput screening of 25 standard chemotherapeutics and molecular inhibitors against tumor spheroids of three different cancer cell lines. This screening uses over 7000 spheroids to elicit high quality dose-dependent drug responses from spheroids. To quantitatively compare performance of different drugs, we employ a multiparametric scoring system using half-maximum inhibitory concentration (IC50), maximum inhibition (Emax), and area under the dose-response curve (AUC) to take into account both potency and efficacy parameters. This approach allows us to identify several compounds that effectively inhibit growth of spheroids and compromise cellular viability, and distinguish them from moderately effective and ineffective drugs. Using protein expression analysis, we demonstrate that spheroids generated with the aqueous two-phase microtechnology reliably resolve molecular targets of drug compounds. Incorporating this low-cost and convenient-to-use tumor spheroid technology in preclinical drug discovery will make compound screening with realistic tumor models a routine laboratory technique prior to expensive and tedious animal tests to dramatically improve testing throughput and efficiency and

  13. Raman characterization of bulk ferromagnetic nanostructured graphite

    Energy Technology Data Exchange (ETDEWEB)

    Pardo, Helena, E-mail: hpardo@fq.edu.uy [Centro NanoMat, Polo Tecnologico de Pando, Facultad de Quimica, Universidad de la Republica, Cno. Aparicio Saravia s/n, 91000, Pando, Canelones (Uruguay); Crystallography, Solid State and Materials Laboratory (Cryssmat-Lab), DETEMA, Facultad de Quimica, Universidad de la Republica, Gral. Flores 2124, P.O. Box 1157, Montevideo (Uruguay); Divine Khan, Ngwashi [Mantfort University, Leicester (United Kingdom); Faccio, Ricardo [Centro NanoMat, Polo Tecnologico de Pando, Facultad de Quimica, Universidad de la Republica, Cno. Aparicio Saravia s/n, 91000, Pando, Canelones (Uruguay); Crystallography, Solid State and Materials Laboratory (Cryssmat-Lab), DETEMA, Facultad de Quimica, Universidad de la Republica, Gral. Flores 2124, P.O. Box 1157, Montevideo (Uruguay); Araujo-Moreira, F.M. [Grupo de Materiais e Dispositivos-CMDMC, Departamento de Fisica e Engenharia Fisica, UFSCar, Caixa Postal 676, 13565-905, Sao Carlos SP (Brazil); Fernandez-Werner, Luciana [Centro NanoMat, Polo Tecnologico de Pando, Facultad de Quimica, Universidad de la Republica, Cno. Aparicio Saravia s/n, 91000, Pando, Canelones (Uruguay); Crystallography, Solid State and Materials Laboratory (Cryssmat-Lab), DETEMA, Facultad de Quimica, Universidad de la Republica, Gral. Flores 2124, P.O. Box 1157, Montevideo (Uruguay)

    2012-08-15

    Raman spectroscopy was used to characterize bulk ferromagnetic graphite samples prepared by controlled oxidation of commercial pristine graphite powder. The G:D band intensity ratio, the shape and position of the 2D band and the presence of a band around 2950 cm{sup -1} showed a high degree of disorder in the modified graphite sample, with a significant presence of exposed edges of graphitic planes as well as a high degree of attached hydrogen atoms.

  14. Fabrication of Graphene by Cleaving Graphite Chemically

    Institute of Scientific and Technical Information of China (English)

    ZHAO Shu-hua; ZHAO Xiao-ting; FAN Hou-gang; YANG Li-li; ZHANG Yong-jun; YANG Jing-hai

    2011-01-01

    Graphite was chemically cleaved to graphene by Billups Reaction,and the morphologies and microstructures of graphene were characterized by SEM,Raman and AFM.The results show that the graphite was first functionalized by l-iodododecane,which led to the cleavage of the graphene layer in the graphite.The second decoration cleaved the graphite further and graphene was obtained.The heights of the graphene layer were larger than 1 nm due to the organic decoration.

  15. Experiments on Graphitization of Diamond in the Presence of Water: Implications for Exhumation of Ultrahigh Pressure Metamorphic Rocks

    Science.gov (United States)

    O'Bannon, E. F.; Xia, G.; Green, H. W.; Wirth, R.; Dobrzhinetskaya, L.

    2012-12-01

    Diamond and graphite occur in the mantle, and crustal ultrahigh pressure metamorphic (UHPM) rocks. The stability fields of carbon are well studied experimentally, but the mechanisms of phase transformation are not well understood. Observations on natural samples from UHPM terranes show that graphitization of diamond is accompanied by the formation of disordered graphite containing nanometric fluid inclusions. Since the structures of diamond and graphite are very dissimilar, it is unlikely that a direct phase transformation would occur during the graphitization process. Such an assumption is also supported by higher enthalpy (1.897) and lower entropy (2.38) of C-diamond with respect of those of C-graphite (enthalpy = 0, entropy=5.74). At least three different mechanisms of diamond-to-graphite transformation have been proposed. To constrain this process we conducted a series of anhydrous and hydrous experiments in a piston-cylinder apparatus and a hydrous experiment in a multianvil apparatus using 20-40 micron size virgin diamonds as the starting material. The piston-cylinder experiments were conducted at P=1 GPa and T=1300oC. In the hydrous experiments 1.15 wt.%. Mg(OH)2 was added to the starting material as the H2O supply according to the breakdown reaction: Mg(OH)2 = MgO + H2O. The multianvil experiment was conducted at P=6GPa and T=1300oC with 1 wt.%. distilled water added to the starting diamonds. Run products were studied with SEM, FIB assisted TEM, and SEM-Raman. The anhydrous experiments show that diamond crystals are "integrated" together producing deformed polycrystallites with complicated textural patterns occurring at the grain boundaries. The hydrous experiments show the formation of metastable nanometric spheroidal carbon particles which were distributed on the surface and between the corners of the diamonds. The metastable phase existed for ~6 months before it decomposed into graphite flakes. The graphite flakes have a disordered structure which was

  16. Microstructures and Mechanical Properties of Helical Bevel Gears Made by Mn-Cu Alloyed Austempered Ductile Iron

    Institute of Scientific and Technical Information of China (English)

    LIU Sheng-fa; CHEN Yang; CHEN Xin; MIAO Hua-ming

    2012-01-01

    Austempered ductile iron (ADI) has several advantages of replacing cast steel and forged steel in many engineering fields. A new Mn-Cu alloyed ADI with excellent mechanical properties has been developed in order to cut the cost and enlarge the application of ADI. The helical bevel gears were made of the new-developed Mn-Cu alloyed ADI. The microstructure and mechanical properties of the standard sample were investigated by optical microscope (OM), scanning electron microscope (SEM) and performance measurement. The results showed that after a series of treatments, the mechanical properties (Rm 1007. 4 to 1200 MPa, A 5.2% to 8. 8%, HRC 32 to HRC 35, O~K 70 to 120 J/cmz ) of the Mn-Cu alloyed ADI standard sample could reach European standard EN1564-97/ EN-CJS-1000-5. The surface hardness after helical bevel gears meshing was significantly increased due to the formation of martensite. The bench test and traffic running testing results suggested that the new Mn-Cu alloyed ADI with ultimate life and median life respectively exceeding 30×104 and 50 × 10^4 times could replace 20CrMnTi forged steel for manufacturing the EQ140 helical bevel gears.

  17. Corrosion behaviour and structure of the surface layer formed on austempered ductile iron in concentrated sulphuric acid

    Energy Technology Data Exchange (ETDEWEB)

    Krawiec, H. [AGH University of Science and Technology, Department of Foundry Engineering, ul. Reymonta 23, 30-059 Cracow (Poland)]. E-mail: krawiec@uci.agh.edu.pl; Stypula, B. [AGH University of Science and Technology, Department of Foundry Engineering, ul. Reymonta 23, 30-059 Cracow (Poland); Stoch, J. [Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (PAS), ul. Niezapominajek 8, 30-239 Cracow (Poland); Mikolajczyk, M. [Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (PAS), ul. Niezapominajek 8, 30-239 Cracow (Poland)

    2006-03-15

    The aim of this paper is to investigate the structure of the surface layer formed on austempered ductile iron (ADI) after exposure to hot concentrated sulphuric acid at the open circuit potential value (OCP). The results derived from polarization measurements carried out in sulphuric acid at a temperature of 90 deg. C show that anodic dissolution of ADI is divided into three stages (corresponding to three anodic dissolution peaks). The structure of the layer formed on alloys at 90 deg. C at OCP was investigated using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). SEM analysis shows that the main elements of the surface layer are iron, silicon, oxygen, sulphur, and carbon. The binding energy recorded in individual bands indicates that the surface layer includes mainly SiO{sub 2} and FeOOH. The presence of sulphur at the lower oxidation state (S{sup 2-}) indicates that sulphuric acid undergoes reduction during this process. The corrosion resistance of these alloys is connected with the presence of SiO{sub 2} in the surface layer.

  18. Microstructure and Mechanical Properties of 50SiMnNiNb Steel by a Novel Quenching-Partitioning-Austempering Heat Treatment

    Institute of Scientific and Technical Information of China (English)

    LI Hongyan; JIN Xuejun

    2009-01-01

    For the purpose of reducing weight of steel parts, save raw materials and keep or even improve safety standards, the development of advanced high strength steels is increasingly demanded in the automotive industry and engineering applications. We have proposed a novel heat treatment (quenching-partitioning-austempering treatment, Q-P-A) to obtain steel parts with high strength and good ductility. The Q-P-A process is intended to produce microstructure consisted of carbon-depleted martensite, carbon-enriched retained austenite and nanostructured bainite. Quenching(Q) treatment fabricates mixed microstructure of carbon-supersaturated martensite and certain amounts of untransformed austenite. Partitioning(P) thermal treatment accomplishes fully diffusing of carbon from the supersaturated martensite phase to the untransformed austenite phase and enriching the amount of carbon in untransformed austenite. Further low-temperature austempering(A) process induces incredible thin bainite from the carbon-enriched untransformed austenite. A study of the microstructure and mechanical properties of 50SiMnNiNb steel subjected to the novel Q-P-A treatment is presented. Microstructure is assessed by optical microscope(OM), field emission scanning electron microscope(FESEM) and transmission electron microscope(TEM), and the corresponding mechanical properties are measured. The experimental results indicate that attractive mechanical properties of steels during the Q-P-A process are attributed to the complex multi-phase structure. Slender plates of bainite with 20-40 nm thick are generated in the medium carbon steel. Meanwhile, with increasing of the volume fraction of nanostructured bainite, yield strength of steel parts is increased with little degradation of ultimate tensile strength. In this paper, a novel quenching-partitioning-austempering heat treatment is proposed, and the attractive mechanical properties of steels are obtained during the Q-P-A process.

  19. Galaxy and Mass Assembly (GAMA): the stellar mass budget of galaxy spheroids and discs

    OpenAIRE

    Moffett, Amanda J.; Lange, Rebecca; Driver, Simon P.; Robotham, Aaron S G; Kelvin, Lee S; Alpaslan, Mehmet; Andrews, Stephen K.; Bland-Hawthorn, Joss; Brough, Sarah; Cluver, Michelle E.; Colless, Matthew; Davies, Luke J. M.; Holwerda, Benne W.; Hopkins, Andrew M; Kafle, Prajwal R.

    2016-01-01

    We build on a recent photometric decomposition analysis of 7506 Galaxy and Mass Assembly (GAMA) survey galaxies to derive stellar mass function fits to individual spheroid and disc component populations down to a lower mass limit of log(M*/M⊙) = 8. We find that the spheroid/disc mass distributions for individual galaxy morphological types are well described by single Schechter function forms. We derive estimates of the total stellar mass densities in spheroidsspheroid = 1.24 ± 0.49 × 108 M...

  20. Increased Survival and Function of Mesenchymal Stem Cell Spheroids Entrapped in Instructive Alginate Hydrogels

    Science.gov (United States)

    Ho, Steve S.; Murphy, Kaitlin C.; Binder, Bernard Y.K.; Vissers, Caroline B.

    2016-01-01

    Mesenchymal stem cell (MSC)-based therapies are under broad investigation for applications in tissue repair but suffer from poor cell persistence and engraftment upon transplantation. MSC spheroids exhibit improved survival, anti-inflammatory, and angiogenic potential in vitro, while also promoting vascularization when implanted in vivo. However, these benefits are lost once cells engage the tissue extracellular matrix and migrate from the aggregate. The efficacy of cell therapy is consistently improved when using engineered materials, motivating the need to investigate the role of biomaterials to instruct spheroid function. In order to assess the contribution of adhesivity on spheroid activity in engineered materials and promote the bone-forming potential of MSCs, we compared the function of MSC spheroids when entrapped in Arg-Gly-Asp (RGD)-modified alginate hydrogels to nonfouling unmodified alginate. Regardless of material, MSC spheroids exhibited reduced caspase activity and greater vascular endothelial growth factor (VEGF) secretion compared with equal numbers of dissociated cells. MSC spheroids in RGD-modified hydrogels demonstrated significantly greater cell survival than spheroids in unmodified alginate. After 5 days in culture, spheroids in RGD-modified gels had similar levels of apoptosis, but more than a twofold increase in VEGF secretion compared with spheroids in unmodified gels. All gels contained mineralized tissue 8 weeks after subcutaneous implantation, and cells entrapped in RGD-modified alginate exhibited greater mineralization versus cells in unmodified gels. Immunohistochemistry confirmed more diffuse osteocalcin staining in gels containing spheroids compared with dissociated controls. This study demonstrates the promise of cell-instructive biomaterials to direct survival and function of MSC spheroids for bone tissue engineering applications. Significance Mesenchymal stem cell (MSC) spheroids exhibit improved therapeutic potential in vitro

  1. Methods: Using Three-Dimensional Culture (Spheroids) as an In Vitro Model of Tumour Hypoxia.

    Science.gov (United States)

    Leek, Russell; Grimes, David Robert; Harris, Adrian L; McIntyre, Alan

    Regions of hypoxia in tumours can be modelled in vitro in 2D cell cultures with a hypoxic chamber or incubator in which oxygen levels can be regulated. Although this system is useful in many respects, it disregards the additional physiological gradients of the hypoxic microenvironment, which result in reduced nutrients and more acidic pH. Another approach to hypoxia modelling is to use three-dimensional spheroid cultures. In spheroids, the physiological gradients of the hypoxic tumour microenvironment can be inexpensively modelled and explored. In addition, spheroids offer the advantage of more representative modelling of tumour therapy responses compared with 2D culture. Here, we review the use of spheroids in hypoxia tumour biology research and highlight the different methodologies for spheroid formation and how to obtain uniformity. We explore the challenge of spheroid analyses and how to determine the effect on the hypoxic versus normoxic components of spheroids. We discuss the use of high-throughput analyses in hypoxia screening of spheroids. Furthermore, we examine the use of mathematical modelling of spheroids to understand more fully the hypoxic tumour microenvironment.

  2. Photoemission study of K on graphite

    NARCIS (Netherlands)

    Bennich, P.; Puglia, C.; Brühwiler, P.A.; Nilsson, A.; Sandell, A.; Mårtensson, N.; Rudolf, P.

    1999-01-01

    The physical and electronic structure of the dispersed and (2×2) phases of K/graphite have been characterized by valence and core-level photoemission. Charge transfer from K to graphite is found to occur at all coverages, and includes transfer of charge to the second graphite layer. A rigid band

  3. Separation medium containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Herrera-Alonso, Margarita (Inventor)

    2012-01-01

    A separation medium, such as a chromatography filling or packing, containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g, wherein the thermally exfoliated graphite oxide has a surface that has been at least partially functionalized.

  4. Comportamiento del hierro nodular austemperizado en condiciones de corrosión y desgaste // Behavior of austempered ductile iron under wear and corrosion conditions

    Directory of Open Access Journals (Sweden)

    L. Goyos Pérez

    1999-07-01

    Full Text Available Los hierros nodulares en general y los austemperizados en particular han sido usados con cada vez mayor frecuencia debido asus relevantes propiedades mecánicas en comparación con su costo.En el presente trabajo se valora el comportamiento del hierro nodular ante el trabajo en condiciones de desgaste y corrosión,luego de ser sometido a diferentes tratamientos de austemperizado.Fueron usados un hierro nodular aleado con níquel y molibdeno y otro no aleado. Ambos hierros fueron sometidos a diferentestratamientos de austemperización con mantenimientos isotérmicos a temperaturas entre 250°C y 425°C por tiempos entre 15 y180 minutos.Las muestras tratadas fueron sometidas a ensayos de desgaste por fricción en condiciones no lubricadas determinando laspendientes de desgaste uniforme para cada caso. La resistencia a la corrosión fue determinada mediante el métodopotenciométrico usando como medio el jugo de caña sintético.A partir de los resultados obtenidos se valora la influencia de los diferentes tratamientos sobre las propiedades estudiadas y sedeterminan los más efectivos desde el punto de vista técnico económico.Palabras claves: Hierro nodular, corrosión, desgaste, austemperizado.____________________________________________________________________________AbstractNodular irons and particularly austempered ductile iron has been used more and more due to their excellent mechanicalproperties in comparison with their cost.Presently work deals on behavior of nodular iron working under wear and corrosion conditions, after being submitted todifferent austempered treatments.A nodular iron alloyed with nickel and molybdenum were used as well as a not alloyed one. Both irons were treated underdifferent austempered treatment combinations using isothermal maintenance to temperatures between 250°C and 425°C andspending times between 15 and 180 minutes.Samples were submitted to non-lubricated wear using a “pin on disk” method evaluating the

  5. Effects of austempered temperature on corrosive wear behavior of carbidic austempered ductile iron%淬火温度对含碳化物等温淬火球墨铸铁耐腐蚀磨损性能的影响

    Institute of Scientific and Technical Information of China (English)

    李国禄; 董天顺; 刘金海; 张建军

    2014-01-01

    In order to study the effects of austempered temperature on corrosive wear behaviors of carbidic austempered ductile iron (CADI), the CADI was prepared, and the wear corrosion resistance test was conducted in acid medium, neutral medium and alkaline medium, respectively. The results show that in acid medium and alkaline medium, the mass loss of CADI first increased and then decreased with increasing austempered temperature. But in neutral medium, the mass loss of CADI increased gradually with increasing austempered temperature. The performance of corrosion wear resistance of CADI in acid medium is inferior to that in alkaline medium and neutral medium. While the performance of corrosion wear resistance of CADI is obviously superior to that of low chromium white cast iron under different pH values medium. Therefore, CADI is a material with good property of corrosion wear resistance.%通过等温淬火获得含碳化物等温淬火球墨铸铁(carbidic austempered ductile iron,简称CADI),并分别在中性、酸性和碱性腐蚀介质中进行腐蚀磨损实验,研究淬火温度对CADI在不同腐蚀介质中耐腐蚀磨损特性的影响,并与低铬铸铁进行对比。结果表明:在酸性和碱性介质中,CADI 的质量磨损随等温淬火温度升高先增加,然后再减少;在中性介质中,CADI 的质量磨损随等温淬火温度升高而逐渐增加;CADI 在酸性介质中的耐腐蚀磨损性能相对较差;CADI在不同pH值溶液中的耐磨损性能均优于低铬铸铁,是一种优良的耐腐蚀磨损材料。

  6. Superconductivity in graphite intercalation compounds

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert P. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Weller, Thomas E.; Howard, Christopher A. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Dean, Mark P.M. [Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Rahnejat, Kaveh C. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Saxena, Siddharth S. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Ellerby, Mark, E-mail: mark.ellerby@ucl.ac.uk [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom)

    2015-07-15

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC{sub 6} and YbC{sub 6} in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

  7. Graphite oral tattoo: case report.

    Science.gov (United States)

    Moraes, Renata Mendonça; Gouvêa Lima, Gabriela de Morais; Guilhermino, Marinaldo; Vieira, Mayana Soares; Carvalho, Yasmin Rodarte; Anbinder, Ana Lia

    2015-10-16

    Pigmented oral lesions compose a large number of pathological entities, including exogenous pigmentat oral tattoos, such as amalgam and graphite tattoos. We report a rare case of a graphite tattoo on the palate of a 62-year-old patient with a history of pencil injury, compare it with amalgam tattoos, and determine the prevalence of oral tattoos in our Oral Pathology Service. We also compare the clinical and histological findings of grafite and amalgam tattoos. Oral tattoos affect women more frequently in the region of the alveolar ridge. Graphite tattoos occur in younger patients when compared with the amalgam type. Histologically, amalgam lesions represent impregnation of the reticular fibers of vessels and nerves with silver, whereas in cases of graphite tattoos, this impregnation is not observed, but it is common to observe a granulomatous inflammatory response, less evident in cases of amalgam tattoos. Both types of lesions require no treatment, but in some cases a biopsy may be done to rule out melanocytic lesions.

  8. Graphite nanoreinforcements in polymer nanocomposites

    Science.gov (United States)

    Fukushima, Hiroyuki

    Nanocomposites composed of polymer matrices with clay reinforcements of less than 100 nm in size, are being considered for applications such as interior and exterior accessories for automobiles, structural components for portable electronic devices, and films for food packaging. While most nanocomposite research has focused on exfoliated clay platelets, the same nanoreinforcement concept can be applied to another layered material, graphite, to produce nanoplatelets and nanocomposites. Graphite is the stiffest material found in nature (Young's Modulus = 1060 GPa), having a modulus several times that of clay, but also with excellent electrical and thermal conductivity. The key to utilizing graphite as a platelet nanoreinforcement is in the ability to exfoliate this material. Also, if the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with not only excellent mechanical properties but electrical properties as well, opening up many new structural applications as well as non-structural ones where electromagnetic shielding and high thermal conductivity are requirements. In this research, a new process to fabricate exfoliated nano-scale graphite platelets was established (Patent pending). The size of the resulted graphite platelets was less than 1 um in diameter and 10 nm in thickness, and the surface area of the material was around 100 m2/g. The reduction of size showed positive effect on mechanical properties of composites because of the increased edge area and more functional groups attached with it. Also various surface treatment techniques were applied to the graphite nanoplatelets to improve the surface condition. As a result, acrylamide grafting treatment was found to enhance the dispersion and adhesion of graphite flakes in epoxy matrices. The resulted composites showed better mechanical properties than those with commercially available carbon fibers, vapor grown carbon fibers

  9. Enhanced angiogenic effect of adipose-derived stromal cell spheroid with low-level light therapy in hindlimb ischemia mice

    Science.gov (United States)

    Park, In-Su; Ahn, Jin-Chul; Chung, Phil-Sang

    2014-02-01

    Adipose-derived stromal cells (ASCs) are attractive cell source for tissue engineering. However, one obstacle to this approach is that the transplanted ASC population can decline rapidly in the recipient tissue. The aim of this study was to investigate the effects of low-level laser therapy (LLLT) on transplanted human ASCs (hASCs) spheroid in a hindlimb ischemia animal model. LLLT, hASCs spheroid and hASCs spheroid transplantation with LLLT (spheroid + LLLT) were applied to the ischemic hindlimbs in athymic mice. The survival, differentiation and secretion of vascular endothelial growth (VEGF) of spheroid ASCs were evaluated by immunohistochemistry. The spheroid + LLLT group enhanced the tissue regeneration, including angiogenesis, compared with other groups. The spheroid contributed tissue regeneration via differentiation and secretion of growth factors. In the spheroid + LLLT group, the survival of spheroid hASCs was increased by the decreased apoptosis of spheroid hASCs in the ischemic hindlimb. The secretion of growth factors was stimulated in the spheroid + LLLT group compared with the ASCs group and spheroid group. These data suggest that LLLT is an effective biostimulator of spheroid hASCs in tissue regeneration that enhances the survival of ASCs and stimulates the secretion of growth factors in the ischemic hindlimb.

  10. Intraluminal Injection of Mesenchymal Stromal Cells in Spheroids Attenuates Experimental Colitis.

    Science.gov (United States)

    Molendijk, Ilse; Barnhoorn, Marieke C; de Jonge-Muller, Eveline S M; Mieremet-Ooms, Marij A C; van der Reijden, Johan J; van der Helm, Danny; Hommes, Daniel W; van der Meulen-de Jong, Andrea E; Verspaget, Hein W

    2016-08-01

    In recent years, mesenchymal stromal cells [MSCs] emerged as a promising therapeutic option for various diseases, due to their immunomodulatory properties. We previously observed that intraperitoneally injected MSCs in experimental colitis form spherical shaped aggregates. Therefore, we aggregated MSCs in vitro into spheroids and injected them intraluminally in mice with established colitis, to investigate whether these MSC spheroids could alleviate the colitis. We injected 0.5 x 10(6) MSCs in spheroids, 2.0 x 10(6) MSCs in spheroids, or phosphate-buffered saline [PBS] as a treatment control, via an enema in mice with established dextran sulphate sodium [DSS]-induced colitis. Body weight was measured daily and disease activity score was determined at sacrifice. Endoscopy was performed to evaluate mucosal healing. After sacrifice, both systemic and local inflammatory responses were evaluated. Intraluminally injected MSC spheroids alleviated DSS-induced colitis, resulting in significantly less body weight loss and lower disease activity score at sacrifice when a high dose of MSC spheroids was administered. However, the percentage of mucosal lesions in the distal colon and endoscopy scores were not significantly lower after treatment with 2.0 x 10(6) MSCs in spheroids compared with PBS-treated mice. Systemic inflammation marker serum amyloid A [SAA] was significantly reduced after treatment with 2.0 x 10(6) MSCs in spheroids. In addition, local cytokine levels of IFN-ɣ, TNF-α, IL-6, and IL-17a, as well as numbers of macrophages and neutrophils, showed a clear decrease-though not always significant-after intraluminal injection of the MSC spheroids. Intraluminally injected MSC spheroids at least partially attenuate experimental colitis, with fewer phagocytes and proinflammmatory cytokines, when a high dose of MSCs in spheroids was administered. Copyright © 2016 European Crohn’s and Colitis Organisation (ECCO). Published by Oxford University Press. All rights

  11. Study of the influence of Cu and Ni on the kinetics of strain-induced martensite in austempered ductile cast iron; Estudio de la influencia del Cu y Ni en la cinetica de transformacion martensitica inducida por deformacion en fundiciones nodulares austemperadas

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, D.; Navea, L.; Garin, J.; Aguilar, C.; Guzman, A.

    2013-09-01

    The objective of this work was to study the influence of copper and nickel on the kinetics of strain-induced martensite in austempered ductile cast iron. The austempered ductile cast irons were obtained from two ductile cast irons with different copper and nickel contents by means of austempering treatment. The deformation was carried out using a rolling mill. The quantification of the phases was obtained by means of X ray diffraction, while the microstructural characterization was carried out using optical and scanning electron microscopy. It was proved that the kinetics of strain-induced martensite in austempered ductile cast iron can be modeled using the equations proposed by Olson- Cohen and Chang et al. Based on the results obtained from these analyses, it is possible to conclude that the nickel and copper complicate the martensite transformation because these elements increase the staking fault energy of the austenite and its thermodynamic stability. (Author)

  12. SUPERMASSIVE BLACK HOLES AND THEIR HOST SPHEROIDS. I. DISASSEMBLING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Savorgnan, G. A. D.; Graham, A. W., E-mail: gsavorgn@astro.swin.edu.au [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia)

    2016-01-15

    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using 3.6 μm Spitzer imagery, which is a superb tracer of the stellar mass (superior to the K band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction, and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and—for the first time—2D kinematics, we were able to account for spheroids; large-scale, intermediate-scale, and nuclear disks; bars; rings; spiral arms; halos; extended or unresolved nuclear sources; and partially depleted cores. For each individual galaxy, we compared our best-fit model with previous studies, explained the discrepancies, and identified the optimal decomposition. Moreover, we have independently performed one-dimensional (1D) and two-dimensional (2D) decompositions and concluded that, at least when modeling large, nearby galaxies, 1D techniques have more advantages than 2D techniques. Finally, we developed a prescription to estimate the uncertainties on the 1D best-fit parameters for the 66 spheroids that takes into account systematic errors, unlike popular 2D codes that only consider statistical errors.

  13. OVCAR-3 spheroid-derived cells display distinct metabolic profiles.

    Directory of Open Access Journals (Sweden)

    Kathleen A Vermeersch

    Full Text Available Recently, multicellular spheroids were isolated from a well-established epithelial ovarian cancer cell line, OVCAR-3, and were propagated in vitro. These spheroid-derived cells displayed numerous hallmarks of cancer stem cells, which are chemo- and radioresistant cells thought to be a significant cause of cancer recurrence and resultant mortality. Gene set enrichment analysis of expression data from the OVCAR-3 cells and the spheroid-derived putative cancer stem cells identified several metabolic pathways enriched in differentially expressed genes. Before this, there had been little previous knowledge or investigation of systems-scale metabolic differences between cancer cells and cancer stem cells, and no knowledge of such differences in ovarian cancer stem cells.To determine if there were substantial metabolic changes corresponding with these transcriptional differences, we used two-dimensional gas chromatography coupled to mass spectrometry to measure the metabolite profiles of the two cell lines.These two cell lines exhibited significant metabolic differences in both intracellular and extracellular metabolite measurements. Principal components analysis, an unsupervised dimensional reduction technique, showed complete separation between the two cell types based on their metabolite profiles. Pathway analysis of intracellular metabolomics data revealed close overlap with metabolic pathways identified from gene expression data, with four out of six pathways found enriched in gene-level analysis also enriched in metabolite-level analysis. Some of those pathways contained multiple metabolites that were individually statistically significantly different between the two cell lines, with one of the most broadly and consistently different pathways, arginine and proline metabolism, suggesting an interesting hypothesis about cancerous and stem-like metabolic phenotypes in this pair of cell lines.Overall, we demonstrate for the first time that metabolism

  14. Graphite Surface Modification by Heterogeneous Nucleation Process

    Institute of Scientific and Technical Information of China (English)

    CAO Ran; LI Hongxia

    2006-01-01

    Flaky graphite particles were coated by ZrOCl2·8H2O as precursors by heterogeneous nucleation process.The effects of factors such as pH values (2.4-5.1),concentration of the precursor solution (0.005-0.1 mol·L-1 ) , mixing method of graphite and precursor solution on the surface modification of graphite were studied. Result shows that: 1) the preferable technical process for heterogeneous nucleation modified graphite is to mix the graphite suspension and precursor solution with concentration 0. 025 mol·L -1 and then drip ammonia water to adjust the pH value to 3.6; 2)By surface modification, the ZrO2 particles are evenly coated on graphite surface and therefore improve oxidation resistance and dispersion ability of graphite.

  15. AGC-2 Graphite Preirradiation Data Package

    Energy Technology Data Exchange (ETDEWEB)

    David Swank; Joseph Lord; David Rohrbaugh; William Windes

    2012-10-01

    The NGNP Graphite R&D program is currently establishing the safe operating envelope of graphite core components for a Very High Temperature Reactor (VHTR) design. The program is generating quantitative data necessary for predicting the behavior and operating performance of the new nuclear graphite grades. To determine the in-service behavior of the graphite for pebble bed and prismatic designs, the Advanced Graphite Creep (AGC) experiment is underway. This experiment is examining the properties and behavior of nuclear grade graphite over a large spectrum of temperatures, neutron fluences and compressive loads. Each experiment consists of over 400 graphite specimens that are characterized prior to irradiation and following irradiation. Six experiments are planned with the first, AGC-1, currently being irradiated in the Advanced Test Reactor (ATR) and pre-irradiation characterization of the second, AGC-2, completed. This data package establishes the readiness of 512 specimens for assembly into the AGC-2 capsule.

  16. Microstructure transformation of carbon nanofibers during graphitization

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong; TANG Yuan-hong; LIN Liang-wu; ZHANG En-lei

    2008-01-01

    The mierostructures of vapor-grown carbon nanofibers(CNFs) before and after graphitization process were analyzed by high resolution transmission electron microscopy(HRTEM), Raman spectroscopy, X-ray diffractometry(XRD), near-edge-X-ray absorption fine structure spectroscopy(NEXAFS) and thermogravimetric analysis(TGA). The results indicate that although non-graphitized CNFs have the characteristics of higher disorder, a transformation is found in the inner layer of tube wall where graphite sheets become stiff, which demonstrates the characteristics of higher graphitization of graphitized CNFs. The defects in outer tube wall disappear because the amorphous carbon changes to perfect crystalline carbon after annealing treatment at about 2 800 ℃. TGA analysis in air indicates that graphitized CNFs have excellent oxidation resistance up to 857 ℃. And the graphitization mechanism including four stages was also proposed.

  17. Note: 3D printed spheroid for uniform magnetic field generation

    Science.gov (United States)

    Öztürk, Y.; Aktaş, B.

    2016-10-01

    This article is focused on a novel and practical production method for a uniform magnetic field generator. The method involves building of a surface coil template using a desktop 3D printer and winding of a conducting wire onto the structure using surface grooves as a guide. Groove pattern was based on the parametric spheroidal helical coil formula. The coil was driven by a current source and the magnetic field inside was measured using a Hall probe placed into the holes on the printed structure. The measurements are found to be in good agreement with our finite element analysis results and indicate a fairly uniform field inside.

  18. Chemical Evolution of Mn in Three Dwarf Spheroidal Galaxies

    Indian Academy of Sciences (India)

    Men-Quan Liu; Jie Zhang

    2014-09-01

    Based on an improved model, more reasonable nucleosyn-thesis and explosion rate of SNeIa and CCSNe, we studied Mn evolution for three local dwarf spheroidal galaxies (dSphs), considering the detailed SNe yield and explosion rates for different types of progenitors. The results can explain the main observation ofMn abundance for tens stars in those dSphs, and give some constraints to the nucleosynthesis and explosion ratio of different types of supernovae and Star Formation Rates (SFR) in those dSphs.

  19. Short-term effects of radiation in glioblastoma spheroids

    DEFF Research Database (Denmark)

    Asferg Petterson, Stine; Pind Jakobsen, Ida; Jensen, Stine Skov;

    2016-01-01

    and five days. We found a small reduction in primary spheroid size after radiation and an associated small increase in uptake of the cell death marker propidium iodide. Using immunohistochemistry, P53 expression was found to be significantly increased, whereas the Ki-67 proliferation index...... capacity. Gene expression analysis of nine stem cell- and two hypoxia-related genes did not reveal any upregulation after radiation. In conclusion, this study suggests that a major short-term effect of radiation is pronounced reduction of tumor cell proliferation. We found no upregulation of stem cell...

  20. VARIATIONS IN A UNIVERSAL DARK MATTER PROFILE FOR DWARF SPHEROIDALS

    Energy Technology Data Exchange (ETDEWEB)

    Jardel, John R.; Gebhardt, Karl, E-mail: jardel@astro.as.utexas.edu [Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712 (United States)

    2013-09-20

    Using a newly developed modeling technique, we present orbit-based dynamical models of the Carina, Draco, Fornax, Sculptor, and Sextans dwarf spheroidal (dSph) galaxies. These models calculate the dark matter profiles non-parametrically without requiring any assumptions to be made about their profile shapes. By lifting this restriction, we discover a host of dark matter profiles in the dSphs that are different from the typical profiles suggested by both theorists and observers. However, when we scale these profiles appropriately and plot them on a common axis, they appear to follow an approximate r {sup –1} power law with considerable scatter.

  1. Trigonometric potentials arising from the spheroidal equation: Supersymmetric partners and integral formulas

    Science.gov (United States)

    Schulze-Halberg, Axel

    2016-06-01

    We construct supersymmetric partners of a quantum system featuring a class of trigonometric potentials that emerge from the spheroidal equation. Examples of both standard and confluent supersymmetric transformations are presented. Furthermore, we use integral formulas arising from the confluent supersymmetric formalism to derive new representations for single and multiple integrals of spheroidal functions.

  2. Galaxy And Mass Assembly (GAMA): the Stellar Mass Budget of Galaxy Spheroids and Disks

    CERN Document Server

    Moffett, Amanda J; Driver, Simon P; Robotham, Aaron S G; Kelvin, Lee S; Alpaslan, Mehmet; Andrews, Stephen K; Bland-Hawthorn, Joss; Brough, Sarah; Cluver, Michelle E; Colless, Matthew; Davies, Luke J M; Holwerda, Benne W; Hopkins, Andrew M; Kafle, Prajwal R; Liske, Jochen; Meyer, Martin

    2016-01-01

    We build on a recent photometric decomposition analysis of 7506 Galaxy and Mass Assembly (GAMA) survey galaxies to derive stellar mass function fits to individual spheroid and disk component populations down to a lower mass limit of log(M_*/M_sun)= 8. We find that the spheroid/disk mass distributions for individual galaxy morphological types are well described by single Schechter function forms. We derive estimates of the total stellar mass densities in spheroids (rho_spheroid = 1.24+/-0.49 * 10^8 M_sun Mpc^-3 h_0.7) and disks (rho_disk = 1.20+/-0.45 * 10^8 M_sun Mpc^-3 h_0.7), which translates to approximately 50% of the local stellar mass density in spheroids and 48% in disks. The remaining stellar mass is found in the dwarf "little blue spheroid" class, which is not obviously similar in structure to either classical spheroid or disk populations. We also examine the variation of component mass ratios across galaxy mass and group halo mass regimes, finding the transition from spheroid to disk mass dominance ...

  3. Generation of Multicellular Breast Cancer Tumor Spheroids: Comparison of Different Protocols.

    Science.gov (United States)

    Froehlich, Karolin; Haeger, Jan-Dirk; Heger, Julia; Pastuschek, Jana; Photini, Stella Mary; Yan, Yan; Lupp, Amelie; Pfarrer, Christiane; Mrowka, Ralf; Schleußner, Ekkehard; Markert, Udo R; Schmidt, André

    2016-12-01

    Multicellular tumor spheroids are widely used models in tumor research. Because of their three dimensional organization they can simulate avascular tumor areas comprising proliferative and necrotic cells. Nonetheless, protocols for spheroid generation are still inconsistent. Therefore, in this study the breast cancer cell lines MCF-7, MDA-MB-231 and SK-BR-3 have been used to compare different spheroid generation models including hanging drop, liquid overlay and suspension culture techniques, each under several conditions. Experimental approaches differed in cell numbers (400-10,000), media and additives (25 % methocel, 25 % methocel plus 1 % Matrigel, 3.5 % Matrigel). In total, 42 different experimental setups have been tested. Generation of spheroids was evaluated by light microscopy and the structural composition was assessed immunohistochemically by means of Ki-67, cleaved poly (ADP-ribose) polymerase (cPARP) and mucin-1 (MUC-1) expression. Although the tested cell lines diverged widely in their capacity of forming spheroids we recommend hanging drops supplemented with 25 % methocel as the most reliable and efficient method with regard to success of generation of uniform spheroids, costs, experimental complexity and time expenditure in the different cell lines. MCF-7 cells formed spheroids under almost all analyzed conditions, and MDA-MB-231 cells under only one protocol (liquid overlay technique, 3.5 % Matrigel), while SK-BR-3 did not under neither condition. Therefore, we outline specific methods and recommend the use of adapted and standardized spheroid generation protocols for each cell line.

  4. Surface electric current distributions on spheres and spheroids as sources of pure quadrupole magnetic fields

    OpenAIRE

    L. Medina; E. Ley-Koo

    2011-01-01

    Neutral atom magnetic traps and nuclear magnetic resonance imaging require internal regions with constant gradient magnetic induction fields, which are identified as pure quadrupole fields. This contribution starts from such fields in the interior of spheres and spheroids in cartesian coordinates, identifying immediately their respective scalar magnetic potentials. Next, the corresponding potentials inside and outside are constructed using spherical and spheroidal harmonic functions, respecti...

  5. Rapid generation of single-tumor spheroids for high-throughput cell function and toxicity analysis.

    Science.gov (United States)

    Ivascu, Andrea; Kubbies, Manfred

    2006-12-01

    Spheroids are widely used in biology because they provide an in vitro 3-dimensional (3D) model to study proliferation, cell death, differentiation, and metabolism of cells in tumors and the response of tumors to radiotherapy and chemotherapy. The methods of generating spheroids are limited by size heterogeneity, long cultivation time, or mechanical accessibility for higher throughput fashion. The authors present a rapid method to generate single spheroids in suspension culture in individual wells. A defined number of cells ranging from 1000 to 20,000 were seeded into wells of poly-HEMA-coated, 96-well, round-or conical-bottom plates in standard medium and centrifuged for 10 min at 1000 g. This procedure generates single spheroids in each well within a 24-h culture time with homogeneous sizes, morphologies, and stratification of proliferating cells in the rim and dying cells in the core region. Because a large number of tumor cell lines form only loose aggregates when cultured in 3D, the authors also performed a screen for medium additives to achieve a switch from aggregate to spheroid morphology. Small quantities of the basement membrane extract Matrigel, added to the culture medium prior to centrifugation, most effectively induced compact spheroid formation. The compact spheroid morphology is evident as early as 24 h after centrifugation in a true suspension culture. Twenty tumor cell lines of different lineages have been used to successfully generate compact, single spheroids with homogenous size in 96-well plates and are easily accessible for subsequent functional analysis.

  6. Abnormal hepatic copper accumulation of spheroid composed of liver cells from LEC rats in vitro.

    Science.gov (United States)

    Ueno, K; Yoshizawa, M; Satoh, T; Yoneda, S; Ohmichi, M; Yamazaki, M; Mori, Y; Suzuki, K T

    1995-11-01

    The LEC rat is a mutant strain displaying hereditary hepatitis, and shows abnormal accumulation of copper (Cu) similar to that occurring in Wilson's disease. We prepared a multicellular spheroid composed of LEC rat liver cells to investigate the mechanism for abnormal accumulation of Cu. These multicellular spheroids were prepared by detaching the monolayer on the collagen-conjugated thermo-responsive polymer coated culture dish at a temperature below the critical solution temperature and culturing on the non-adhesive substratum. Long-term cultured spheroids of LEC rat liver cells as well as SD rat liver cells were attempted. Non-parenchymal cells obtained by collagenase perfusion from the LEC liver were fewer than those from the SD liver. Cells from the LEC rat, over 11 weeks of age, did not form a cell sheet; however, a mixture of parenchymal cells from LEC rats over aged 11 weeks and non-parenchymal cells from SD rats of any age yielded intact spheroids. We examined the toxicity, the accumulation and distribution of Cu in spheroids. The accumulation of Cu in LEC spheroids was higher than that in SD spheroids. Results suggest that spheroids consisting of LEC liver cells are useful as an alternative model to in vivo tests to investigate the mechanism for abnormal accumulation of Cu in liver.

  7. Spot feeding spheroidal graphite iron with exothermic and insulating ram-up sleeves in vertically parted moulds

    DEFF Research Database (Denmark)

    Vedel-Smith, Nikolaj Kjelgaard

    2016-01-01

    Improvement of feeder technologies for energy savings incast iron foundries is not only the title of the project behind this dissertation, it is a good idea that can improve casting yield and reduce production cost, and in turn strengthening the foundries competitive advantage. The approach...... to solving feeding problems today is for a large part based on methodologies and know-how developed more than 50 years ago. This dissertation addresses the state-of-the-art as it is used presently in the foundries, reviewing the fundamentals of spot feeding cast iron....

  8. Multiplexing spheroid volume, resazurin and acid phosphatase viability assays for high-throughput screening of tumour spheroids and stem cell neurospheres.

    Science.gov (United States)

    Ivanov, Delyan P; Parker, Terry L; Walker, David A; Alexander, Cameron; Ashford, Marianne B; Gellert, Paul R; Garnett, Martin C

    2014-01-01

    Three-dimensional cell culture has many advantages over monolayer cultures, and spheroids have been hailed as the best current representation of small avascular tumours in vitro. However their adoption in regular screening programs has been hindered by uneven culture growth, poor reproducibility and lack of high-throughput analysis methods for 3D. The objective of this study was to develop a method for a quick and reliable anticancer drug screen in 3D for tumour and human foetal brain tissue in order to investigate drug effectiveness and selective cytotoxic effects. Commercially available ultra-low attachment 96-well round-bottom plates were employed to culture spheroids in a rapid, reproducible manner amenable to automation. A set of three mechanistically different methods for spheroid health assessment (Spheroid volume, metabolic activity and acid phosphatase enzyme activity) were validated against cell numbers in healthy and drug-treated spheroids. An automated open-source ImageJ macro was developed to enable high-throughput volume measurements. Although spheroid volume determination was superior to the other assays, multiplexing it with resazurin reduction and phosphatase activity produced a richer picture of spheroid condition. The ability to distinguish between effects on malignant and the proliferating component of normal brain was tested using etoposide on UW228-3 medulloblastoma cell line and human neural stem cells. At levels below 10 µM etoposide exhibited higher toxicity towards proliferating stem cells, whereas at concentrations above 10 µM the tumour spheroids were affected to a greater extent. The high-throughput assay procedures use ready-made plates, open-source software and are compatible with standard plate readers, therefore offering high predictive power with substantial savings in time and money.

  9. Multiplexing spheroid volume, resazurin and acid phosphatase viability assays for high-throughput screening of tumour spheroids and stem cell neurospheres.

    Directory of Open Access Journals (Sweden)

    Delyan P Ivanov

    Full Text Available Three-dimensional cell culture has many advantages over monolayer cultures, and spheroids have been hailed as the best current representation of small avascular tumours in vitro. However their adoption in regular screening programs has been hindered by uneven culture growth, poor reproducibility and lack of high-throughput analysis methods for 3D. The objective of this study was to develop a method for a quick and reliable anticancer drug screen in 3D for tumour and human foetal brain tissue in order to investigate drug effectiveness and selective cytotoxic effects. Commercially available ultra-low attachment 96-well round-bottom plates were employed to culture spheroids in a rapid, reproducible manner amenable to automation. A set of three mechanistically different methods for spheroid health assessment (Spheroid volume, metabolic activity and acid phosphatase enzyme activity were validated against cell numbers in healthy and drug-treated spheroids. An automated open-source ImageJ macro was developed to enable high-throughput volume measurements. Although spheroid volume determination was superior to the other assays, multiplexing it with resazurin reduction and phosphatase activity produced a richer picture of spheroid condition. The ability to distinguish between effects on malignant and the proliferating component of normal brain was tested using etoposide on UW228-3 medulloblastoma cell line and human neural stem cells. At levels below 10 µM etoposide exhibited higher toxicity towards proliferating stem cells, whereas at concentrations above 10 µM the tumour spheroids were affected to a greater extent. The high-throughput assay procedures use ready-made plates, open-source software and are compatible with standard plate readers, therefore offering high predictive power with substantial savings in time and money.

  10. A theoretical study of the spheroidal droplet evaporation in forced convection

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jie, E-mail: leejay1986@163.com; Zhang, Jian

    2014-11-07

    In many applications, the shape of a droplet may be assumed to be an oblate spheroid. A theoretical study is conducted on the evaporation of an oblate spheroidal droplet under forced convection conditions. Closed-form analytical expressions of the mass evaporation rate for an oblate spheroid are derived, in the regime of controlled mass-transfer and heat-transfer, respectively. The variation of droplet size during the evaporation process is presented in the regime of shrinking dynamic model. Comparing with the droplets having the same surface area, an increase in the aspect ratio enhances the mass evaporation rate and prolongs the burnout time. - Highlights: • Fully algebraic solutions for the spheroidal droplet evaporation rate is obtained. • We examine the effect of aspect ratio on the droplet evaporation. • We propose a calculation method of Nusselt number for spheroidal droplet.

  11. The low-frequency dielectric response of charged oblate spheroidal particles immersed in an electrolyte

    CERN Document Server

    Hou, Chang-Yu; Sen, Pabitra N

    2016-01-01

    We study the low-frequency polarization response of a surface-charged oblate spheroidal particle immersed in an electrolyte solution. Because the charged spheroid attracts counter-ions which form the electric double layer around the particle, using usual boundary conditions at the interface between the particle and electrolyte can be quite complicated and challenging. Hence, we generalize Fixman's boundary conditions, originally derived for spherical particles, to the case of the charged oblate spheroid. Given two different counter-ion distributions in the thin electric double layer limit, we obtain analytic expressions for the polarization coefficients to the first non-trivial order in frequency. We find that the polarization response normal to the symmetry axis depends on the total amount of charge carried by the oblate spheroid while that parallel to the symmetry axis is suppressed when there is less charge on the edge of the spheroid. We further study the overall dielectric response for a dilute suspensio...

  12. High-Throughput Spheroid Screens Using Volume, Resazurin Reduction, and Acid Phosphatase Activity.

    Science.gov (United States)

    Ivanov, Delyan P; Grabowska, Anna M; Garnett, Martin C

    2017-01-01

    Mainstream adoption of physiologically relevant three-dimensional models has been slow in the last 50 years due to long, manual protocols with poor reproducibility, high price, and closed commercial platforms. This chapter describes high-throughput, low-cost, open methods for spheroid viability assessment which use readily available reagents and open-source software to analyze spheroid volume, metabolism, and enzymatic activity. We provide two ImageJ macros for automated spheroid size determination-for both single images and images in stacks. We also share an Excel template spreadsheet allowing users to rapidly process spheroid size data, analyze plate uniformity (such as edge effects and systematic seeding errors), detect outliers, and calculate dose-response. The methods would be useful to researchers in preclinical and translational research planning to move away from simplistic monolayer studies and explore 3D spheroid screens for drug safety and efficacy without substantial investment in money or time.

  13. Building Blocks of the Milky Way's Accreted Spheroid

    CERN Document Server

    van Oirschot, Pim; Helmi, Amina; Nelemans, Gijs

    2016-01-01

    In the $\\Lambda$CDM model of structure formation, a stellar spheroid grows by the assembly of smaller galaxies, the so-called building blocks. Combining the Munich-Groningen semi-analytical model of galaxy formation with the high resolution Aquarius simulations of dark matter haloes, we study the assembly history of the stellar spheroids of six Milky Way-mass galaxies, focussing on building block properties such as mass, age and metallicity. These properties are compared to those of the surviving satellites in the same models. We find that the building blocks have higher star formation rates on average, and this is especially the case for the more massive objects. At high redshift these dominate in star formation over the satellites, whose star formation timescales are longer on average. These differences ought to result in a larger $\\alpha$-element enhancement from Type II supernovae in the building blocks (compared to the satellites) by the time Type Ia supernovae would start to enrich them in iron, explain...

  14. Mergers and the outside-in formation of dwarf spheroidals

    CERN Document Server

    Benítez-Llambay, Alejandro; Abadi, Mario G; Gottloeber, Stefan; Yepes, Gustavo; Hoffman, Yehuda; Steinmetz, Matthias

    2015-01-01

    We use a cosmological simulation of the formation of the Local Group to explore the origin of age and metallicity gradients in dwarf spheroidal galaxies. We find that a number of simulated dwarfs form "outside-in", with an old, metal-poor population that surrounds a younger, more concentrated metal-rich component, reminiscent of dwarf spheroidals like Sculptor or Sextans. We focus on a few examples where stars form in two populations distinct in age in order to elucidate the origin of these gradients. The spatial distributions of the two components reflect their diverse origin; the old stellar component is assembled through mergers, but the young population forms largely in situ. The older component results from a first episode of star formation that begins early but is quickly shut off by the combined effects of stellar feedback and reionization. The younger component forms when a late accretion event adds gas and reignites star formation. The effect of mergers is to disperse the old stellar population, incr...

  15. Structural analysis of the Sextans dwarf spheroidal galaxy

    Science.gov (United States)

    Roderick, T. A.; Jerjen, H.; Da Costa, G. S.; Mackey, A. D.

    2016-07-01

    We present wide-field g- and i-band stellar photometry of the Sextans dwarf spheroidal galaxy and its surrounding area out to four times its half-light radius (rh = 695 pc), based on images obtained with the Dark Energy Camera at the 4-m Blanco telescope at CTIO. We find clear evidence of stellar substructure associated with the galaxy, extending to a distance of 82 arcmin (2 kpc) from its centre. We perform a statistical analysis of the overdensities and find three distinct features, as well as an extended halo-like structure, to be significant at the 99.7 per cent confidence level or higher. Unlike the extremely elongated and extended substructures surrounding the Hercules dwarf spheroidal galaxy, the overdensities seen around Sextans are distributed evenly about its centre, and do not appear to form noticeable tidal tails. Fitting a King model to the radial distribution of Sextans stars yields a tidal radius rt = 83.2 arcmin ± 7.1 arcmin (2.08 ± 0.18 kpc), which implies the majority of detected substructure is gravitationally bound to the galaxy. This finding suggests that Sextans is not undergoing significant tidal disruption from the Milky Way, supporting the scenario in which the orbit of Sextans has a low eccentricity.

  16. Dynamics of prolate spheroidal mass distributions with varying eccentricity

    CERN Document Server

    Rathulnath, R

    2013-01-01

    In this paper we calculate the potential for a prolate spheroidal distribution as in a dark matter halo with a radially varying eccentricity. This is obtained by summing up the shell-by-shell contributions of isodensity surfaces, which are taken to be concentric and with a common polar axis and with an axis ratio that varies with radius. Interestingly, the constancy of potential inside a shell is shown to be a good approximation even when the isodensity contours are dissimilar spheroids, as long as the radial variation in eccentricity is small as seen in realistic systems. We consider three cases where the isodensity contours are more prolate at large radii, or are less prolate, or have a constant eccentricity. Other relevant physical quantities like the rotation velocity, the net orbital and vertical frequency due to the halo and an exponential disc of finite thickness embedded in it are obtained. We apply this to the kinematical origin of Galactic warp, and show that a prolate shaped halo is not conducive t...

  17. Discriminating Between the Physical Processes that Drive Spheroid Size Evolution

    CERN Document Server

    Hopkins, Philip F; Hernquist, Lars; Wuyts, Stijn; Cox, Thomas J

    2009-01-01

    Massive galaxies at high-z have smaller effective radii than those today, but similar central densities. Their size growth therefore relates primarily to the evolving abundance of low-density material. Various models have been proposed to explain this evolution, which have different implications for galaxy, star, and BH formation. We compile observations of spheroid properties as a function of redshift and use them to test proposed models. Evolution in progenitor gas-richness with redshift gives rise to initial formation of smaller spheroids at high-z. These systems can then evolve in apparent or physical size via several channels: (1) equal-density 'dry' mergers, (2) later major or minor 'dry' mergers with less-dense galaxies, (3) adiabatic expansion, (4) evolution in stellar populations & mass-to-light-ratio gradients, (5) age-dependent bias in stellar mass estimators, (6) observational fitting/selection effects. If any one of these is tuned to explain observed size evolution, they make distinct predict...

  18. Study on the effects of nylon-chitosan-blended membranes on the spheroid-forming activity of human melanocytes.

    Science.gov (United States)

    Lin, Sung-Jan; Hsiao, Wen-Chu; Jee, Shiou-Hwa; Yu, Hsin-Su; Tsai, Tsen-Fang; Lai, Juin-Yih; Young, Tai-Horng

    2006-10-01

    Though reported limitedly in tissue engineering, modification of cellular functions can be achieved by culturing them into multicellular spheroids. We have shown melanocytes form spheroids on chitosan surface. However, how biomaterials promote spheroid formation has never been systemically investigated. In this work, nylon, which inhibits melanocyte spheroid formation, and chitosan, which promotes melanocyte spheroid formation, are used to prepare nylon/chitosan-blended membranes. Membranes composed of pure nylon, pure chitosan and various ratios of nylon and chitosan are employed to examine their effects on spheroid formation. Melanocytes show better adhesion to nylon membranes than that to chitosan membranes. In blended membranes, as more nylon is incorporated, cell adhesion increases and the trend for spheroid formation decreases. Melanocytes can only form spheroids on membranes with poorer cell adhesion. Examining the surface of the blended membranes shows phase separation of nylon and chitosan. As nylon content increases, the nylon phase on the membrane surface increases and thereby enhances cell adhesion. The opposite trend for cell adhesion and spheroid formation substantiates our hypothesis of spheroid formation on biomaterials: a balance between cell-substrate interaction and cell-cell interaction. The decrease in cell-substrate interaction tilts the balance to a state more favorable for spheroid formation. Our work can serve as a model to investigate the relative strengths of cell-cell and cell-substrate interactions and also pave way to design blended membranes with desired physical properties while preserving the spheroid-forming activity.

  19. AGC-3 Graphite Preirradiation Data Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    William Windes; David Swank; David Rohrbaugh; Joseph Lord

    2013-09-01

    This report describes the specimen loading order and documents all pre-irradiation examination material property measurement data for the graphite specimens contained within the third Advanced Graphite Capsule (AGC-3) irradiation capsule. The AGC-3 capsule is third in six planned irradiation capsules comprising the Advanced Graphite Creep (AGC) test series. The AGC test series is used to irradiate graphite specimens allowing quantitative data necessary for predicting the irradiation behavior and operating performance of new nuclear graphite grades to be generated which will ascertain the in-service behavior of the graphite for pebble bed and prismatic Very High Temperature Reactor (VHTR) designs. The general design of AGC-3 test capsule is similar to the AGC-2 test capsule, material property tests were conducted on graphite specimens prior to loading into the AGC-3 irradiation assembly. However the 6 major nuclear graphite grades in AGC-2 were modified; two previous graphite grades (IG-430 and H-451) were eliminated and one was added (Mersen’s 2114 was added). Specimen testing from three graphite grades (PCEA, 2114, and NBG-17) was conducted at Idaho National Laboratory (INL) and specimen testing for two grades (IG-110 and NBG-18) were conducted at Oak Ridge National Laboratory (ORNL) from May 2011 to July 2013. This report also details the specimen loading methodology for the graphite specimens inside the AGC-3 irradiation capsule. The AGC-3 capsule design requires "matched pair" creep specimens that have similar dose levels above and below the neutron flux profile mid-plane to provide similar specimens with and without an applied load. This document utilized the neutron flux profile calculated for the AGC-3 capsule design, the capsule dimensions, and the size (length) of the selected graphite and silicon carbide samples to create a stacking order that can produce "matched pairs" of graphite samples above and below the AGC-3 capsule elevation mid-point to

  20. Fission Product Sorptivity in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Tompson, Jr., Robert V. [Univ. of Missouri, Columbia, MO (United States); Loyalka, Sudarshan [Univ. of Missouri, Columbia, MO (United States); Ghosh, Tushar [Univ. of Missouri, Columbia, MO (United States); Viswanath, Dabir [Univ. of Missouri, Columbia, MO (United States); Walton, Kyle [Univ. of Missouri, Columbia, MO (United States); Haffner, Robert [Univ. of Missouri, Columbia, MO (United States)

    2015-04-01

    Both adsorption and absorption (sorption) of fission product (FP) gases on/into graphite are issues of interest in very high temperature reactors (VHTRs). In the original proposal, we proposed to use packed beds of graphite particles to measure sorption at a variety of temperatures and to use an electrodynamic balance (EDB) to measure sorption onto single graphite particles (a few μm in diameter) at room temperature. The use of packed beds at elevated temperature is not an issue. However, the TPOC requested revision of this initial proposal to included single particle measurements at elevated temperatures up to 1100 °C. To accommodate the desire of NEUP to extend the single particle EDB measurements to elevated temperatures it was necessary to significantly revise the plan and the budget. These revisions were approved. In the EDB method, we levitate a single graphite particle (the size, surface characteristics, morphology, purity, and composition of the particle can be varied) or agglomerate in the balance and measure the sorption of species by observing the changes in mass. This process involves the use of an electron stepping technique to measure the total charge on a particle which, in conjunction with the measured suspension voltages for the particle, allows for determinations of mass and, hence, of mass changes which then correspond to measurements of sorption. Accommodating elevated temperatures with this type of system required a significant system redesign and required additional time that ultimately was not available. These constraints also meant that the grant had to focus on fewer species as a result. Overall, the extension of the original proposed single particle work to elevated temperatures added greatly to the complexity of the proposed project and added greatly to the time that would eventually be required as well. This means that the bulk of the experimental progress was made using the packed bed sorption systems. Only being able to recruit one

  1. Primary structural dynamics in graphite

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Sascha; Liang Wenxi; Zewail, Ahmed H, E-mail: zewail@caltech.edu [Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125 (United States)

    2011-06-15

    The structural dynamics of graphite and graphene are unique, because of the selective coupling between electron and lattice motions and hence the limit on electric and electro-optic properties. Here, we report on the femtosecond probing of graphite films (1-3 nm) using ultrafast electron crystallography in the transmission mode. Two time scales are observed for the dynamics: a 700 fs initial decrease in diffraction intensity due to lattice phonons in optically dark regions of the Brillouin zone, followed by a 12 ps decrease due to phonon thermalization near the {Gamma} and K regions. These results indicate the non-equilibrium distortion of the unit cells at early time and the subsequent role of long-wavelength atomic motions in the thermalization process. Theory and experiment are now in agreement regarding the nature of nuclear motions, but the results suggest that potential change plays a role in the lateral dynamics of the lattice.

  2. Generation of co-culture spheroids as vascularisation units for bone tissue engineering

    Directory of Open Access Journals (Sweden)

    R Walser

    2013-11-01

    Full Text Available Cell spheroids represent attractive building units for bone tissue engineering, because they provide a three-dimensional environment with intensive direct cell-cell contacts. Moreover, they allow for co-culture of both osteoblasts and vessel-forming cells, which may markedly increase their survival and vascularisation after transplantation. To test this hypothesis, we generated co-culture spheroids by aggregating different combinations of primary human osteoblasts (HOB, human dermal microvascular endothelial cells (HDMEC and normal human dermal fibroblasts (NHDF using the liquid overlay technique. Mono-culture spheroids consisting either of HOB or HDMEC served as controls. After in vitro characterisation, the different spheroids were transplanted into dorsal skinfold chambers of CD1 nu/nu mice to study in vivo their viability and vascularisation over a 2-week observation period by means of repetitive intravital fluorescence microscopy and immunohistochemistry. In vitro, co-culture spheroids containing HDMEC rapidly formed dense tubular vessel-like networks within 72 h and exhibited a significantly decreased rate of apoptotic cell death when compared to mono-culture HDMEC spheroids. After transplantation, these networks interconnected to the host microvasculature by external inosculation. Of interest, this process was most pronounced in HOB-HDMEC spheroids and could not further be improved by the addition of NHDF. Accordingly, HOB-HDMEC spheroids were larger when compared to the other spheroid types. These findings indicate that HOB-HDMEC spheroids exhibit excellent properties to preserve viability and to promote proliferation and vascularisation. Therefore, they may be used as functional vascularisation units in bone tissue engineering for the seeding of scaffolds or for the vitalisation of non-healing large bone defects.

  3. Geometric phases in graphitic cones

    Energy Technology Data Exchange (ETDEWEB)

    Furtado, Claudio [Departamento de Fisica, CCEN, Universidade Federal da Paraiba, Cidade Universitaria, 58051-970 Joao Pessoa, PB (Brazil)], E-mail: furtado@fisica.ufpb.br; Moraes, Fernando [Departamento de Fisica, CCEN, Universidade Federal da Paraiba, Cidade Universitaria, 58051-970 Joao Pessoa, PB (Brazil); Carvalho, A.M. de M [Departamento de Fisica, Universidade Estadual de Feira de Santana, BR116-Norte, Km 3, 44031-460 Feira de Santana, BA (Brazil)

    2008-08-04

    In this Letter we use a geometric approach to study geometric phases in graphitic cones. The spinor that describes the low energy states near the Fermi energy acquires a phase when transported around the apex of the cone, as found by a holonomy transformation. This topological result can be viewed as an analogue of the Aharonov-Bohm effect. The topological analysis is extended to a system with n cones, whose resulting configuration is described by an effective defect00.

  4. Chunky graphite formation in small section ductile iron castings; Formacion de grafito chunky en piezas de pequeno espesor fabricadas utilizando fundicion de hierro con grafito esferoidal

    Energy Technology Data Exchange (ETDEWEB)

    Asenjo, I.; Larranaga, P.; Sertucha, J.

    2011-07-01

    Chunky graphite is a degenerated graphite form which can be found in the thermal centre of ductile iron heavy section castings. Previous studies made on cubic blocks (300 and 180 mm in side) manufactured using alloys with fully ferritic matrix structures show that low cooling rates, excessive post-inoculation and high silicon and/or cerium contents in the melts are the most important factors that promote this kind of defect. The enhancement of these critical factors led to obtain chunky graphite in sections lower than 50 mm. Different experimental conditions have been used in order to establish the main parameters that affect this graphite malformation. The use of cutting-edge techniques in the analysis of chemical compositions has revealed that no significant differences can be found when comparing chunky areas and well-formed spheroidal graphite areas. On the other hand, it has not been possible to establish any correlation between the oxygen contents and the scale of the defect. However, it is noteworthy that the oxygen content is related to the use of magnesium or cerium as nodulized agent. (Author) 23 refs.

  5. Environmentally benign graphite intercalation compound composition for exfoliated graphite, flexible graphite, and nano-scaled graphene platelets

    Science.gov (United States)

    Zhamu, Aruna; Jang, Bor Z.

    2014-06-17

    A carboxylic-intercalated graphite compound composition for the production of exfoliated graphite, flexible graphite, or nano-scaled graphene platelets. The composition comprises a layered graphite with interlayer spaces or interstices and a carboxylic acid residing in at least one of the interstices, wherein the composition is prepared by a chemical oxidation reaction which uses a combination of a carboxylic acid and hydrogen peroxide as an intercalate source. Alternatively, the composition may be prepared by an electrochemical reaction, which uses a carboxylic acid as both an electrolyte and an intercalate source. Exfoliation of the invented composition does not release undesirable chemical contaminants into air or drainage.

  6. Uranium Oxide Aerosol Transport in Porous Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Blanchard, Jeremy; Gerlach, David C.; Scheele, Randall D.; Stewart, Mark L.; Reid, Bruce D.; Gauglitz, Phillip A.; Bagaasen, Larry M.; Brown, Charles C.; Iovin, Cristian; Delegard, Calvin H.; Zelenyuk, Alla; Buck, Edgar C.; Riley, Brian J.; Burns, Carolyn A.

    2012-01-23

    The objective of this paper is to investigate the transport of uranium oxide particles that may be present in carbon dioxide (CO2) gas coolant, into the graphite blocks of gas-cooled, graphite moderated reactors. The transport of uranium oxide in the coolant system, and subsequent deposition of this material in the graphite, of such reactors is of interest because it has the potential to influence the application of the Graphite Isotope Ratio Method (GIRM). The GIRM is a technology that has been developed to validate the declared operation of graphite moderated reactors. GIRM exploits isotopic ratio changes that occur in the impurity elements present in the graphite to infer cumulative exposure and hence the reactor’s lifetime cumulative plutonium production. Reference Gesh, et. al., for a more complete discussion on the GIRM technology.

  7. Tribology of Graphite-Filled Polystyrene

    Directory of Open Access Journals (Sweden)

    Raffaele Gilardi

    2016-06-01

    Full Text Available Self-lubricating polymer compounds are currently used for a wide range of applications such as bearings, gears, and water meters. Under severe conditions such as high pressure, high velocity, and/or high temperatures, the material fails (PV limit. In this study, we investigated the effect of graphite on the tribological properties of polystyrene (PS with “ball-on-three-plates” tests. Graphite-filled PS plates were produced via an internal mixer and compression molding. Unhardened steel (1.4401 and nylon (PA66 balls were used for the tribological tests. Our results indicate that graphite loading, graphite type, and particle size have a big influence on the friction coefficient, the wear resistance, and the PV limit of PS both against steel and PA66. In particular, primary synthetic graphite performs better than secondary synthetic graphite due to the higher degree of crystallinity.

  8. Electrochemical Ultracapacitors Using Graphitic Nanostacks

    Science.gov (United States)

    Marotta, Christopher

    2012-01-01

    Electrochemical ultracapacitors (ECs) have been developed using graphitic nanostacks as the electrode material. The advantages of this technology will be the reduction of device size due to superior power densities and relative powers compared to traditional activated carbon electrodes. External testing showed that these materials display reduced discharge response times compared to state-of-the-art materials. Such applications are advantageous for pulsed power applications such as burst communications (satellites, cell phones), electromechanical actuators, and battery load leveling in electric vehicles. These carbon nanostructures are highly conductive and offer an ordered mesopore network. These attributes will provide more complete electrolyte wetting, and faster release of stored charge compared to activated carbon. Electrochemical capacitor (EC) electrode materials were developed using commercially available nanomaterials and modifying them to exploit their energy storage properties. These materials would be an improvement over current ECs that employ activated carbon as the electrode material. Commercially available graphite nanofibers (GNFs) are used as precursor materials for the synthesis of graphitic nanostacks (GNSs). These materials offer much greater surface area than graphite flakes. Additionally, these materials offer a superior electrical conductivity and a greater average pore size compared to activated carbon electrodes. The state of the art in EC development uses activated carbon (AC) as the electrode material. AC has a high surface area, but its small average pore size inhibits electrolyte ingress/egress. Additionally, AC has a higher resistivity, which generates parasitic heating in high-power applications. This work focuses on fabricating EC from carbon that has a very different structure by increasing the surface area of the GNF by intercalation or exfoliation of the graphitic basal planes. Additionally, various functionalities to the GNS

  9. Multifactorial Experimental Design to Optimize the Anti-Inflammatory and Proangiogenic Potential of Mesenchymal Stem Cell Spheroids.

    Science.gov (United States)

    Murphy, Kaitlin C; Whitehead, Jacklyn; Falahee, Patrick C; Zhou, Dejie; Simon, Scott I; Leach, J Kent

    2017-06-01

    Mesenchymal stem cell therapies promote wound healing by manipulating the local environment to enhance the function of host cells. Aggregation of mesenchymal stem cells (MSCs) into three-dimensional spheroids increases cell survival and augments their anti-inflammatory and proangiogenic potential, yet there is no consensus on the preferred conditions for maximizing spheroid function in this application. The objective of this study was to optimize conditions for forming MSC spheroids that simultaneously enhance their anti-inflammatory and proangiogenic nature. We applied a design of experiments (DOE) approach to determine the interaction between three input variables (number of cells per spheroid, oxygen tension, and inflammatory stimulus) on MSC spheroids by quantifying secretion of prostaglandin E2 (PGE2 ) and vascular endothelial growth factor (VEGF), two potent molecules in the MSC secretome. DOE results revealed that MSC spheroids formed with 40,000 cells per spheroid in 1% oxygen with an inflammatory stimulus (Spheroid 1) would exhibit enhanced PGE2 and VEGF production versus those formed with 10,000 cells per spheroid in 21% oxygen with no inflammatory stimulus (Spheroid 2). Compared to Spheroid 2, Spheroid 1 produced fivefold more PGE2 and fourfold more VEGF, providing the opportunity to simultaneously upregulate the secretion of these factors from the same spheroid. The spheroids induced macrophage polarization, sprout formation with endothelial cells, and keratinocyte migration in a human skin equivalent model-demonstrating efficacy on three key cell types that are dysfunctional in chronic non-healing wounds. We conclude that DOE-based analysis effectively identifies optimal culture conditions to enhance the anti-inflammatory and proangiogenic potential of MSC spheroids. Stem Cells 2017;35:1493-1504. © 2017 AlphaMed Press.

  10. Removal of carbon-14 from irradiated graphite

    Science.gov (United States)

    Dunzik-Gougar, Mary Lou; Smith, Tara E.

    2014-08-01

    Approximately 250,000 tonnes of irradiated graphite waste exists worldwide and that quantity is expected to increase with decommissioning of Generation II reactors and deployment of Generation IV gas-cooled, graphite moderated reactors. This situation indicates the need for a graphite waste management strategy. On of the isotopes of great concern for long-term disposal of irradiated graphite is carbon-14 (14C), with a half-life of 5730 years. Study of irradiated graphite from some nuclear reactors indicates 14C is concentrated on the outer 5 mm of the graphite structure. The aim of the research presented here is to develop a practical method by which 14C can be removed. In parallel with these efforts, the same irradiated graphite material is being characterized to identify the chemical form of 14C in irradiated graphite. A nuclear-grade graphite, NBG-18, and a high-surface-area graphite foam, POCOFoam®, were exposed to liquid nitrogen (to increase the quantity of 14C precursor) and neutron-irradiated (1013 neutrons/cm2/s). During post-irradiation thermal treatment, graphite samples were heated in the presence of an inert carrier gas (with or without the addition of an oxidant gas), which carries off gaseous products released during treatment. Graphite gasification occurs via interaction with adsorbed oxygen complexes. Experiments in argon only were performed at 900 °C and 1400 °C to evaluate the selective removal of 14C. Thermal treatment also was performed with the addition of 3 and 5 vol% oxygen at temperatures 700 °C and 1400 °C. Thermal treatment experiments were evaluated for the effective selective removal of 14C. Lower temperatures and oxygen levels correlated to more efficient 14C removal.

  11. Optimization of Albumin Secretion and Metabolic Activity of Cytochrome P450 1A1 of Human Hepatoblastoma HepG2 Cells in Multicellular Spheroids by Controlling Spheroid Size.

    Science.gov (United States)

    Nishikawa, Tomoko; Tanaka, Yutaro; Nishikawa, Makiya; Ogino, Yuka; Kusamori, Kosuke; Mizuno, Narumi; Mizukami, Yuya; Shimizu, Kazunori; Konishi, Satoshi; Takahashi, Yuki; Takakura, Yoshinobu

    2017-01-01

    Multicellular spheroids are useful as three-dimensional cell culture systems and for cell-based therapies. Their successful application requires an understanding of the consequences of spheroid size for cellular functions. In the present study, we prepared multicellular spheroids of different sizes using the human hepatoblastoma HepG2 cells, as hepatocytes are frequently used for in vitro drug screening and cell-based therapy. Precise polydimethylsiloxane-based microwells with widths of 360, 450, 560, and 770 µm were fabricated using a micromolding technique. Incubation of HepG2 cells in cell culture plates containing the microwells resulted in the formation of HepG2 spheroids with average diameters of 195, 320, 493, and 548 µm. The cell number per spheroid positively correlated with its diameter, and the viability of HepG2 cells was 94% or above for all samples. The smallest HepG2 spheroids showed the highest albumin secretion. On the other hand, the metabolic activity of 7-ethoxyresorufin, a fluorometric substrate for CYP1A1, increased with increasing spheroid size. These results indicate that controlling spheroid size is important when preparing HepG2 spheroids and that the size of HepG2 spheroids greatly influences the cellular function of HepG2 cells in the spheroids.

  12. UVES Abundances of Stars in Nearby Dwarf Spheroidal Galaxies

    Science.gov (United States)

    Tolstoy, Eline; Venn, Kim; Shetrone, Matt; Primas, Francesca; Hill, Vanessa; Kaufer, Andreas; Szeifert, Thomas

    2002-07-01

    It is a truth universally acknowledged, that a galaxy in possession of a good quantity of gas must want to form stars. It is the details of how and why that baffle us all. The simplest theories either would have this process a carefully self-regulated affair, or one that goes completely out of control and is capable of wrecking the galaxy which hosts it. Of course the majority of galaxies seem to amble along somewhere between these two extremes, and the mean properties tend to favour a quiescent self-regulated evolutionary scenario. But there area variety of observations which require us to invoke transitory ‘bursts’ of star-formation at one time or another in most galaxy types. Several nearby dwarf spheroidal galaxies have clearly determined star-formation histories with apparent periods of zero star formation followed by periods of fairly active star formation. If we are able to understand what separated these bursts we would understand several important phenomena in galaxy evolution. Were these galaxies able to clear out their gas reservoir in a burst of star formation? How did this gas return? or did it? Have these galaxies receieved gas from the IGM instead? Could stars from these types of galaxy contribute significantly to the halo population in our Galaxy? To answer these questions we need to combine accurate stellar photometry and Colour-Magnitude Diagram interpretation with detailed metal abundances to combine a star-formation rate versus time with a range of element abundances with time. Different elements trace different evolutionary process (e.g., relative contributions of type I and II supernovae). We often aren't even sure of the abundance spread in these galaxies. We have collected detailed high resolution UVES spectra of four nearby dwarf spheroidal galaxies (Sculptor, Fornax, Leo I & Carina) to begin to answer these questions. This is a precursor study to a more complete study with FLAMES. We presented at this meeting the initial results for

  13. Graphite nanoplatelets produced by oxidation and thermal exfoliation of graphite and electrical conductivities of their epoxy composites.

    Science.gov (United States)

    Raza, Mohsin Ali; Westwood, Aidan; Brown, Andy; Hondow, Nicole; Stirling, Chris

    2012-12-01

    Graphite nanoplatelets were produced by sonication of thermally reduced graphite oxide produced from three precursor graphites. The thicknesses of the resulting graphite nanoplatlets were measured by X-ray diffraction and transmission electron microscopy. The type and size of the precursor graphite plays an important role in the final graphite nanoplatelet quality. The thinnest graphite nanoplatelets (average thickness of 4-7 nm) were obtained from Sri Lankan powdered graphite (average particle size of 0.1-0.2 mm). Thicker graphite nanoplatelets (average thickness of 30-60 nm), were obtained from a Canadian graphite (with an average flake size of 0.5-2 mm). Graphite nanoplatelets obtained by acid intercalation of Sri Lankan graphite were much thicker (an average thickness of 150 nm). Graphite nanoplatelet/epoxy composites containing 4 wt.% graphite nanoplatelets derived from Canadian or Sri Lankan natural graphite have electrical conductivities significantly above the percolation conductivity threshold. In contrast, corresponding composites, produced with (4 wt.%) commercial graphite nanoplatelets, either as-received or re-exfoliated, were electrically insulating. This behaviour is attributed to the highly wrinkled morphology, folded edges and abundant surface functional groups of the commercial graphite nanoplatelets. Thermal reduction of graphite oxide produced from natural flake graphite is therefore a promising route for producing graphite nanoplatelets fillers for electrically-conducting polymer composites.

  14. Fully Automated One-Step Production of Functional 3D Tumor Spheroids for High-Content Screening.

    Science.gov (United States)

    Monjaret, François; Fernandes, Mathieu; Duchemin-Pelletier, Eve; Argento, Amelie; Degot, Sébastien; Young, Joanne

    2016-04-01

    Adoption of spheroids within high-content screening (HCS) has lagged behind high-throughput screening (HTS) due to issues with running complex assays on large three-dimensional (3D) structures.To enable multiplexed imaging and analysis of spheroids, different cancer cell lines were grown in 3D on micropatterned 96-well plates with automated production of nine uniform spheroids per well. Spheroids achieve diameters of up to 600 µm, and reproducibility was experimentally validated (interwell and interplate CV(diameter) integration of micropatterned spheroid models within fundamental research and drug discovery applications.

  15. Oxidation performance of graphite material in reactors

    Institute of Scientific and Technical Information of China (English)

    Xiaowei LUO; Xinli YU; Suyuan YU

    2008-01-01

    Graphite is used as a structural material and moderator for high temperature gas-cooled reactors (HTGR). When a reactor is in operation, graphite oxida-tion influences the safety and operation of the reactor because of the impurities in the coolant and/or the acci-dent conditions, such as water ingress and air ingress. In this paper, the graphite oxidation process is introduced, factors influencing graphite oxidation are analyzed and discussed, and some new directions for further study are pointed out.

  16. Low temperature vapor phase digestion of graphite

    Science.gov (United States)

    Pierce, Robert A.

    2017-04-18

    A method for digestion and gasification of graphite for removal from an underlying surface is described. The method can be utilized to remove graphite remnants of a formation process from the formed metal piece in a cleaning process. The method can be particularly beneficial in cleaning castings formed with graphite molding materials. The method can utilize vaporous nitric acid (HNO.sub.3) or vaporous HNO.sub.3 with air/oxygen to digest the graphite at conditions that can avoid damage to the underlying surface.

  17. The Fracture Toughness of Nuclear Graphites Grades

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, Timothy D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Erdman, III, Donald L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lowden, Rick R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hunter, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hannel, Cara C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-04-01

    New measurements of graphite mode I critical stress intensity factor, KIc (commonly referred to as the fracture toughness) and the mode II critical shear stress intensity, KIIc, are reported and compared with prior data for KIc and KIIc. The new data are for graphite grades PCEA, IG-110 and 2114. Variations of KIc and acoustic emission (AE) data with graphite texture are reported and discussed. The Codes and Standards applications of fracture toughness, KIc, data are also discussed. A specified minimum value for nuclear graphite KIc is recommended.

  18. AC induction field heating of graphite foam

    Energy Technology Data Exchange (ETDEWEB)

    Klett, James W.; Rios, Orlando; Kisner, Roger

    2017-08-22

    A magneto-energy apparatus includes an electromagnetic field source for generating a time-varying electromagnetic field. A graphite foam conductor is disposed within the electromagnetic field. The graphite foam when exposed to the time-varying electromagnetic field conducts an induced electric current, the electric current heating the graphite foam. An energy conversion device utilizes heat energy from the heated graphite foam to perform a heat energy consuming function. A device for heating a fluid and a method of converting energy are also disclosed.

  19. Nickel coated graphite fiber conductive composites

    Energy Technology Data Exchange (ETDEWEB)

    Evans, R.E.; Hall, D.E.; Luxon, B.A.

    1986-07-01

    Nickel coated graphite (NCG) fiber, consisting of a thin continuous plating of high purity nickel over an aerospace-grade graphite core, offers performance added features by combining the lightweight and high structural reinforcement of graphite fiber with the thermal and electrical conductivity of nickel. These NCG filaments, which are composite constructions in their own right, can be processed and impregnated with thermosetting or thermoplastic resins in the same manner that graphite fiber tows are processed and impregnated to produce roving, tape or fabric prepreg. Therefore, NCG fibers can be readily integrated into structural laminate assemblies using established composites-manufacturing practices.

  20. Identification of Lgr5-Independent Spheroid-Generating Progenitors of the Mouse Fetal Intestinal Epithelium

    Directory of Open Access Journals (Sweden)

    Roxana C. Mustata

    2013-10-01

    Full Text Available Immortal spheroids were generated from fetal mouse intestine using the culture system initially developed to culture organoids from adult intestinal epithelium. Spheroid proportion progressively decreases from fetal to postnatal period, with a corresponding increase in production of organoids. Like organoids, spheroids show Wnt-dependent indefinite self-renewing properties but display a poorly differentiated phenotype reminiscent of incompletely caudalized progenitors. The spheroid transcriptome is strikingly different from that of adult intestinal stem cells, with minimal overlap of Wnt target gene expression. The receptor LGR4, but not LGR5, is essential for their growth. Trop2/Tacstd2 and Cnx43/Gja1, two markers highly enriched in spheroids, are expressed throughout the embryonic-day-14 intestinal epithelium. Comparison of in utero and neonatal lineage tracing using Cnx43-CreER and Lgr5-CreERT2 mice identified spheroid-generating cells as developmental progenitors involved in generation of the prenatal intestinal epithelium. Ex vivo, spheroid cells have the potential to differentiate into organoids, qualifying as a fetal type of intestinal stem cell.

  1. A comparison between semi-spheroid- and dome-shaped quantum dots coupled to wetting layer

    Directory of Open Access Journals (Sweden)

    Mohammadreza Shahzadeh

    2014-06-01

    Full Text Available During the epitaxial growth method, self-assembled semi-spheroid-shaped quantum dots (QDs are formed on the wetting layer (WL. However for sake of simplicity, researchers sometimes assume semi-spheroid-shaped QDs to be dome-shaped (hemisphere. In this work, a detailed and comprehensive study on the difference between electronic and transition properties of dome- and semi-spheroid-shaped quantum dots is presented. We will explain why the P-to-S intersubband transition behaves the way it does. The calculated results for intersubband P-to-S transition properties of quantum dots show two different trends for dome-shaped and semi-spheroid-shaped quantum dots. The results are interpreted using the probability of finding electron inside the dome/spheroid region, with emphasis on the effects of wetting layer. It is shown that dome-shaped and semi-spheroid-shaped quantum dots feature different electronic and transition properties, arising from the difference in lateral dimensions between dome- and semi-spheroid-shaped QDs. Moreover, an analogy is presented between the bound S-states in the quantum dots and a simple 3D quantum mechanical particle in a box, and effective sizes are calculated. The results of this work will benefit researchers to present more realistic models of coupled QD/WL systems and explain their properties more precisely.

  2. Early formation of massive, compact, spheroidal galaxies with classical profiles by violent disc instability or mergers

    CERN Document Server

    Ceverino, Daniel; Tweed, Dylan; Primack, Joel

    2014-01-01

    We address the formation of massive stellar spheroids between redshifts $z=4$ and 1 using a suite of AMR hydro-cosmological simulations. The spheroids form as bulges, and the spheroid mass growth is partly driven by violent disc instability (VDI) and partly by mergers. A kinematic decomposition to disc and spheroid yields that the mass fraction in the spheroid is between 50% and 90% and is roughly constant in time, consistent with a cosmological steady state of VDI discs that are continuously fed from the cosmic web. The density profile of the spheroid is typically classical, with a Sersic index $n = 4.5\\pm 1$, independent of whether it grew by mergers or VDI. The disc is characterized by $n=1.5\\pm 0.5$, and the whole galaxy by $n=3\\pm 1$. The high-redshift spheroids are compact due to the dissipative inflow of gas and the high universal density. The stellar surface density within the effective radius of each galaxy as it evolves remains roughly constant in time after its first growth. For galaxies of a fixed...

  3. Evaluation of bioactivity of octacalcium phosphate using osteoblastic cell aggregates on a spheroid culture device

    Directory of Open Access Journals (Sweden)

    Takahisa Anada

    2016-03-01

    Full Text Available Much attention has been paid to three-dimensional cell culture systems in the field of regenerative medicine, since three-dimensional cellular aggregates, or spheroids, are thought to better mimic the in vivo microenvironments compared to conventional monolayer cultured cells. Synthetic calcium phosphate (CaP materials are widely used as bone substitute materials in orthopedic and dental surgeries. Here we have developed a technique for constructing a hybrid spheroid consisting of mesenchymal stem cells (MSCs and synthetic CaP materials using a spheroid culture device. We found that the device is able to generate uniform-sized CaP/cell hybrid spheroids rapidly and easily. The results showed that the extent of osteoblastic differentiation from MSCs was different when cells were grown on octacalcium phosphate (OCP, hydroxyapatite (HA, or β-tricalcium phosphate (β-TCP. OCP showed the greatest ability to increase the alkaline phosphatase activity of the spheroid cells. The results suggest that the spheroids with incorporated OCP may be an effective implantable hybrid consisting of scaffold material and cells for bone regeneration. It is also possible that this CaP–cell spheroid system may be used as an in vitro method for assessing the osteogenic induction ability of CaP materials.

  4. Isolation, identification, and spheroids formation of breast cancer stem cells, therapeutics implications

    Directory of Open Access Journals (Sweden)

    Maytham Abbas Abboodi

    2014-01-01

    Full Text Available Aims: Cancer stem cells (CSCs are population of cells present in tumors, which can undergo self-renewal and differentiation. Three-dimensional (3D in vitro models mimic features of the in vivo environment and provide unique perspectives on the behavior of stem cells. Materials and Methods: In this study, MDA-MB 231 cells were grown in two-dimensional (2D monolayers and 3D spheroid formats and CSCs were isolated and grown as spheroids. The isolated CSCs were subjected to molecular studies for detection of CD44, CD24, MMP1, ABCG2, ALDH1, and GAPDH markers. Results: The monolayer of CSCs grown as spheroids showed better growth rate than the MDA-MB 231 cells, which shows the efficacy of 3D spheroid format of growing CSCs. CD44 show increased expression in spheroids compared to 2D culture of MDA-MB 231. ALDH1 a key marker of breast stem cells was highly expressed in BCSCs and MDA-MB 231 grown in 3D, while being absent in CSCs and MDA-MB 231 cells grown in 2D. Conclusions: The CSCs grown as spheroids showed better growth rate, which showed the efficacy of 3D spheroid format for CSCs culture. Since the association between BCSCs prevalence and clinical outcome and the evidence presented in this study support key roles of CSCs in breast cancer metastasis and drug resistance, it has been proposed that new therapies must target these cells.

  5. Encapsulated multicellular tumor spheroids as a novel in vitro model to study small size tumors

    Directory of Open Access Journals (Sweden)

    Markvicheva Elena

    2003-01-01

    Full Text Available Presently multicellular tumor spheroids (MTS are being widely used in various aspects of tumor biology, including studies in biology and photodynamic therapy. The cellular organization of spheroids allows the recreation of in vivo small tumors much better than all common two-dimensional in vitro models. The cell encapsulation method could be proposed as a novel technique to quickly and easily prepare a large number of spheroids with narrow size distribution within a desirable diameter range. Moreover, the proposed technique for spheroid generation using encapsulated growing tumor cells could provide entirely new avenues to develop a novel spheroid co-culture model (for instance, the in vitro co-cultvation of tumor cells and monocytes, or epithelial cells, or fibroblasts etc. The current research was aimed at developing a simple and reliable method to encapsulate tumor cells and to cultivate them in vitro. In order to generate spheroids, MCF-7 cells were encapsulated and cultivated in 200 ml T-flasks in a 5% CO2 atmosphere at 37°C for 4-5 weeks. The cell proliferation was easily observed using a light microscope. The cells grew in aggregates increasing in size with time. The cell growth resulted in the formation of large cell clusters (spheroids which filled the whole microcapsule volume in 4-5 weeks.

  6. Electromagnetic scattering by spheroidal volumes of discrete random medium

    Science.gov (United States)

    Mishchenko, Michael I.; Dlugach, Janna M.

    2017-10-01

    We use the superposition T-matrix method to compare the far-field scattering matrices generated by spheroidal and spherical volumes of discrete random medium having the same volume and populated by identical spherical particles. Our results fully confirm the robustness of the previously identified coherent and diffuse scattering regimes and associated optical phenomena exhibited by spherical particulate volumes and support their explanation in terms of the interference phenomenon coupled with the order-of-scattering expansion of the far-field Foldy equations. We also show that increasing nonsphericity of particulate volumes causes discernible (albeit less pronounced) optical effects in forward and backscattering directions and explain them in terms of the same interference/multiple-scattering phenomenon.

  7. Spheroid degeneration of conjunctiva and cornea. Two years' follow up.

    Science.gov (United States)

    Norn, M

    1980-10-01

    Twenty-six subjects with spheroid degeneration were followed up after two years. The number of colourless conjunctival droplets was seen to have increased by on an average 46% (2 alpha = 0.05) and that of autofluorescent conjunctival droplets by 223% (2 alpha less than 0.01). Counting within the individual sites sites disclosed that some droplets will disappear (not less than 30 and 21% respectivelY), while recently formed will constitute at least 76 and 243%. The number of areas with band-shaped keratopathy was found to rise from 3 to 26 (P less than 0.001) out of 104 possibilities, (nasally and temporally of right and left eye). Vital staining (fluorescein, rose bengal, tetrazolium, alcian blue) showed the epithelium above the droplets to be intact, and the droplet-containing eyes were found not to be abnormally dry (break up time, tear production).

  8. The influence of binary stars on dwarf spheroidal galaxy kinematics

    CERN Document Server

    Hargreaves, J C; Annan, J D

    1995-01-01

    We have completed a Monte-Carlo simulation to estimate the effect of binary star orbits on the measured velocity dispersion in dwarf spheroidal galaxies. This paper analyses previous attempts at this calculation, and explains the simulations which were performed with mass, period and ellipticity distributions similar to that measured for the solar neighbourhood. The conclusion is that with functions such as these, the contribution of binary stars to the velocity dispersion is small. The distributions are consistent with the percentage of binaries detected by observations, although this is quite dependent on the measuring errors and on the number of years over which measurements have been taken. For binaries to be making a significant contribution to the dispersion measured in dSph galaxies, the distributions of the orbital parameters would need to be very different from those of stars in the solar neighbourhood. In particular more smaller period orbits with higher mass secondaries would be required. The shape...

  9. Eigenvalue spectrum of the spheroidal harmonics: A uniform asymptotic analysis

    Science.gov (United States)

    Hod, Shahar

    2015-06-01

    The spheroidal harmonics Slm (θ ; c) have attracted the attention of both physicists and mathematicians over the years. These special functions play a central role in the mathematical description of diverse physical phenomena, including black-hole perturbation theory and wave scattering by nonspherical objects. The asymptotic eigenvalues {Alm (c) } of these functions have been determined by many authors. However, it should be emphasized that all the previous asymptotic analyzes were restricted either to the regime m → ∞ with a fixed value of c, or to the complementary regime | c | → ∞ with a fixed value of m. A fuller understanding of the asymptotic behavior of the eigenvalue spectrum requires an analysis which is asymptotically uniform in both m and c. In this paper we analyze the asymptotic eigenvalue spectrum of these important functions in the double limit m → ∞ and | c | → ∞ with a fixed m / c ratio.

  10. Eigenvalue spectrum of the spheroidal harmonics: A uniform asymptotic analysis

    CERN Document Server

    Hod, Shahar

    2015-01-01

    The spheroidal harmonics $S_{lm}(\\theta;c)$ have attracted the attention of both physicists and mathematicians over the years. These special functions play a central role in the mathematical description of diverse physical phenomena, including black-hole perturbation theory and wave scattering by nonspherical objects. The asymptotic eigenvalues $\\{A_{lm}(c)\\}$ of these functions have been determined by many authors. However, it should be emphasized that all previous asymptotic analyzes were restricted either to the regime $m\\to\\infty$ with a fixed value of $c$, or to the complementary regime $|c|\\to\\infty$ with a fixed value of $m$. A fuller understanding of the asymptotic behavior of the eigenvalue spectrum requires an analysis which is asymptotically uniform in both $m$ and $c$. In this paper we analyze the asymptotic eigenvalue spectrum of these important functions in the double limit $m\\to\\infty$ and $|c|\\to\\infty$ with a fixed $m/c$ ratio.

  11. Landslides and Mass Shedding on Spinning Spheroidal Asteroids

    CERN Document Server

    Scheeres, D J

    2014-01-01

    Conditions for regolith landslides to occur on spinning, gravitating spheroidal asteroids and their aftermath are studied. These conditions are developed by application of classical granular mechanics stability analysis to the asteroid environment. As part of our study we determine how slopes evolve across the surface of these bodies as a function of spin rate, the dynamical fate of material that exceeds the angle of repose, and an analysis of how the shape of the body may be modified based on these results. We find specific characteristics for body surfaces and shapes when spun near the surface disruption limit and develop what their observable implications are. The small, oblate and rapidly spinning asteroids such as 1999 KW4 Alpha and 2008 EV5 exhibit some of these observable traits. The detailed mechanisms outlined here can also provide insight and constraints on the recently observed active asteroids such as P/2013 P5, and the creation of asteroidal meteor streams.

  12. A theoretical study of the spheroidal droplet evaporation in forced convection

    Science.gov (United States)

    Li, Jie; Zhang, Jian

    2014-11-01

    In many applications, the shape of a droplet may be assumed to be an oblate spheroid. A theoretical study is conducted on the evaporation of an oblate spheroidal droplet under forced convection conditions. Closed-form analytical expressions of the mass evaporation rate for an oblate spheroid are derived, in the regime of controlled mass-transfer and heat-transfer, respectively. The variation of droplet size during the evaporation process is presented in the regime of shrinking dynamic model. Comparing with the droplets having the same surface area, an increase in the aspect ratio enhances the mass evaporation rate and prolongs the burnout time.

  13. Motion of a rigid prolate spheroid in a sound wave field.

    Science.gov (United States)

    Zhou, Hongkun; Hong, Lianjin

    2014-08-01

    The motions of a rigid and unconstrained prolate spheroid subjected to plane sound waves are computed using preliminary analytic derivation and numerical approach. The acoustically induced motions are found comprising torsional motion as well as translational motion in the case of acoustic oblique incidence and present great relevance to the sound wavelength, body geometry, and density. The relationship between the motions and acoustic particle velocity is obtained through finite element simulation in terms of sound wavelengths much longer than the overall size of the prolate spheroid. The results are relevant to the design of inertial acoustic particle velocity sensors based on prolate spheroids.

  14. Shape effects on dynamics of inertia-free spheroids in wall turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Challabotla, Niranjan Reddy; Zhao, Lihao; Andersson, Helge I. [Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway)

    2015-06-15

    The rotational motion of inertia-free spheroids has been studied in a numerically simulated turbulent channel flow. Although inertia-free spheroids were translated as tracers with the flow, neither the disk-like nor the rod-like particles adapted to the fluid rotation. The flattest disks preferentially aligned their symmetry axes normal to the wall, whereas the longest rods were parallel with the wall. The shape-dependence of the particle orientations carried over to the particle rotation such that the mean spin was reduced with increasing departure from sphericity. The streamwise spin fluctuations were enhanced due to asphericity, but substantially more for prolate than for oblate spheroids.

  15. Solution of Axisymmetric Potential Problem in Oblate Spheroid Using the Exodus Method

    Directory of Open Access Journals (Sweden)

    O. D. Momoh

    2014-01-01

    Full Text Available This paper presents the use of Exodus method for computing potential distribution within a conducting oblate spheroidal system. An explicit finite difference method for solving Laplace’s equation in oblate spheroidal coordinate systems for an axially symmetric geometry was developed. This was used to determine the transition probabilities for the Exodus method. A strategy was developed to overcome the singularity problems encountered in the oblate spheroid pole regions. The potential computation results obtained correlate with those obtained by exact solution and explicit finite difference methods.

  16. Leukoencephalopathy with spheroids (HDLS) and pigmentary leukodystrophy (POLD): a single entity?

    Science.gov (United States)

    Wider, C; Van Gerpen, J A; DeArmond, S; Shuster, E A; Dickson, D W; Wszolek, Z K

    2009-06-02

    Hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) and familial pigmentary orthochromatic leukodystrophy (POLD) present as adult-onset dementia with motor impairment and epilepsy. They are regarded as distinct diseases. We review data from the literature that support their being a single entity. Apart from a slightly older age at onset, a more rapid course, and more prominent pyramidal tract involvement, familial POLD is clinically similar to HDLS. Moreover, the pathologic hallmarks of the two diseases, axonal spheroids in HDLS and pigmented macrophages in POLD, can be identified in both conditions. This supports HDLS and POLD being referred collectively as adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP).

  17. Electronic structure of graphite; Elektronische Struktur von Graphit

    Energy Technology Data Exchange (ETDEWEB)

    Alsheimer, W.

    2000-07-01

    In an all-electron calculation ab initio the electronic properties of graphite in the ground state were self-consistently determined by means of the MAPW procedure in warped-muffin-tin approximation. many- particle effects were regarded in the framework of the density- functional theory in the parametrization of the local density approximation of Hedin and Lundqvist. Starting from the determined self-consistent one-particle potential via the Fourier transformed of the Bloch wave functions the electronic momentum densities perpendicular and parallel to the layer-planes of all occupied states of graphite were calculated and compared with newer experimental and theoretical values. The special approach of the MAPW mehtod guarantees continuousness of the wave function and its first derivative in the whole Wigner-Seitz cell and by this a fast decreasement of the Fourier coefficients. This fact was used for the calculation of the easily accessible Compton profiles, which represent an integration over all components of the momentum density in the crystal direction of interest. These results, especially the anisotropic Compton profile, were also compared with experimental works and other calculations.

  18. Analysis of Wigner energy release process in graphite stack of shut-down uranium-graphite reactor

    OpenAIRE

    Bespala, E. V.; Pavliuk, A. O.; Kotlyarevskiy, S. G.

    2015-01-01

    Data, which finding during thermal differential analysis of sampled irradiated graphite are presented. Results of computational modeling of Winger energy release process from irradiated graphite staking are demonstrated. It's shown, that spontaneous combustion of graphite possible only in adiabatic case.

  19. Significance of primary irradiation creep in graphite

    CSIR Research Space (South Africa)

    Erasmus, C

    2013-05-01

    Full Text Available Traditionally primary irradiation creep is introduced into graphite analysis by applying the appropriate amount of creep strain to the model at the initial time-step. This is valid for graphite components that are subjected to high fast neutron flux...

  20. Structure-Property Relationships in Intercalated Graphite.

    Science.gov (United States)

    1985-07-10

    and . vermicular graphite host materials. Detailed TEM results show that the glassy phase is induced by the electron beam irradiation through a...sample thickness could be related to the observation of a glass phase, experiments were carried out using both kish and vermicular graphite host materials

  1. Tire containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2011-01-01

    A tire, tire lining or inner tube, containing a polymer composite, made of at least one rubber and/or at least one elastomer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g.

  2. Inhibition of Oxidation in Nuclear Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Phil Winston; James W. Sterbentz; William E. Windes

    2013-10-01

    Graphite is a fundamental material of high temperature gas cooled nuclear reactors, providing both structure and neutron moderation. Its high thermal conductivity, chemical inertness, thermal heat capacity, and high thermal structural stability under normal and off normal conditions contribute to the inherent safety of these reactor designs. One of the primary safety issues for a high temperature graphite reactor core is the possibility of rapid oxidation of the carbon structure during an off normal design basis event where an oxidizing atmosphere (air ingress) can be introduced to the hot core. Although the current Generation IV high temperature reactor designs attempt to mitigate any damage caused by a postualed air ingress event, the use of graphite components that inhibit oxidation is a logical step to increase the safety of these reactors. Recent experimental studies of graphite containing between 5.5 and 7 wt% boron carbide (B4C) indicate that oxidation is dramatically reduced even at prolonged exposures at temperatures up to 900°C. The proposed addition of B4C to graphite components in the nuclear core would necessarily be enriched in B-11 isotope in order to minimize B-10 neutron absorption and graphite swelling. The enriched boron can be added to the graphite during billet fabrication. Experimental oxidation rate results and potential applications for borated graphite in nuclear reactor components will be discussed.

  3. Hydrogen storage in graphite nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Park, C.; Tan, C.D.; Hidalgo, R.; Baker, R.T.K.; Rodriguez, N.M. [Northeastern Univ., Boston, MA (United States). Chemistry Dept.

    1998-08-01

    Graphite nanofibers (GNF) are a type of material that is produced by the decomposition of carbon containing gases over metal catalyst particles at temperatures around 600 C. These molecularly engineered structures consist of graphene sheets perfectly arranged in a parallel, perpendicular or at angle orientation with respect to the fiber axis. The most important feature of the material is that only edges are exposed. Such an arrangement imparts the material with unique properties for gas adsorption because the evenly separated layers constitute the most ordered set of nanopores that can accommodate an adsorbate in the most efficient manner. In addition, the non-rigid pore walls can also expand so as to accommodate hydrogen in a multilayer conformation. Of the many varieties of structures that can be produced the authors have discovered that when gram quantities of a selected number of GNF are exposed to hydrogen at pressures of {approximately} 2,000 psi, they are capable of adsorbing and storing up to 40 wt% of hydrogen. It is believed that a strong interaction is established between hydrogen and the delocalized p-electrons present in the graphite layers and therefore a new type of chemistry is occurring within these confined structures.

  4. Fiber release characteristics of graphite hybrid composites

    Science.gov (United States)

    Henshaw, J.

    1980-01-01

    The paper considers different material concepts that can be fabricated of hybridized composites which demonstrate improved graphite fiber retention capability in a severe fire without significant reduction to the composite properties. More than 30 panels were fabricated for mechanical and fire tests, the details and results of which are presented. Methods of composite hybridization investigated included the addition of oxidation resistant fillers to the resin, mechanically interlocking the graphite fibers by the use of woven fabrics, and the addition of glass fibers and glass additives designed to melt and fuse the graphite fibers together. It is concluded that a woven fabric with a serving of glass around each graphite tow is by far the superior of those evaluated: not only is there a coalescing effect in each graphite layer, but there is also a definite adhesion of each layer to its neighbor.

  5. Significance of primary irradiation creep in graphite

    Energy Technology Data Exchange (ETDEWEB)

    Erasmus, Christiaan, E-mail: christiaan.erasmus@gmail.com [Pebble Bed Modular Reactor (Proprietary) Limited, PO Box 9396, Centurion 0046 (South Africa); Kok, Schalk [Advanced Mathematical Modelling, CSIR Modelling and Digital Science, Pretoria 0001 (South Africa); Hindley, Michael P. [Pebble Bed Modular Reactor (Proprietary) Limited, PO Box 9396, Centurion 0046 (South Africa)

    2013-05-15

    Traditionally primary irradiation creep is introduced into graphite analysis by applying the appropriate amount of creep strain to the model at the initial time-step. This is valid for graphite components that are subjected to high fast neutron flux fields and constant stress fields, but it does not allow for the effect of movement of stress locations around a graphite component during life, nor does it allow primary creep to be applied rate-dependently to graphite components subject to lower fast neutron flux. This paper shows that a differential form of primary irradiation creep in graphite combined with the secondary creep formulation proposed by Kennedy et al. performs well when predicting creep behaviour in experimental samples. The significance of primary irradiation creep in particular in regions with lower flux is investigated. It is shown that in low flux regions with a realistic operating lifetime primary irradiation creep is significant and is larger than secondary irradiation creep.

  6. Damping behavior of synthetic graphite beams

    Directory of Open Access Journals (Sweden)

    Luiz Cláudio Pardini

    2006-06-01

    Full Text Available The main objective of this work was to obtain the damping factor (xi as well as the elasticity modulus (E of two kinds of synthetic graphite (HLM and ATJ, using the modal analysis technique. Prismatic beams of square section (~ 11 x 11 mm and length over thickness ratio (L/t of about 22.7 were tested in the free - free boundary condition. The first four modes of vibration were taken into account in the non-destructive evaluation of the materials. In addition, numerical simulations were also carried out in this investigation. The agreement between the theoretical and the experimental results was quite good. The average values of E and xi for the HLM graphite were 20% and 90% higher, respectively, than those presented by the ATJ graphite, indicating that the HLM graphite has, proportionally, more damping mechanisms than the ATJ graphite.

  7. Axisymmetric scattering of an acoustical Bessel beam by a rigid fixed spheroid

    CERN Document Server

    Mitri, F G

    2015-01-01

    Based on the partial-wave series expansion (PWSE) method in spherical coordinates, a formal analytical solution for the acoustic scattering of a zeroth-order Bessel acoustic beam centered on a rigid fixed (oblate or prolate) spheroid is provided. The unknown scattering coefficients of the spheroid are determined by solving a system of linear equations derived for the Neumann boundary condition. Numerical results for the modulus of the backscattered pressure (\\theta = \\pi) in the near-field and the backscattering form function in the far-field for both prolate and oblate spheroids are presented and discussed, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid), the half-cone angle of the Bessel beam \\beta, and the dimensionless frequency. The plots display periodic oscillations (versus the dimensionless frequency) due to the interference of specularly reflected waves in the backscattering direction with circumferential Franz' waves circumnavigati...

  8. Green's function and image system for the Laplace operator in the prolate spheroidal geometry

    Science.gov (United States)

    Xue, Changfeng; Deng, Shaozhong

    2017-01-01

    In the present paper, electrostatic image theory is studied for Green's function for the Laplace operator in the case where the fundamental domain is either the exterior or the interior of a prolate spheroid. In either case, an image system is developed to consist of a point image inside the complement of the fundamental domain and an additional symmetric continuous surface image over a confocal prolate spheroid outside the fundamental domain, although the process of calculating such an image system is easier for the exterior than for the interior Green's function. The total charge of the surface image is zero and its centroid is at the origin of the prolate spheroid. In addition, if the source is on the focal axis outside the prolate spheroid, then the image system of the exterior Green's function consists of a point image on the focal axis and a line image on the line segment between the two focal points.

  9. Study of human prostate spheroids treated with zinc using X-ray microfluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Leitao, Roberta G.; Lopes, Ricardo T.; Pereira, Gabriela R., E-mail: roberta@lin.ufrj.br, E-mail: gpereira@metalmat.ufrj.br [Coordenacao dos Cursos de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Santos, Carlos A.N., E-mail: cansantos.bio@gmail.com [Instituto Nacional de Metrologia, Qualidade e Tecnologia (DIPRO/INMETRO), Duque de Caxias, RJ (Brazil). Lab. de Biotecnologia; Palumbo Junior, Antonio; Nasciutti, Luiz E., E-mail: nasciutt@ufrj.br [Universidade Federal do Rio de Janeiro (ICB/CCS/UFRJ), Rio de Janeiro, RJ (Brazil). Lab. de Interacoes Celulares; Souza, Pedro A.V.R., E-mail: pedroaugustoreis@uol.com.br [Hospital Federal do Andarai (HFA), Rio de Janeiro, RJ (Brazil). Servico de Urologia; Anjos, Marcelino J., E-mail: marcelin@lin.ufrj.br [Universidade Estatual do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil). Inst. de Fisica

    2013-07-01

    Spheroids cell culture is a useful technique for tissue engineering or regenerative medicine re-search, pharmacological and toxicological studies, and fundamental studies in cell biology. In this study, we investigated Zn distribution in cell spheroids in benign prostate hyperplasia (BPH) and prostate cancer (DU145) and analyzed the differences in the response to Zinc (0-150 μM) treatment. The measurements were performed in standard geometry of 45 deg incidence, exciting with a white beam and using an optical capillary with 20 μm diameter collimation in the XRF beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). The results showed non-uniform distribution of Zn in all the spheroids analyzed. The differential response to zinc of DU145 and BPH cell spheroids suggests that zinc may have an important role in prostate cancer and BPH diagnosis. (author)

  10. Patient-specific three-dimensional explant spheroids derived from human nasal airway epithelium

    DEFF Research Database (Denmark)

    Marthin, June Kehlet; Stevens, Elizabeth Munkebjerg; Larsen, Lars Allan

    2017-01-01

    BACKGROUND: Three-dimensional explant spheroid formation is an ex vivo technique previously used in studies of airway epithelial ion and water transport. Explanted cells and sheets of nasal epithelium form fully differentiated spheroids enclosing a partly fluid-filled lumen with the ciliated apical....... Nasal ciliary cells and sheets were removed on day 1 by nasal brush biopsy and analyzed with regard to ciliary beat pattern-and frequency using high-speed video imaging for standard reference values. Three-dimensional explant spheroid formation was initiated in the same individual on the same day...... was successful in 15 out of 18 (82%) sampled individuals. Thus, formation was successful in seven healthy controls and eight PCD patients, while unsuccessful in 3 with PCD due to infection. Median (range) number of days in culture before harvesting of spheroids was 4 (1-5) in healthy versus 2 (1-5) in PCD...

  11. Surface chemistry-mediated penetration and gold nanorod thermotherapy in multicellular tumor spheroids

    Science.gov (United States)

    Jin, Shubin; Ma, Xiaowei; Ma, Huili; Zheng, Kaiyuan; Liu, Juan; Hou, Shuai; Meng, Jie; Wang, Paul C.; Wu, Xiaochun; Liang, Xing-Jie

    2012-12-01

    We investigated the penetration and thermotherapy efficiency of different surface coated gold nanorods (Au NRs) in multicellular tumor spheroids. The current data show that negatively charged Au NRs, other than positively charged Au NRs, can penetrate deep into the tumor spheroids and achieve a significant thermal therapeutic benefit.We investigated the penetration and thermotherapy efficiency of different surface coated gold nanorods (Au NRs) in multicellular tumor spheroids. The current data show that negatively charged Au NRs, other than positively charged Au NRs, can penetrate deep into the tumor spheroids and achieve a significant thermal therapeutic benefit. Electronic supplementary information (ESI) available: Materials and methods section. See DOI: 10.1039/c2nr31877f

  12. Inversion of spheroid particle size distribution in wider size range and aspect ratio range

    Directory of Open Access Journals (Sweden)

    Tang Hong

    2013-01-01

    Full Text Available The non-spherical particle sizing is very important in the aerosol science, and it can be determined by the light extinction measurement. This paper studies the effect of relationship of the size range and aspect ratio range on the inversion of spheroid particle size distribution by the dependent mode algorithm. The T matrix method and the geometric optics approximation method are used to calculate the extinction efficiency of the spheroids with different size range and aspect ratio range, and the inversion of spheroid particle size distribution in these different ranges is conducted. Numerical simulation indicates that a fairly reasonable representation of the spheroid particle size distribution can be obtained when the size range and aspect ratio range are suitably chosen.

  13. Spheroids at the Cretaceous-Tertiary boundary are altered impact droplets of basaltic composition

    Energy Technology Data Exchange (ETDEWEB)

    Montanari, A.; Hay, R.L.; Alvarez, W.; Asaro, F.; Michel, H.V.; Alvarez, L.W.; Smit, J.

    1983-11-01

    Sand-size spheroids of K-feldspar in the Cretaceous-Tertiary (C-T) boundary clay at Caravaca, southern Spain, were interpreted by Smit and Klaver as having solidified from a melt resulting from the impact of a large extraterrestrial body. Sand-size spheroids of K-feldspar, glauconite, and magnetite-quartz have been found in the C-T boundary clay in northern Italy, and spheroids of K-feldspar and pyrite were found in the boundary clay at Deep Sea Drilling Project Site 465A, in the central Pacific. These spheroids have textures similar to those of rapidly crystallized feldspar and mafic silicates. They are interpreted as diagenetically altered microcrystalline spherules of basaltic composition produced by the impact of a large asteroid in an ocean basin at the end of the Cretaceous. They are analogous to the glassy microtektites produced by impacts on more siliceous target rocks. 21 references, 4 figures.

  14. Genetics Home Reference: adult-onset leukoencephalopathy with axonal spheroids and pigmented glia

    Science.gov (United States)

    ... with spheroids (HDLS) and familial pigmentary orthochromatic leukodystrophy (POLD), both of which cause very similar white matter damage and cognitive and movement problems. POLD was thought to be distinguished by the presence ...

  15. Spheroid culture as a tool for creating 3D complex tissues.

    Science.gov (United States)

    Fennema, Eelco; Rivron, Nicolas; Rouwkema, Jeroen; van Blitterswijk, Clemens; de Boer, Jan

    2013-02-01

    3D cell culture methods confer a high degree of clinical and biological relevance to in vitro models. This is specifically the case with the spheroid culture, where a small aggregate of cells grows free of foreign materials. In spheroid cultures, cells secrete the extracellular matrix (ECM) in which they reside, and they can interact with cells from their original microenvironment. The value of spheroid cultures is increasing quickly due to novel microfabricated platforms amenable to high-throughput screening (HTS) and advances in cell culture. Here, we review new possibilities that combine the strengths of spheroid culture with new microenvironment fabrication methods that allow for the creation of large numbers of highly reproducible, complex tissues.

  16. Modeling Fission Product Sorption in Graphite Structures

    Energy Technology Data Exchange (ETDEWEB)

    Szlufarska, Izabela [University of Wisconsin, Madison, WI (United States); Morgan, Dane [University of Wisconsin, Madison, WI (United States); Allen, Todd [University of Wisconsin, Madison, WI (United States)

    2013-04-08

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high- temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission

  17. AGC-2 Graphite Preirradiation Data Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    William Windes; W. David Swank; David Rohrbaugh; Joseph Lord

    2013-08-01

    This report described the specimen loading order and documents all pre-irradiation examination material property measurement data for the graphite specimens contained within the second Advanced Graphite Capsule (AGC-2) irradiation capsule. The AGC-2 capsule is the second in six planned irradiation capsules comprising the Advanced Graphite Creep (AGC) test series. The AGC test series is used to irradiate graphite specimens allowing quantitative data necessary for predicting the irradiation behavior and operating performance of new nuclear graphite grades to be generated which will ascertain the in-service behavior of the graphite for pebble bed and prismatic Very High Temperature Reactor (VHTR) designs. Similar to the AGC-1 specimen pre-irradiation examination report, material property tests were conducted on specimens from 18 nuclear graphite types but on an increased number of specimens (512) prior to loading into the AGC-2 irradiation assembly. All AGC-2 specimen testing was conducted at Idaho National Laboratory (INL) from October 2009 to August 2010. This report also details the specimen loading methodology for the graphite specimens inside the AGC-2 irradiation capsule. The AGC-2 capsule design requires “matched pair” creep specimens that have similar dose levels above and below the neutron flux profile mid-plane to provide similar specimens with and without an applied load. This document utilized the neutron flux profile calculated for the AGC-2 capsule design, the capsule dimensions, and the size (length) of the selected graphite and silicon carbide samples to create a stacking order that can produce “matched pairs” of graphite samples above and below the AGC-2 capsule elevation mid-point to provide specimens with similar neutron dose levels.

  18. Direct Measurements of Oxygen Gradients in Spheroid Culture System Using Electron Parametric Resonance Oximetry.

    Directory of Open Access Journals (Sweden)

    Laura M Langan

    Full Text Available Advanced in vitro culture from tissues of different origin includes three-dimensional (3D organoid micro structures that may mimic conditions in vivo. One example of simple 3D culture is spheroids; ball shaped structures typically used as liver and tumour models. Oxygen is critically important in physiological processes, but is difficult to quantify in 3D culture: and the question arises, how small does a spheroid have to be to have minimal micro-environment formation? This question is of particular importance in the growing field of 3D based models for toxicological assessment. Here, we describe a simple non-invasive approach modified for the quantitative measurement and subsequent evaluation of oxygen gradients in spheroids developed from a non-malignant fish cell line (i.e. RTG-2 cells using Electron Paramagnetic Resonance (EPR oximetry. Sonication of the paramagnetic probe Lithium phthalocyanine (LiPc allows for incorporation of probe particulates into spheroid during its formation. Spectra signal strength after incorporation of probe into spheroid indicated that a volume of 20 μl of probe (stock solution: 0.10 mg/mL is sufficient to provide a strong spectra across a range of spheroid sizes. The addition of non-toxic probes (that do not produce or consume oxygen report on oxygen diffusion throughout the spheroid as a function of size. We provide evidence supporting the use of this model over a range of initial cell seeding densities and spheroid sizes with the production of oxygen distribution as a function of these parameters. In our spheroid model, lower cell seeding densities (∼2,500 cells/spheroid and absolute size (118±32 μm allow control of factors such as pre-existing stresses (e.g. ∼ 2% normoxic/hypoxic interface for more accurate measurement of treatment response. The applied methodology provides an elegant, widely applicable approach to directly characterize spheroid (and other organoid cultures in biomedical and

  19. Caracterización de la capa de boruros formada durante la austenización de un hierro nodular austemperizado//Characterization of borides coating formed during austenitization of an austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Urbano Ordóñez‐Hernández

    2015-01-01

    Full Text Available En este trabajo se ha investigado el efecto de la austenitización y el borurado simultáneos, a 950 ºC, en la microestructura, la microdureza Vickers y el espesor de la capa borurada en medio líquido de un hierro nodular austemperizado no aleado. Se demostró que es posible obtener una capa de boruros de hierro muy bien estructurada con la microdureza Vickers suficientemente alta (1400 HVy con adecuado espesor de capa de 67 μm, sobre un sustrato de ausferrita típico de las fundiciones nodulares austemperizadas. Por medio de un ensayo pin on disc modificado, se comprobó la superior resistencia al desgaste abrasivo de la capa de boruros depositada durante la austenización del ADI, comparada con la máxima obtenida durante el austempering de éste sin aplicar el recubrimiento.Palabras claves: hierro nodular, borurado, austenización, austemperizado.______________________________________________________________________________AbstractThe effect of simultaneous austenitization and boriding at 950 ºC, on microstructure, Vickers hardness and boronized layer thickness of a non alloyed austempered ductile iron has been investigated. It was demonstrated that it is possible to obtain a well formed boronized layer with a Vicker hardness sufficiently high (1400 HV, and with an appropriated 67μm layer thickness, on a typical ausferrite ADI substrate. By using a modified pin on disc test, it was demonstrated the higher abrasion wear resistance of borides layer deposited during ADI austenitization process, compared with Vickers hardness of low temperature noncoated austempered ductile iron.Key words: ductile iron, boriding, austenitization, austempering.

  20. The fusion of tissue spheroids attached to pre-stretched electrospun polyurethane scaffolds

    Directory of Open Access Journals (Sweden)

    Vince Beachley

    2014-11-01

    Full Text Available Effective cell invasion into thick electrospun biomimetic scaffolds is an unsolved problem. One possible strategy to biofabricate tissue constructs of desirable thickness and material properties without the need for cell invasion is to use thin (<2 µm porous electrospun meshes and self-assembling (capable of tissue fusion tissue spheroids as building blocks. Pre-stretched electrospun meshes remained taut in cell culture and were able to support tissue spheroids with minimal deformation. We hypothesize that elastic electrospun scaffolds could be used as temporal support templates for rapid self-assembly of cell spheroids into higher order tissue structures, such as engineered vascular tissue. The aim of this study was to investigate how the attachment of tissue spheroids to pre-stretched polyurethane scaffolds may interfere with the tissue fusion process. Tissue spheroids attached, spread, and fused after being placed on pre-stretched polyurethane electrospun matrices and formed tissue constructs. Efforts to eliminate hole defects with fibrogenic tissue growth factor-β resulted in the increased synthesis of collagen and periostin and a dramatic reduction in hole size and number. In control experiments, tissue spheroids fuse on a non-adhesive hydrogel and form continuous tissue constructs without holes. Our data demonstrate that tissue spheroids attached to thin stretched elastic electrospun scaffolds have an interrupted tissue fusion process. The resulting tissue-engineered construct phenotype is a direct outcome of the delicate balance of the competing physical forces operating during the tissue fusion process at the interface of the pre-stretched elastic scaffold and the attached tissue spheroids. We have shown that with appropriate treatments, this process can be modulated, and thus, a thin pre-stretched elastic polyurethane electrospun scaffold could serve as a supporting template for rapid biofabrication of thick tissue

  1. β-Catenin-regulated ALDH1A1 is a target in ovarian cancer spheroids.

    Science.gov (United States)

    Condello, S; Morgan, C A; Nagdas, S; Cao, L; Turek, J; Hurley, T D; Matei, D

    2015-04-30

    Cancer cells form three-dimensional (3D) multicellular aggregates (or spheroids) under non-adherent culture conditions. In ovarian cancer (OC), spheroids serve as a vehicle for cancer cell dissemination in the peritoneal cavity, protecting cells from environmental stress-induced anoikis. To identify new targetable molecules in OC spheroids, we investigated gene expression profiles and networks upregulated in 3D vs traditional monolayer culture conditions. We identified ALDH1A1, a cancer stem cell marker as being overexpressed in OC spheroids and directly connected to key elements of the β-catenin pathway. β-Catenin function and ALDH1A1 expression were increased in OC spheroids vs monolayers and in successive spheroid generations, suggesting that 3D aggregates are enriched in cells with stem cell characteristics. β-Catenin knockdown decreased ALDH1A1 expression levels and β-catenin co-immunoprecipitated with the ALDH1A1 promoter, suggesting that ALDH1A1 is a direct β-catenin target. Both short interfering RNA-mediated β-catenin knockdown and A37 ((ethyl-2-((4-oxo-3-(3-(pryrrolidin-1-yl)propyl)-3,4-dihydrobenzo [4,5]thioeno [3,2-d]pyrimidin-2-yl)thio)acetate)), a novel ALDH1A1 small-molecule enzymatic inhibitor described here for the first time, disrupted OC spheroid formation and cell viability (Pmodel. These data strongly support the role of β-catenin-regulated ALDH1A1 in the maintenance of OC spheroids and propose new ALDH1A1 inhibitors targeting this cell population.

  2. Tumor-derived spheroids: Relevance to cancer stem cells and clinical applications.

    Science.gov (United States)

    Ishiguro, Tatsuya; Ohata, Hirokazu; Sato, Ai; Yamawaki, Kaoru; Enomoto, Takayuki; Okamoto, Koji

    2017-03-01

    Recently, many types of in vitro 3-D culture systems have been developed to recapitulate the in vivo growth conditions of cancer. The cancer 3-D culture methods aim to preserve the biological characteristics of original tumors better than conventional 2-D monolayer cultures, and include tumor-derived organoids, tumor-derived spheroids, organotypic multicellular spheroids, and multicellular tumor spheroids. The 3-D culture methods differ in terms of cancer cell sources, protocols for cell handling, and the required time intervals. Tumor-derived spheroids are unique because they are purposed for the enrichment of cancer stem cells (CSCs) or cells with stem cell-related characteristics. These spheroids are grown as floating spheres and have been used as surrogate systems to evaluate the CSC-related characteristics of solid tumors in vitro. Because eradication of CSCs is likely to be of clinical importance due to their association with the malignant nature of cancer cells, such as tumorigenicity or chemoresistance, the investigation of tumor-derived spheroids may provide invaluable clues to fight against cancer. Spheroid cultures have been established from cancers including glioma, breast, colon, ovary, and prostate cancers, and their biological and biochemical characteristics have been investigated by many research groups. In addition to the investigation of CSCs, tumor-derived spheroids may prove to be instrumental for a high-throughput screening platform or for the cultivation of CSC-related tumor cells found in the circulation or body fluids. © 2017 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.

  3. Radioresistance of human glioma spheroids and expression of HSP70, p53 and EGFr

    Directory of Open Access Journals (Sweden)

    Fedrigo Carlos A

    2011-11-01

    Full Text Available Abstract Background Radiation therapy is routinely prescribed for high-grade malignant gliomas. However, the efficacy of this therapeutic modality is often limited by the occurrence of radioresistance, reflected as a diminished susceptibility of the irradiated cells to undergo cell death. Thus, cells have evolved an elegant system in response to ionizing radiation induced DNA damage, where p53, Hsp70 and/or EGFr may play an important role in the process. In the present study, we investigated whether the content of p53, Hsp70 and EGFr are associated to glioblastoma (GBM cell radioresistance. Methods Spheroids from U-87MG and MO59J cell lines as well as spheroids derived from primary culture of tumor tissue of one GBM patient (UGBM1 were irradiated (5, 10 and 20 Gy, their relative radioresistance were established and the p53, Hsp70 and EGFr contents were immunohistochemically determined. Moreover, we investigated whether EGFr-phospho-Akt and EGFr-MEK-ERK pathways can induce GBM radioresistance using inhibitors of activation of ERK (PD098059 and Akt (wortmannin. Results At 5 Gy irradiation UGBM1 and U-87MG spheroids showed growth inhibition whereas the MO59J spheroid was relatively radioresistant. Overall, no significant changes in p53 and Hsp70 expression were found following 5 Gy irradiation treatment in all spheroids studied. The only difference observed in Hsp70 content was the periphery distribution in MO59J spheroids. However, 5 Gy treatment induced a significant increase on the EGFr levels in MO59J spheroids. Furthermore, treatment with inhibitors of activation of ERK (PD098059 and Akt (wortmannin leads to radiosensitization of MO59J spheroids. Conclusions These results indicate that the PI3K-Akt and MEK-ERK pathways triggered by EGFr confer GBM radioresistance.

  4. Scalable spheroid model of human hepatocytes for hepatitis C infection and replication.

    Science.gov (United States)

    Ananthanarayanan, Abhishek; Nugraha, Bramasta; Triyatni, Miriam; Hart, Stefan; Sankuratri, Suryanarayana; Yu, Hanry

    2014-07-07

    Developing effective new drugs against hepatitis C (HCV) virus has been challenging due to the lack of appropriate small animal and in vitro models recapitulating the entire life cycle of the virus. Current in vitro models fail to recapitulate the complexity of human liver physiology. Here we present a method to study HCV infection and replication on spheroid cultures of Huh 7.5 cells and primary human hepatocytes. Spheroid cultures are constructed using a galactosylated cellulosic sponge with homogeneous macroporosity, enabling the formation and maintenance of uniformly sized spheroids. This facilitates easy handling of the tissue-engineered constructs and overcomes limitations inherent of traditional spheroid cultures. Spheroids formed in the galactosylated cellulosic sponge show enhanced hepatic functions in Huh 7.5 cells and maintain liver-specific functions of primary human hepatocytes for 2 weeks in culture. Establishment of apical and basolateral polarity along with the expression and localization of all HCV specific entry proteins allow for a 9-fold increase in viral entry in spheroid cultures over conventional monolayer cultures. Huh 7.5 cells cultured in the galactosylated cellulosic sponge also support replication of the HCV clone, JFH (Japanese fulminant hepatitis)-1 at higher levels than in monolayer cultures. The advantages of our system in maintaining liver-specific functions and allowing HCV infection together with its ease of handling make it suitable for the study of HCV biology in basic research and pharmaceutical R&D.

  5. A microfluidic platform for chemoresistive testing of multicellular pleural cancer spheroids.

    Science.gov (United States)

    Ruppen, Janine; Cortes-Dericks, Lourdes; Marconi, Emanuele; Karoubi, Golnaz; Schmid, Ralph A; Peng, Renwang; Marti, Thomas M; Guenat, Olivier T

    2014-03-21

    This study reports on a microfluidic platform on which single multicellular spheroids from malignant pleural mesothelioma (MPM), an aggressive tumor with poor prognosis, can be loaded, trapped and tested for chemotherapeutic drug response. A new method to detect the spheroid viability cultured on the microfluidic chip as a function of the drug concentration is presented. This approach is based on the evaluation of the caspase activity in the supernatant sampled from the chip and tested using a microplate reader. This simple and time-saving method does only require a minimum amount of manipulations and was established for very low numbers of cells. This feature is particularly important in view of personalised medicine applications for which the number of cells obtained from the patients is low. MPM spheroids were continuously perfused for 48 hours with cisplatin, one of the standard chemotherapeutic drugs used to treat MPM. The 50% growth inhibitory concentration of cisplatin in perfused MPM spheroids was found to be twice as high as in spheroids cultured under static conditions. This chemoresistance increase might be due to the continuous support of nutrients and oxygen to the perfused spheroids.

  6. Catalytic Graphitization of Phenolic Resin

    Institute of Scientific and Technical Information of China (English)

    Mu Zhao; Huaihe Song

    2011-01-01

    The catalytic graphitization of thermal plastic phenolic-formaldehyde resin with the aid of ferric nitrate (FN) was studied in detail. The morphologies and structural features of the products including onion-like carbon nanoparticles and bamboo-shaped carbon nanotubes were investigated by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction and Raman spectroscopy measurements. It was found that with the changes of loading content of FN and residence time at 1000℃, the products exhibited various morphologies. The TEM images showed that bamboo-shaped carbon nanotube consisted of tens of bamboo sticks and onion-like carbon nanoparticle was made up of quasi-spherically concentrically closed carbon nanocages.

  7. Fracture mechanics of PGX graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ho, F.H.; Vollman, R.E.; Cull, A.D.

    1981-03-01

    Fracture mechanics tests were performed on grade PGX graphite. A compact tension specimen configuration which yields consistent values of the opening mode critical stress intensity factor K/sub IC/, was designed. For the calculation of the fracture toughness and crack growth rate the concept of the effective crack length is used. It corresponds to the crack length of a machined notched specimen with the same compliance. Fracture toughness testing was performed in two environments, air and helium, both at room temperature. The critical stress intensity factor, K/sub IC/, is calculated based on the maximum load and the effective crack length. The fatigue crack growth test was performed in air only. A break-in period was observed for the machined notch to develop into a naturally occurring crack path. Half of the fatigue life was spent in this period.

  8. Supermassive black holes and their host spheroids I. Galaxy vivisection

    CERN Document Server

    Savorgnan, Giulia A D

    2015-01-01

    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using $3.6 \\rm ~\\mu m$ $Spitzer$ imagery, which is a superb tracer of the stellar mass (superior to the $K$-band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and - for the first time - 2D kinematics, we were able to account for sph...

  9. Comptonization of cosmic microwave background photons in dwarf spheroidal galaxies

    Science.gov (United States)

    Culverhouse, Thomas L.; Evans, N. Wyn; Colafrancesco, S.

    2006-05-01

    We present theoretical modelling of the electron distribution produced by annihilating neutralino dark matter in dwarf spheroidal galaxies (dSphs). In particular, we follow up the idea of Colafrancesco and find that such electrons distort the cosmic microwave background (CMB) by the Sunyaev-Zeldovich (SZ) effect. For an assumed neutralino mass of 10 GeV and beam size of 1 arcsec, the SZ temperature decrement is of the order of nano-Kelvin for dSph models with a soft core. By contrast, it is of the order of micro-Kelvin for the strongly cusped dSph models favoured by some cosmological simulations. Although this is out of reach of current instruments, it may well be detectable by future mm telescopes, such as the Atacama Large Millimetre Array. We also show that the upscattered CMB photons have energies within reach of upcoming X-ray observatories, but that the flux of such photons is too small to be detectable now. None the less, we conclude that searching for the dark matter induced SZ effect is a promising way of constraining the dark distribution in dSphs, especially if the particles are light.

  10. Comptonisation of Cosmic Microwave Background Photons in Dwarf Spheroidal Galaxies

    CERN Document Server

    Culverhouse, T L; Colafrancesco, S; Culverhouse, Thomas L.

    2006-01-01

    We present theoretical modelling of the electron distribution produced by annihilating neutralino dark matter in dwarf spheroidal galaxies (dSphs). In particular, we follow up the idea of Colafrancesco (2004) and find that such electrons distort the cosmic microwave background (CMB) by the Sunyaev-Zeldovich effect. For an assumed neutralino mass of 10 GeV and beam size of 1'', the SZ temperature decrement is of the order of nano-Kelvin for dSph models with a soft core. By contrast, it is of the order of micro-Kelvin for the strongly cusped dSph models favoured by some cosmological simulations. Although this is out of reach of current instruments, it may well be detectable by future mm telescopes, such as ALMA. We also show that the upscattered CMB photons have energies within reach of upcoming X-ray observatories, but that the flux of such photons is too small to be detectable soon. Nonetheless, we conclude that searching for the dark matter induced Sunyaev-Zeldovich effect is a promising way of constraining ...

  11. Dwarf spheroidal galaxies as degenerate gas of free fermions

    CERN Document Server

    Domcke, Valerie

    2014-01-01

    In this paper we analyze a simple scenario in which Dark Matter (DM) consists of free fermions with mass $m_f$. We assume that on galactic scales these fermions are capable to form a degenerate Fermi gas, in which stability against gravitational collapse is ensured by the Pauli exclusion principle. The mass density of the resulting configuration is governed by a non-relativistic Lane-Emden equation, thus leading to a universal cored profile that depends only on one free parameter in addition to $m_f$. After reviewing the basic formalism, we test this scenario against experimental data describing the dispersion velocity of the eight classical dwarf spheroidal galaxies of the Milky Way. We find that, despite its extreme simplicity, the model exhibits a good fit of the data and realistic predictions for the size of DM halos providing that $m_f \\simeq 200$ eV. We propose a concrete realization of this model in which DM is produced non-thermally via inflaton decay. We show that imposing the correct relic abundance...

  12. Dwarf spheroidal galaxies as degenerate gas of free fermions

    Energy Technology Data Exchange (ETDEWEB)

    Domcke, Valerie; Urbano, Alfredo, E-mail: valerie.domcke@sissa.it, E-mail: alfredo.urbano@sissa.it [SISSA - International School for Advanced Studies, via Bonomea 256, Trieste, 34136 Italy (Italy)

    2015-01-01

    In this paper we analyze a simple scenario in which Dark Matter (DM) consists of free fermions with mass m{sub f}. We assume that on galactic scales these fermions are capable of forming a degenerate Fermi gas, in which stability against gravitational collapse is ensured by the Pauli exclusion principle. The mass density of the resulting con figuration is governed by a non-relativistic Lane-Emden equation, thus leading to a universal cored profile that depends only on one free parameter in addition to m{sub f}. After reviewing the basic formalism, we test this scenario against experimental data describing the velocity dispersion of the eight classical dwarf spheroidal galaxies of the Milky Way. We find that, despite its extreme simplicity, the model exhibits a good fit to the data and realistic predictions for the size of DM halos providing that m{sub f}≅ 200 eV. Furthermore, we show that in this setup larger galaxies correspond to the non-degenerate limit of the gas. We propose a concrete realization of this model in which DM is produced non-thermally via inflaton decay. We show that imposing the correct relic abundance and the bound on the free-streaming length constrains the inflation model in terms of inflaton mass, its branching ratio into DM and the reheating temperature.

  13. The effect of tides on the Fornax dwarf spheroidal galaxy

    CERN Document Server

    Battaglia, Giuseppina; Nipoti, Carlo

    2015-01-01

    Estimates of the mass distribution and dark-matter (DM) content of dwarf spheroidal galaxies (dSphs) are usually derived under the assumption that the effect of the tidal field of the host galaxy is negligible over the radial extent probed by kinematic data-sets. We assess the implications of this assumption in the specific case of the Fornax dSph by means of N-body simulations of a satellite orbiting around the Milky Way. We consider observationally-motivated orbits and we tailor the initial distributions of the satellite's stars and DM to match, at the end of the simulations, the observed structure and kinematics of Fornax. In all our simulations the present-day observable properties of Fornax are not significantly influenced by tidal effects. The DM component is altered by the interaction with the Galactic field (up to 20% of the DM mass within 1.6 kpc is lost), but the structure and kinematics of the stellar component are only mildly affected even in the more eccentric orbit (more than 99% of the stellar ...

  14. The structure of Andromeda II dwarf spheroidal galaxy

    CERN Document Server

    del Pino, Andrés; Hidalgo, Sebastian L; Fouquet, Sylvain

    2016-01-01

    We analyze in detail the spatial distribution and kinematic properties of two different stellar populations in Andromeda II (And II) dwarf spheroidal galaxy. We obtained their detailed surface density maps, together with their radial density profiles. The two populations differ not only in age and metallicity, but also in their spatial distribution and kinematics. Old stars ($\\gtrsim 11$ Gyr) follow a round distribution well fitted by truncated density profiles. These stars rotate around the projected optical major axis of the galaxy with line-of-sight velocities $v_{los}(r_h) = 16 \\pm 3$ km s$^{-1}$ and a velocity gradient of $2.06 \\pm 0.21$ km s$^{-1}$ arcmin$^{-1}$. Intermediate-age stars ($\\lesssim 9$ Gyr) concentrate in the centre of the galaxy and form an elongated structure extending along the projected optical major axis. This structure appears to rotate with a steeper velocity gradient, $2.24 \\pm 0.22$ km s$^{-1}$ arcmin$^{-1}$, and around the optical minor axis. The centres of rotation and kinetic p...

  15. The Evolution of Spheroidal Galaxies in Different Environments

    CERN Document Server

    Fritz, Alexander

    2009-01-01

    We analyse the kinematic and chemical evolution of 203 distant spheroidal (elliptical and S0) galaxies at 0.2

  16. Unbiased constraints on ultralight axion mass from dwarf spheroidal galaxies

    CERN Document Server

    Gonzáles-Morales, Alma X; Peñarrubia, Jorge; Ureña-López, Luis

    2016-01-01

    It has been suggested that the internal dynamics of dwarf spheroidal galaxies (dSphs) can be used to test whether or not ultralight axions with $m_a\\sim 10^{-22}\\text{eV}$ are a preferred dark matter candidate. However, comparisons to theoretical predictions tend to be inconclusive for the simple reason that while most cosmological models consider only dark matter, one observes only baryons. Here we use realistic kinematic mock data catalogs of Milky Way dSph's to show that the "mass-anisotropy degeneracy" in the Jeans equations leads to biased bounds on the axion mass in galaxies with unknown dark matter halo profiles. In galaxies with multiple chemodynamical components this bias can be partly removed by modelling the mass enclosed within each subpopulation. However, analysis of the mock data reveals that the least-biased constraints on the axion mass result from fitting the luminosity-averaged velocity dispersion of the individual chemodynamical components directly. Applying our analysis to two dSph's with ...

  17. Kinematic sub-populations in dwarf spheroidal galaxies

    CERN Document Server

    Ural, Ugur; Koch, Andreas; Gilmore, Gerard; Beers, Timothy C; Belokurov, Vasily; Evans, N Wyn; Grebel, Eva K; Vidrih, Simon; Zucker, Daniel B

    2008-01-01

    We present new spectroscopic data for twenty six stars in the recently-discovered Canes Venatici I (CVnI) dwarf spheroidal galaxy. We use these data to investigate the recent claim of the presence of two dynamically inconsistent stellar populations in this system (Ibata et al., 2006). We do not find evidence for kinematically distinct populations in our sample and we are able to obtain a mass estimate for CVnI that is consistent with all available data, including previously published data. We discuss possible differences between our sample and the earlier data set and study the general detectability of sub-populations in small kinematic samples. We conclude that in the absence of supporting observational evidence (for example, metallicity gradients), sub-populations in small kinematic samples (typically fewer than 100 stars) should be treated with extreme caution, as their detection depends on multiple parameters and rarely produces a signal at the 3sigma confidence level. It is therefore essential to determi...

  18. A Chemical Evolution Model for the Fornax Dwarf Spheroidal Galaxy

    CERN Document Server

    Yuan, Zhen; Jing, Y P

    2015-01-01

    Fornax is the brightest Milky Way (MW) dwarf spheroidal galaxy and its star formation history (SFH) has been derived from observations. We estimate the time evolution of its gas mass and net inflow and outflow rates from the SFH using a simple star formation law that relates the star formation rate to the gas mass. We present a chemical evolution model on a 2D mass grid with supernovae (SNe) as sources of metal enrichment. We find that a key parameter controlling the enrichment is the mass M_x of the gas to mix with the ejecta from each SN. The choice of M_x depends on the evolution of SN remnants and on the global gas dynamics. It differs between the two types of SNe involved and between the periods before and after Fornax became an MW satellite at time t = t_sat . Our results indicate that due to the global gas outflow at t > t_sat , part of the ejecta from each SN may directly escape from Fornax. Sample results from our model are presented and compared with data.

  19. The Dynamical and Chemical Evolution of Dwarf Spheroidal Galaxies

    CERN Document Server

    Revaz, Y; Sawala, T; Hill, V; Letarte, B; Irwin, M; Battaglia, G; Helmi, A; Shetrone, M D; Tolstoy, E; Venn, K A

    2009-01-01

    We present a large sample of fully self-consistent hydrodynamical Nbody/Tree-SPH simulations of isolated dwarf spheroidal galaxies (dSphs). It has enabled us to identify the key physical parameters and mechanisms at the origin of the observed variety in the Local Group dSph properties. The initial total mass (gas + dark matter) of these galaxies is the main driver of their evolution. Star formation (SF) occurs in series of short bursts. In massive systems, the very short intervals between the SF peaks mimic a continuous star formation rate, while less massive systems exhibit well separated SF bursts, as identified observationally. The delay between the SF events is controlled by the gas cooling time dependence on galaxy mass. The observed global scaling relations, luminosity-mass and luminosity-metallicity, are reproduced with low scatter. We take advantage of the unprecedentedly large sample size and data homogeneity of the ESO Large Programme DART, and add to it a few independent studies, to constrain the s...

  20. Conventional flow curves of liquid cast iron put on spheroidization

    Directory of Open Access Journals (Sweden)

    B. Borowiecki

    2008-04-01

    Full Text Available The purpose of the investigation was to confirm the hypothesis that the conventional flow curves of liquid cast iron put on sferoidization determined from the rod fluidity test are comparable to flow curves of liquids in environmental temperature. Moreover has been identified, that conventional flow curves for this liquid cast iron are similar to generalized non- Newtonian liquids curves.For rods with the diameters 3-8 mm there are three various curves:1 – the flow curve of liquid cast iron put on spheroidization overheated about 80 K resemble a shape adequately to a curve of densified liquid with shearing. This phenomenon can be caused by high overcooled and creation of crystallization nuclei;2 – metal alloys overheated about 180 K resemble a shape adequately to Newtonian liquid;3 – metal alloys overheated about 210 K resemble a shape of curve adequately to dispersed liquid with shearing. This phenomenon probably depends on influence of gas which creates on boundary of metal-sand mould.