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Sample records for nonmetallic inclusions creep

  1. Non-metallic inclusions in high manganese austenitic alloys

    OpenAIRE

    A. Grajcar; L. Bulkowski; U. Galisz

    2011-01-01

    Purpose: The aim of the paper is to identify the type, fraction and chemical composition of non-metallic inclusions modified by rare-earth elements in an advanced group of high-manganese austenitic C-Mn-Si-Al-type steels with Nb and Ti microadditions.Design/methodology/approach: The heats of 3 high-Mn steels of a various content of Si, Al and Ti were melted in a vacuum induction furnace and a modification of non-metallic inclusions was carried out by the mischmetal in the amount of 0.87 g or ...

  2. Non-metallic Inclusions in Continuously Cast Aluminum Killed Steels

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In aluminum killed steels, the size, shape, quantity and formation of non-metallic inclusions in ladle steel (before and after RH vacuum treatment) and in tundish as well as in slabs were studied by EPMA (Electron Probe Microanalysis) and by analyzing the total oxygen. The results showed that in the slabs the total oxygen was quite low and the inclusions discovered were mainly small-sized angular alumina inclusions. This indicates that most inclusions have been removed by floating out during the continuous casting process. In addition, the countermeasures were discussed to decrease the alumina inclusions in the slabs further.

  3. The Measurement of Hardness and Elastic Modulus of non-Metallic Inclusions in Steely Welding Joints

    Directory of Open Access Journals (Sweden)

    Ignatova Anna

    2015-08-01

    Full Text Available Trunk pipelines work under a cyclic dynamical mechanical load because when oil or gas is pumped, the pressure constantly changes - pulsates. Therefore, the fatigue phenomenon is a common reason of accidents. The fatigue phenomenon more often happens in the zone of non-metallic inclusions concentration. To know how the characteristics of nonmetallic inclusions influence the probability of an accident the most modern research methods should be used. It is determined with the help of the modern research methods that the accident rate of welded joints of pipelines is mostly influenced by their morphological type, composition and size of nonmetallic inclusions, this effect is more important than the common level of pollution by non-metallic inclusions. The article presents the results of the investigations of welded joints, obtained after the use of different common welding materials. We used the methods, described in the state standards: scanning electronic microscopy, spectral microprobe analysis and nano-indentation. We found out that non-metallic inclusions act like stress concentrators because they shrink, forming a blank space between metal and nonmetallic inclusions; it strengthens the differential properties on this boundary. Nonmetallic inclusion is not fixed, it can move. The data that we have received mean that during welded joints’ contamination (with non-metallic inclusions monitoring process, more attention should be paid to the content of definite inclusions, but not to total contamination.

  4. The Effect of Different Non-Metallic Inclusions on the Machinability of Steel

    OpenAIRE

    Niclas Ånmark; Andrey Karasev; Pär Göran Jönsson

    2015-01-01

    Considerable research has been conducted over recent decades on the role of non-metallic inclusions and their link to the machinability of different steels. The present work reviews the mechanisms of steel fractures during different mechanical machining operations and the behavior of various non-metallic inclusions in a cutting zone. More specifically, the effects of composition, size, number and morphology of inclusions on machinability factors (such as cutting tool wear, power consumption, ...

  5. Effect of the conditions of REM microalloying of steel on the corrosion activity of nonmetallic inclusions

    Science.gov (United States)

    Movenko, D. A.; Kotel'nikov, G. I.; Pavlov, A. V.; Bytsenko, O. A.

    2015-11-01

    Experimental heats of low-alloy steel are performed under various conditions of rare-earth metal microalloying and aluminum and calcium deoxidation. Electron-probe microanalysis of nonmetallic inclusions and a metallographic investigation of a metal are used to show that, when interacting with water, nonmetallic cerium oxide inclusions do not form hydrates and, correspondingly, are not aggressive. When aluminum, calcium, and cerium additions are sequentially introduced into a melt, a continuous cerium oxide shell forms on calcium aluminates, protects corrosive nonmetallic inclusions against interaction with water, and weakens local metal corrosion.

  6. Size of Non-Metallic Inclusions in High-Grade Medium Carbon Steel

    OpenAIRE

    Lipiński T.; Wach A.

    2014-01-01

    Non-metallic inclusions found in steel can affect its performance characteristics. Their impact depends not only on their quality, but also, among others, on their size and distribution in the steel volume. The literature mainly describes the results of tests on hard steels, particularly bearing steels. The amount of non-metallic inclusions found in steel with a medium carbon content melted under industrial conditions is rarely presented in the literature. The tested steel was melted in an el...

  7. Fatigue Strength Prediction of Drilling Materials Based on the Maximum Non-metallic Inclusion Size

    Science.gov (United States)

    Zeng, Dezhi; Tian, Gang; Liu, Fei; Shi, Taihe; Zhang, Zhi; Hu, Junying; Liu, Wanying; Ouyang, Zhiying

    2015-12-01

    In this paper, the statistics of the size distribution of non-metallic inclusions in five drilling materials were performed. Based on the maximum non-metallic inclusion size, the fatigue strength of the drilling material was predicted. The sizes of non-metallic inclusions in drilling materials were observed to follow the inclusion size distribution rule. Then the maximum inclusion size in the fatigue specimens was deduced. According to the prediction equation of the maximum inclusion size and fatigue strength proposed by Murakami, fatigue strength of drilling materials was obtained. Moreover, fatigue strength was also measured through rotating bending tests. The predicted fatigue strength was significantly lower than the measured one. Therefore, according to the comparison results, the coefficients in the prediction equation were revised. The revised equation allowed the satisfactory prediction results of fatigue strength of drilling materials at the fatigue life of 107 rotations and could be used in the fast prediction of fatigue strength of drilling materials.

  8. The Effect of Different Non-Metallic Inclusions on the Machinability of Steels.

    Science.gov (United States)

    Ånmark, Niclas; Karasev, Andrey; Jönsson, Pär Göran

    2015-02-16

    Considerable research has been conducted over recent decades on the role of non‑metallic inclusions and their link to the machinability of different steels. The present work reviews the mechanisms of steel fractures during different mechanical machining operations and the behavior of various non-metallic inclusions in a cutting zone. More specifically, the effects of composition, size, number and morphology of inclusions on machinability factors (such as cutting tool wear, power consumption, etc.) are discussed and summarized. Finally, some methods for modification of non-metallic inclusions in the liquid steel are considered to obtain a desired balance between mechanical properties and machinability of various steel grades.

  9. The Effect of Different Non-Metallic Inclusions on the Machinability of Steels

    Directory of Open Access Journals (Sweden)

    Niclas Ånmark

    2015-02-01

    Full Text Available Considerable research has been conducted over recent decades on the role of non‑metallic inclusions and their link to the machinability of different steels. The present work reviews the mechanisms of steel fractures during different mechanical machining operations and the behavior of various non-metallic inclusions in a cutting zone. More specifically, the effects of composition, size, number and morphology of inclusions on machinability factors (such as cutting tool wear, power consumption, etc. are discussed and summarized. Finally, some methods for modification of non-metallic inclusions in the liquid steel are considered to obtain a desired balance between mechanical properties and machinability of various steel grades.

  10. Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels

    Directory of Open Access Journals (Sweden)

    M. Opiela

    2012-04-01

    Full Text Available The modification of the chemical composition of non-metallic inclusions by rare-earth elements in the new-developed microalloyed steels was discussed in the paper. The investigated steels are assigned to production of forged elements by thermo- mechanical treatment. The steels were melted in a vaccum induction furnace and modification of non-metallic inclusions was carried out by the michmetal in the amount of 2.0 g per 1 kg of steel. It was found that using material charge of high purity and a realization of metallurgical process in vacuous conditions result in a low concentration of sulfur (0.004%, phosphorus (from 0.006 to 0.008% and oxygen (6 ppm. The high metallurgical purity is confirmed by a small fraction of non-metallic inclusions averaging 0.075%. A large majority of non-metallic inclusions are fine, globular oxide-sulfide or sulfide particles with a mean size 17m2. The chemical composition and morphology of non-metallic inclusions was modified by Ce, La and Nd, what results a small deformability of non- metallic inclusions during hot-working.

  11. Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels

    OpenAIRE

    Opiela M.; Grajcar A.

    2012-01-01

    The modification of the chemical composition of non-metallic inclusions by rare-earth elements in the new-developed microalloyed steels was discussed in the paper. The investigated steels are assigned to production of forged elements by thermo- mechanical treatment. The steels were melted in a vaccum induction furnace and modification of non-metallic inclusions was carried out by the michmetal in the amount of 2.0 g per 1 kg of steel. It was found that using material charge of high purity and...

  12. Size of Non-Metallic Inclusions in High-Grade Medium Carbon Steel

    Directory of Open Access Journals (Sweden)

    Lipiński T.

    2014-12-01

    Full Text Available Non-metallic inclusions found in steel can affect its performance characteristics. Their impact depends not only on their quality, but also, among others, on their size and distribution in the steel volume. The literature mainly describes the results of tests on hard steels, particularly bearing steels. The amount of non-metallic inclusions found in steel with a medium carbon content melted under industrial conditions is rarely presented in the literature. The tested steel was melted in an electric arc furnace and then desulfurized and argonrefined. Seven typical industrial melts were analyzed, in which ca. 75% secondary raw materials were used. The amount of non-metallic inclusions was determined by optical and extraction methods. The test results are presented using stereometric indices. Inclusions are characterized by measuring ranges. The chemical composition of steel and contents of inclusions in every melts are presented. The results are shown in graphical form. The presented analysis of the tests results on the amount and size of non-metallic inclusions can be used to assess them operational strength and durability of steel melted and refined in the desulfurization and argon refining processes.

  13. Behavior of Non-metallic Inclusions in Centrifugal Induction Electroslag Castings

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    (para)In order to know the behavior of non-metallic inclusions in centrifugal induction electroslag castings (CIESC), non-metallic inclusions in 5CrMnMo and 4Cr5MoSiV1 were qualitatively and quantitatively analyzed. The largest size of inclusions in the casting and the thermodynamic possibility of TiN precipitation in steel were also calculated. The results show that sulfide inclusions are evenly distributed and the content is low. The amount of oxide inclusions in CIESC 4Cr5MoSiV1 steel is close to the ESR steel and lower than that in the EAF steel, and there are some differences along radial direction. Nitride inclusions are fine and the diameter of the largest one is 3~4um. With the increase of the centrifugal machine's rotational speed, the ratio of round inclusions increases and the ratio of sharp inclusions decreases. According to the experiment and the calculation results, it is pointed out that the largest diameter of non-metallic inclusions in the CIESC 4Cr5MoSiV1 casting is only 6.6mu, and [N%][Ti%] in 4Cr5MoSiV1 steel should be controlled less than 4.4~#U00d7tex010^{-5} in order to further reduce the amount and size of TiN inclusions.

  14. Evaluation of Characteristics of Non-Metallic Inclusions in P/M Ni-Base Superalloy by Automatic Image Analysis

    Institute of Scientific and Technical Information of China (English)

    Li; Xinggang; Ge; Changchun; Shen; Weiping

    2007-01-01

    Non-metallic inclusions,especially the large ones,within P/M Ni-base superalloy have a major influence on fatigue characteristics,but are not directly measurable by routine inspection.In this paper,a method,automatic image analysis,is proposed for estimation of the content,size and amount of non-metallic inclusions in superalloy.The methodology for the practical application of this method is described and the factors affecting the precision of the estimation are discussed.In the experiment,the characteristics of the non-metallic inclusions in Ni-base P/M superalloy are analyzed.

  15. Nonmetallic Inclusion Control of 350 km/h High Speed Rail Steel

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ke-wen; ZENG Jian-hua; WANG Xin-hua

    2009-01-01

    Inclusion has an important effect on quality of high speed rail steel.In consideration of the lower acceptance percentage of the inclusion and its constraint against the requirement for large scale production of 350 km/h high speed rail steel in Panzhihua Iron and Steel (Group) Co,the technology of nonmetallic inclusion control for 350 km/h high speed rail steel was studied.An optimized model of the argon-blowing in ladle furnace (LF),the control of the components of the ladle slag,and the technique of calcium treatment for the molten steel was brought forward.Using the researched technology,the removal ratio of the inclusion was increased and the components,distribution,and shape of the inclusion in the rail steel were changed,which resulted in a reduction in the average total oxygen content to 10.17×10-6 and an increase in the comprehensive acceptance percentage of the nonmetallic inclusion from 48.21% to 98.1%.Test has shown that this metallurgical technology can meet the requirement for large scale production of 350 km/h high speed steel in Panzhihua Iron and Steel (Group) Co.

  16. Complex Nonmetallic Inclusions Formed in Billets Heated for Rolling and Characteristics of Structural Steels

    Science.gov (United States)

    Zaitsev, A. I.; Koldaev, A. V.; Arutyunyan, N. A.; Shaposhnikov, N. G.; Dunaev, S. F.

    2017-03-01

    Complex bimetallic inclusions formed in billets from steels 09G2S and K52 during heating for rolling are studied by methods of electron microscopy and local x-ray spectrum analysis. To check the established evolution of oxide inclusions based on aluminomagnesium spinel and other oxide compositions, individual inclusions of manganese sulfide and complex oxide-sulfide inclusions, a method developed by the Severstal'Company and the Karpov NIFKhI for determining the content of corrosion-active nonmetallic inclusions (CANI) as a function of the heating mode is applied to the steels studied. It is recommended to increase the temperature and duration of heating of billets for hot rolling in order to lower the content of CANI and to raise the resistance of the steels to local corrosion.

  17. 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.

  18. Quantitative Study on Nonmetallic Inclusion Particles in Steels by Automatic Image Analysis With Extreme Values Method

    Institute of Scientific and Technical Information of China (English)

    Cássio Barbosa; José Brant de Campos; J(ǒ)neo Lopes do Nascimento; Iêda Maria Vieira Caminha

    2009-01-01

    The presence of nonmetallic inclusion particles which appear during steelmaking process is harmful to the properties of steels, which is mainly as a function of some aspects such as size, volume fraction, shape, and distribution of these particles. The automatic image analysis technique is one of the most important tools for the quantitative determination of these parameters. The classical Student approach and the Extreme Values Method (EVM) were used for the inclusion size and shape determination and the evaluation of distance between the inclusion particles. The results thus obtained indicated that there were significant differences in the characteristics of the inclusion particles in the analyzed products. Both methods achieved results with some differences, indicating that EVM could be used as a faster and more reliable statistical methodology.

  19. Morphology and Orientation Selection of Non-metallic Inclusions in Electrified Molten Metal

    Science.gov (United States)

    Zhao, Z. C.; Qin, R. S.

    2017-10-01

    The effect of electric current on morphology and orientation selection of non-metallic inclusions in molten metal has been investigated using theoretical modeling and numerical calculation. Two geometric factors, namely the circularity ( fc ) and alignment ratio ( fe ) were introduced to describe the inclusions shape and configuration. Electric current free energy was calculated and the values were used to determine the thermodynamic preference between different microstructures. Electric current promotes the development of inclusion along the current direction by either expatiating directional growth or enhancing directional agglomeration. Reconfiguration of the inclusions to reduce the system electric resistance drives the phenomena. The morphology and orientation selection follow the routine to reduce electric free energy. The numerical results are in agreement with our experimental observations.

  20. Magnetohydrodynamic study of electromagnetic separation of nonmetallic inclusions from aluminum melt

    Institute of Scientific and Technical Information of China (English)

    SHU; Da(疏达); SUN; Baode(孙宝德); WANG; Jun(王俊); ZHANG; Xueping(张雪萍); ZHOU; Yaohe(周尧和)

    2002-01-01

    Magnetohydrodynamic flow around the nonmetallic inclusions in aluminum melt and the force exerted on the inclusions were explored by dimensional analysis and numerical calculations. Dimensional analysis shows that the invariant characterizes the force exerted on the inclusions and the flow intensity of the melt. The physical significance of A is represented as a modified particle Reynolds number that reflects the effects of electromagnetic force. The fluid flow around the particle becomes unstable when A>2×103. It is shown that the neglect of the inertial terms has little effect on the force exerted on the inclusions in the range of A≤1×106. However, the analytical solution of the maximum velocity inside the melt does not apply due to the appearance of turbulent flow in the case of A>2×103.

  1. Influence of non-metallic inclusions on the strength properties of screws made of 35B2+Cr steel after softening

    OpenAIRE

    Krawczyk, J.; Pawłowski, B

    2012-01-01

    Purpose: This paper presents the results of the research on the influence of non-metallic inclusions on strength properties of 35B2+Cr steel screws.Design/methodology/approach: The investigations were carried out on screws after softening. The investigated steels with different fraction of non-metallic inclusions were delivered by three different suppliers.Findings: It was proved, that in spite of the level of fraction of non-metallic inclusions compatible with the corresponding standards, th...

  2. Non-metallic inclusions structure dimension in high quality steel with medium carbon contents

    Directory of Open Access Journals (Sweden)

    T. Lipiński

    2009-07-01

    Full Text Available The experimental material consisted of semi-finished products of high-grade, medium-carbon structural steel. The production process involved two melting technologies: steel melting in a 140-ton basic arc furnace with desulfurization and argon refining variants, and in a 100-ton oxygen converter. Billet samples were collected to analyze the content of non-metallic inclusions with the use of an optical microscope and a video inspection microscope. The results were processed and presented in graphic form.

  3. The Effect of Fine Non-Metallic Inclusions on the Fatigue Strength of Structural Steel

    Directory of Open Access Journals (Sweden)

    Lipiński T.

    2015-04-01

    Full Text Available The article discusses the results of a study investigating the effect of the number of fine non-metallic inclusions (up to 2 µm in size on the fatigue strength of structural steel during rotary bending. The study was performed on 21 heats produced in an industrial plant. Fourteen heats were produced in 140 ton electric furnaces, and 7 heats were performed in a 100 ton oxygen converter. All heats were desulfurized. Seven heats from electrical furnaces were refined with argon, and heats from the converter were subjected to vacuum circulation degassing.

  4. Absorption of non-metallic inclusions by steelmaking slags—a review

    Directory of Open Access Journals (Sweden)

    Bruno Henrique Reis

    2014-04-01

    Full Text Available The formation of non-metallic inclusions during steelmaking is inevitable and, when not properly controlled, can cause performance and production problems. Slag is one of the resources available to carry out this control. In steelmaking, it is generally understood that inclusions are naturally absorbed by slag when flotation is sufficient. However, separation and dissolution may define the inclusion absorption capacity of slag. The discussion in this review explains the relationship between separation and the contact angle at the steel/inclusion interface, which differentiates the mechanism from liquid and solid inclusions. Whereas liquid particles show more predictable behavior in experimental observations, thermodynamic analysis is necessary in order to describe the removal of solid particles. Among other findings, it is evident that slag viscosity and the formation of compounds at the inclusion/slag interface strongly influence inclusion dissolution capacity. Following a detailed description of findings in the literature, this review considers the most influential factors to aid in optimizing slags for inclusion absorption.

  5. Detection of Non-metallic Inclusions in Centrifugal Continuous Casting Steel Billets

    Science.gov (United States)

    Wang, Qiangqiang; Zhang, Lifeng; Seetharaman, Sridhar; Yang, Shufeng; Yang, Wen; Wang, Yi

    2016-06-01

    In the current study, automated particle analysis was employed to detect non-metallic inclusions in steel during a centrifugal continuous casting process of a high-strength low alloy steel. The morphology, composition, size, area fraction, amount, and spatial distribution of inclusions in steel were obtained. Etching experiment was performed to reveal the dendrite structure of the billet and to discuss the effect of centrifugal force on the distribution of oxide inclusions in the final solidified steel by comparing the solidification velocity with the critical velocity reported in literature. It was found that the amount of inclusions was highest in samples from the tundish (~250 per mm2), followed by samples from the mold (~200 per mm2), and lowest in billet samples (~86 per mm2). In all samples, over 90 pct of the inclusions were smaller than 2μm. In steel billets, the content of oxides, dual-phase oxide-sulfides, and sulfides in inclusions were found to be 10, 30, and 60 pct, respectively. The dual-phase inclusions were oxides with sulfides precipitated on the outer surface. Oxide inclusions consisted of high Al2O3 and high MnO which were solid at the molten steel temperature, implying that the calcium treatment was insufficient. Small oxide inclusions very uniformly distributed on the cross section of the billet, while there were more sulfide inclusions showing a banded structure at the outside 25 mm layer of the billet. The calculated solidification velocity was higher than the upper limit at which inclusions were entrapped by the solidifying front, revealing that for oxide inclusions smaller than 8μm in this study, the centrifugal force had little influence on its final distribution in billets. Instead, oxide inclusions were rapidly entrapped by solidifying front.

  6. Standard practice for extreme value analysis of nonmetallic inclusions in steel and other microstructural features

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This practice describes a methodology to statistically characterize the distribution of the largest indigenous nonmetallic inclusions in steel specimens based upon quantitative metallographic measurements. The practice is not suitable for assessing exogenous inclusions. 1.2 Based upon the statistical analysis, the nonmetallic content of different lots of steels can be compared. 1.3 This practice deals only with the recommended test methods and nothing in it should be construed as defining or establishing limits of acceptability. 1.4 The measured values are stated in SI units. For measurements obtained from light microscopy, linear feature parameters shall be reported as micrometers, and feature areas shall be reported as micrometers. 1.5 The methodology can be extended to other materials and to other microstructural features. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish app...

  7. The share of non-metallic inclusions in high-grade steel for machine parts

    Directory of Open Access Journals (Sweden)

    T. Lipiński

    2010-10-01

    Full Text Available The aim of this work was to compare the differences in the purity steel in the dimensions of inclusion particles as dependent on various steel production processes. The experimental material consisted of semi-finished products of high-grade, medium-carbon constructional steel with: manganese, chromium, nickel, molybdenum and boron. The impurity content of steel was low as phosphorus and sulphur levels did not exceed 0.025%. The experimental material consisted of steel products obtained in three metallurgical processes: electric, electric with argon refining and oxygen converter with vacuum degassing of steel. Billet samples were collected to determine: chemical composition, relative volume of non-metallic inclusions, dimensions of impurities. The results were processed and presented in graphic form.

  8. Effectiveness of Shot Peening In Suppressing Fatigue Cracking At Non-Metallic Inclusions In Udimet(Registered Trademark)720

    Science.gov (United States)

    Barrie, Robert L.; Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Prescenzi, Anthony; Biles, T.; Bonacuse, P. J.

    2006-01-01

    The fatigue lives of modern powder metallurgy disk alloys can be reduced over an order of magnitude by cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet 720. Multiple strain-controlled fatigue tests were then performed on machined specimens with and without shot peened test sections at 427 C and 650 C. The low cycle fatigue lives and failure initiation sites varied as functions of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with the introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. These inclusions reduced fatigue life by up to 100X, when compared to lives of material without inclusions residing at specimen surface. Large inclusions produced the greatest reductions in life for tests at low strain ranges and high strain ratios. Shot peening improved life in many cases by reducing the most severe effects of inclusions.

  9. Effectiveness of Shot Peening in Suppressing Fatigue Cracking at Non-Metallic Inclusions in Udimet(trademark) 720

    Science.gov (United States)

    Barrie, Robert L.; Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Prescenzi, Anthony; Biles, Tiffany; Bonacuse, Peter J.

    2005-01-01

    The fatigue lives of modern powder metallurgy disk alloys can be reduced by over an order of magnitude by surface cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet 720. Multiple strain-controlled fatigue tests were then performed on machined specimens at 427 and 650 C in peened and unpeened conditions. Analyses were performed to compare the low cycle fatigue lives and failure initiation sites as a function of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. The inclusions could reduce fatigue life by up to 100X. Large inclusions had the greatest effect on life in tests at low strain ranges and high strain ratios. Shot peening can be used to improve life in these conditions by reducing the most severe effects of inclusions.

  10. Effect of Non-metallic Inclusions in Fe-Al-Ti-O-N-S Alloy on Grain Size

    Science.gov (United States)

    Choi, Wonjin; Matsuura, Hiroyuki; Tsukihashi, Fumitaka

    2016-06-01

    The effect of characteristics of non-metallic inclusions in Fe-Al-Ti-O-N-S alloys with various compositions at 1473 K (1200 °C) on the microstructure was studied. The ASTM grain size number was determined in as-cast and heated samples by the optical microscopy, and the inclusion types in each sample were determined from composition analysis by field-emission scanning electron microscope with energy-dispersive spectroscopy. The TiN-based inclusions certainly had a positive effect on the grain refinement. On the other hand, TiS-based inclusions exhibited no influence on the decrease of grain size. In addition, the formation and evolution behavior of inclusions by heating solid-state Fe-Al-Ti-O-N-S alloys with those locations were clarified. A different change of inclusions in alloys was observed depending on the distribution and composition of inclusions.

  11. Numerical analysis of the non-metallic inclusions distribution and separation in a two-strand tundish

    Directory of Open Access Journals (Sweden)

    T. Merder

    2013-04-01

    Full Text Available The tundish plays an important role in the challenging task of a “clean steel” production process. The flow of the liquid steel in tundish has a crucial influence on non-metallic inclusions distribution and separation. The article presents computational studies of non-metallic inclusions separation in a two-strand industrial tundish during steady-state casting. Tundish capacity is 7,5 t. First, flow structure in the tundish was investigated using water model of the industrial tundish in a 1:2 scale. The experimental results, regarding RTD characteristics were used to validate numerical model. With validated model, particle distribution and separation in the two-strand tundish were investigated numerically. For modelling the separation of particles at the fluid surface, a modified boundary condition has been implemented.

  12. Effects of Zr, Ti, and Al Additions on Nonmetallic Inclusions and Impact Toughness of Cast Low-Alloy Steel

    Science.gov (United States)

    Bizyukov, Pavel V.; Giese, Scott R.

    2017-03-01

    A microalloying of the low-carbon and low-alloy cast steel was conducted with Zr, Ti, and Al that were added to the steel in four combinations. After heat treatment, the samples were tested for impact toughness at room temperature using the Charpy method. The highest values of impact toughness were obtained in the group treated with Zr, while Zr-Ti and Zr-Ti-Al groups showed moderate toughness values; the lowest values were observed in the Zr-Al group. Difference among the treatment groups was observed in the fracture mechanisms, morphology, and area distribution of the inclusions. High toughness values achieved in the trials treated with zirconium corresponded with smooth ductile fracture. The metal treated with a combination of zirconium and titanium had a relatively small area occupied by inclusions, but its toughness was also moderate. Lowest impact toughness values corresponded with the larger area occupied by the inclusions in the trials treated with aluminum. Also, a connection between the solubility product [Al][N] and impact toughness was established. The study also provides a qualitative description and quantitative analysis of the nonmetallic inclusions formation as a result of microalloying treatment. The precipitation sequence of the inclusions was described based on the thermochemical calculations for the nonmetallic compounds discovered in the experimental steel. A description of the size distribution, morphology, and composition was conducted for the oxides, nitrides, sulfides, and multiphase particles.

  13. AES and SIMS analysis of non-metallic inclusions in a low-carbon chromium-steel.

    Science.gov (United States)

    Gammer, Katharina; Rosner, M; Poeckl, G; Hutter, H

    2003-05-01

    In the final step of secondary metallurgical steel processing, calcium is added. Besides Mg, Ca is the most powerful deoxidiser and desulfurisation agent. It reacts with dissolved oxygen and sulfur and reduces oxides and sulfides thereby forming non-metallic inclusions. Within this paper we present the analysis of such inclusions in a low-carbon chromium-steel. Depending on the time of quenching of the steel sample, different structures were revealed by REM, Auger and SIMS: If the steel was quenched immediately after Ca-addition, non-metallic inclusions that appeared to have "cavities" could be detected with SEM. SIMS investigations of these particles showed ring-shaped structures and revealed that the ring is made up of Al, Ca, Mg, O and S. No secondary ions however could be retrieved from the core inside the ring, thus leaving the nature of the "cavities" unclear. If the steel sample was quenched 3 min after Ca addition, inclusions did not have a ring-shaped structure but a compact one.

  14. Effect of Acid-Soluble Aluminum on the Evolution of Non-metallic Inclusions in Spring Steel

    Science.gov (United States)

    Wang, Yong; Tang, Haiyan; Wu, Tuo; Wu, Guanghui; Li, Jingshe

    2017-04-01

    The content of acidic soluble aluminum in molten steel ([Al]s) is of significance to the control of total oxygen (TO), the formation of non-metallic inclusions, and the improvement of the surface quality of billets. Industrial trials and thermodynamic calculations were performed to study the effects of [Al]s content on the TO and the evolution of non-metallic inclusions in 60Si2Mn-Cr spring steel that was deoxidized by Si-Mn ((low aluminum process (LAP)) and Si-Mn-Al (high aluminum process (HAP)). The results show that the [Al]s contents in billets are within 0.0060 to 0.0069 mass pct in the LAP and 0.016 to 0.055 mass pct in the HAP. The TO content at each station of the LAP is higher than that in the HAP; the inclusions of billets were mainly of the CaO-Al2O3-SiO2 type in the former, and of the CaO-Al2O3-MgO and CaS-Al2O3-MgO types in the latter. A tendency is found that the higher the [Al]s, the easier it is to deviate from the low melting point region of the inclusion distribution and the larger the size of the inclusions. The relationships between [Al]s and the melting point of the oxide inclusions and the Al2O3 content in the oxide inclusions are also discussed in terms of experiment and calculation.

  15. Influence of Low-Alloy Cast Steel Modification on Primary Structure Refinement, Type and Shape of Non-Metallic Inclusions

    Directory of Open Access Journals (Sweden)

    Bartocha D.

    2015-04-01

    Full Text Available In the article there are presented methods and results of investigation which main aim were determination of influence of melting technology (gas extraction, vacuum refining, slag refining and extraction, deoxidation and degassing and type of used modifiers on the type and shape of non-metallic inclusions and the primary structure refining. Low alloy cast steel melted in laboratory conditions, in an inductive furnace was investigated. Additions of FeNb, FeV, FeTi and FeZr modifiers were applied. The contents of oxygen and nitrogen in obtained cast steel were determined.

  16. Study on Non-Metallic Inclusions in Laser-Welded TRIP-Aided Nb-Microalloyed Steel

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    Grajcar A.

    2014-10-01

    Full Text Available The work concerns the studies on non-metallic inclusions occuring in laser-welded Si-Al TRIP steel containing Nb and Ti microadditions. Laser welding tests of 2 mm thick thermomechanically rolled sheets were carried out using keyhole welding and a solid-state laser. The results of laser welding in the air atmosphere for the heat input value of 0.048 kJ/mm are included. The distribution, type and chemical composition of non-metallic inclusions formed in the base metal, heat-affected zone, and fusion zone are analysed in detail. It was found that the base metal contains rare, fine oxysulphides. Their chemical composition was modified by rare earth elements. Numerous oxide inclusions of a various size and a chemical composition occur in the fusion zone. The dependence between a size of particles and their chemical composition was observed. A microstructure of steel was assessed using light microscopy and scanning electron microscopy techniques.

  17. Non-Metallic Inclusions and Hot-Working Behaviour of Advanced High-Strength Medium-Mn Steels

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    Grajcar A.

    2016-06-01

    Full Text Available The work addresses the production of medium-Mn steels with an increased Al content. The special attention is focused on the identification of non-metallic inclusions and their modification using rare earth elements. The conditions of the thermomechanical treatment using the metallurgical Gleeble simulator and the semi-industrial hot rolling line were designed for steels containing 3 and 5% Mn. Hot-working conditions and controlled cooling strategies with the isothermal holding of steel at 400°C were selected. The effect of Mn content on the hot-working behaviour and microstructure of steel was addressed. The force-energetic parameters of hot rolling were determined. The identification of structural constituents was performed using light microscopy and scanning electron microscopy methods. The addition of rare earth elements led to the total modification of non-metallic inclusions, i.e., they replaced Mn and Al forming complex oxysulphides. The Mn content in a range between 3 and 5% does not affect the inclusion type and the hot-working behaviour. In contrast, it was found that Mn has a significant effect on a microstructure.

  18. Characteristics and Modification of Non-metallic Inclusions in Titanium-Stabilized AISI 409 Ferritic Stainless Steel

    Science.gov (United States)

    Kruger, Dirk; Garbers-Craig, Andrie

    2017-06-01

    This study describes an investigation into the improvement of castability, final surface quality and formability of titanium-stabilized AISI 409 ferritic stainless steel on an industrial scale. Non-metallic inclusions found in this industrially produced stainless steel were first characterized using SEM-EDS analyses through the INCA-Steel software platform. Inclusions were found to consist of a MgO·Al2O3 spinel core, which acted as heterogeneous nucleation site for titanium solubility products. Plant-scale experiments were conducted to either prevent the formation of spinel, or to modify it by calcium treatment. Modification to spherical dual-phase spinel-liquid matrix inclusions was achieved with calcium addition, which eliminated submerged entry nozzle clogging for this grade. Complete modification to homogeneous liquid calcium aluminates was achieved at high levels of dissolved aluminum. A mechanism was suggested to explain the extent of modification achieved.

  19. Characteristics and Modification of Non-metallic Inclusions in Titanium-Stabilized AISI 409 Ferritic Stainless Steel

    Science.gov (United States)

    Kruger, Dirk; Garbers-Craig, Andrie

    2017-02-01

    This study describes an investigation into the improvement of castability, final surface quality and formability of titanium-stabilized AISI 409 ferritic stainless steel on an industrial scale. Non-metallic inclusions found in this industrially produced stainless steel were first characterized using SEM-EDS analyses through the INCA-Steel software platform. Inclusions were found to consist of a MgO·Al2O3 spinel core, which acted as heterogeneous nucleation site for titanium solubility products. Plant-scale experiments were conducted to either prevent the formation of spinel, or to modify it by calcium treatment. Modification to spherical dual-phase spinel-liquid matrix inclusions was achieved with calcium addition, which eliminated submerged entry nozzle clogging for this grade. Complete modification to homogeneous liquid calcium aluminates was achieved at high levels of dissolved aluminum. A mechanism was suggested to explain the extent of modification achieved.

  20. Effect of the structural parameters changes in the multi-strand tundish on the non-metallic inclusions distribution and separation

    Directory of Open Access Journals (Sweden)

    M. Warzecha

    2014-10-01

    Full Text Available The aim of presented studies was to investigate the fluid flow change and non-metallic inclusions removal changes due to tundish construction modifications. In presented study, numerical simulations were used. Numerical simulations are carried out with the finite-volume commercial code ANSYS Fluent. Steady-state casting conditions for the flow structure and the inclusions removal process are analysed.

  1. Agglomeration of Non-metallic Inclusions at Steel/Ar Interface: In- Situ Observation Experiments and Model Validation

    Science.gov (United States)

    Mu, Wangzhong; Dogan, Neslihan; Coley, Kenneth S.

    2017-10-01

    Better understanding of agglomeration behavior of nonmetallic inclusions in the steelmaking process is important to control the cleanliness of the steel. In this work, a revision on the Paunov simplified model has been made according to the original Kralchevsky-Paunov model. Thus, this model has been applied to quantitatively calculate the attractive capillary force on inclusions agglomerating at the liquid steel/gas interface. Moreover, the agglomeration behavior of Al2O3 inclusions at a low carbon steel/Ar interface has been observed in situ by high-temperature confocal laser scanning microscopy (CLSM). The velocity and acceleration of inclusions and attractive forces between Al2O3 inclusions of various sizes were calculated based on the CLSM video. The results calculated using the revised model offered a reasonable fit with the present experimental data for different inclusion sizes. Moreover, a quantitative comparison was made between calculations using the equivalent radius of a circle and those using the effective radius. It was found that the calculated capillary force using equivalent radius offered a better fit with the present experimental data because of the inclusion characteristics. Comparing these results with other studies in the literature allowed the authors to conclude that when applied in capillary force calculations, the equivalent radius is more suitable for inclusions with large size and irregular shape, and the effective radius is more appropriate for inclusions with small size or a large shape factor. Using this model, the effect of inclusion size on attractive capillary force has been investigated, demonstrating that larger inclusions are more strongly attracted.

  2. Evolution of Ti-Based Nonmetallic Inclusions During Solution Treatment of Maraging 250 Steel: Thermodynamic Calculations and Experimental Verification

    Science.gov (United States)

    Shmulevitsh, Mati; Pinkas, Malki; Weizman, Amir; Frage, Nachum

    2011-06-01

    The evolution of Ti-based nonmetallic inclusions in Maraging 250 steel, namely Ti(CxN1-x) and Ti4C2S2, was investigated experimentally. Their stability in austenite also was analyzed by a thermodynamic analysis of the Fe-Ni-Ti-C-N-S system. It was established that the total concentration of the inclusions decreases from 0.024 pct to 0.008 pct after treatment at 1453 K (1180 °C) for 3 hours. The Ti4C2S2 inclusions completely dissolve in austenite at 1523 K (1250 °C) during 1 hour of treatment. The composition of the carbonitride inclusions is shifted toward higher TiN contents when they dissolve in austenite. Nitrogen-enriched titanium carbonitride inclusions are stable in austenite and their fraction may be reduced only by controlling nitrogen content in the steel. The experimental observations are in good agreement with the results of the thermodynamic analysis.

  3. Effect of Calcium Treatment on Non-Metallic Inclusions in Ultra-Low Oxygen Steel Refined by High Basicity High Al2O3 Sla

    Institute of Scientific and Technical Information of China (English)

    YANG Jun; WANG Xin-hua; JIANG Min; WANG Wan-jun

    2011-01-01

    The influence of calcium treatment on non-metallic inclusions had been studied when control technology of refining top slag in ladle furnace was used in ultra-low oxygen steelmaking. A sufficient amount aluminium was added to experimental heats for final

  4. Deformation and fracture properties of metals with non-metallic inclusions; Verformung und Bruch von Metallen mit nichtmetallischen Einschluessen

    Energy Technology Data Exchange (ETDEWEB)

    Schmauder, S.; Soppa, E. [Stuttgart Univ. (Germany). Staatliche Materialpruefungsanstalt

    1998-12-31

    Microstructural effects due to formation of non-uniform lines of non-metallic inclusions in the matrix are examined with respect to their macro-, meso-, and micromechanical effects in the alloy Al(6061) reinforced by SiC inclusions. A comparative analysis of results obtained with various microstructures reveals essential differences in the formation of shear bands, stress peaks, and strain concentrations in the material structure. The maxima and the distribution of those field variables are determined not only by the arrangement of inclusions clusters in the stringers but also depend on the presence and number of single-particle inclusions in pure matrix material. The banding of the microstructure causes a strongly anisotropic behaviour in terms of stress and strain distributions. (orig./CB) [Deutsch] In diesem Beitrag werden Gefuegeeinfluesse aufgrund unterschiedlich starker zeiliger Anordnungen der Teilchen in der Matrix im Hinblick auf ihre makro-, meso- und mikromechanischen Auswirkungen am Beispiel einer SiC-teilchenverstaerkten Aluminiumlegierung Al(6061) untersucht. Ein Vergleich der Ergebnisse verschiedener Gefuege zeigt wesentliche Unterschiede hinsichtlich der Ausbildung von Scherbaendern, Spannungsspitzen und von Dehnungskonzentrationen im Werkstoffgefuege. Die Maxima und die Verteilung dieser Feldgroessen sind nicht nur abhaengig davon, wie die Teilchen in den Zeilen angeordnet sind, sondern auch davon, ob einzelne Teilchen in reinen Matrixbereichen vorhanden sind. Die Zeiligkeit des Gefueges fuehrt zu einem stark anisotropen Verhalten hinsichtlich Spannungs- und Dehnungsverteilungen. (orig.)

  5. Yttrium modifying influence on the shape and amount of nonmetallic inclusions in the austenitic high alloy steel

    Directory of Open Access Journals (Sweden)

    Андрій Володимирович Патюпкін

    2016-07-01

    Full Text Available Yttrium influence on the form and amount of non-metallic inclusions in steel 06H23N18M5 was studied. It has been found that yttrium binds oxygen and other elements into heterogeneous compounds, it resulting in the transition of impurities into passive state. Oxide inclusions, sulfide inclusions and globules formed as a result of steel components reactions with oxygen, sulfur and nitrogen dissolved in metal are mostly found in the structure. It was found that by modifying and refining austenitic steels with yttrium service properties of the deposited layer can be adjusted. X-ray diffraction and X-ray spectrum analysis revealed that the modified steel 06H23N18M5 + 0.02% Y has a heterogeneous structure with uniformly distributed inclusions of σ-phase and composite carbides (Fe, Cr, Mo 23C6. It is possible that Y modification resulted in the appearance of chemically resistant intermetallic σ-phase in these steels, for nucleation was facilitated by increasing the number of crystallization centers as dispersed primary yttrium oxy-sulfide compounds

  6. Effect of Refractory on Nonmetallic Inclusions in Al-Killed Steel

    Science.gov (United States)

    Deng, Zhiyin; Zhu, Miaoyong; Sichen, Du

    2016-10-01

    To understand the effect of refractory on the evolution of inclusions in the secondary steelmaking, steel samples were taken at different stages of the process train. Laboratory experiments were carried out using different refractories (alumina, spinel, and MgO). In the laboratory study, the types of inclusions considered were alumina, spinel, and calcium aluminate. The focus was given to Al-killed steel. The results showed that alumina refractory and spinel refractory had little effect on all the three types of inclusions, while the effect of MgO refractory depended on the activity of dissolved oxygen in liquid steel. With lower oxygen activity, alumina inclusions could transform into spinel inclusions. No evident change could be found for spinel and calcium aluminate inclusions. When the oxygen activity was high enough, spinel inclusions could not be generated from alumina inclusions. The laboratory results helped in understanding the evolution of the inclusions in the industrial process.

  7. Agglomeration of Non-metallic Inclusions at the Steel/Ar Interface: Model Application

    Science.gov (United States)

    Mu, Wangzhong; Dogan, Neslihan; Coley, Kenneth S.

    2017-08-01

    Inclusion agglomeration is an important element in several industrial problems during steelmaking, such as nozzle clogging. In parallel work by the authors, a revised Kralchevsky-Paunov model has been established and the performance of this model has been validated against the experimental data from in-situ observations using confocal laser scanning microscopy. In this work, the revised model has been applied to quantitatively evaluate the attractive capillary force for the agglomeration of various inclusions at the interface between Ar and liquid iron/steel. A parametric study of the effects on the capillary force of the inclusion density, contact angle between the inclusion and liquid steel, and the surface tension of the liquid metal are quantitatively investigated. The results show that inclusion density and contact angle have a more marked effect on the capillary force than surface tension of liquid metal. Moreover, the inclusion agglomeration behavior in the liquid iron/steel matrix is discussed. The coagulation coefficient of various inclusions is calculated. Both the calculation results of the attractive capillary force of inclusions at the interface between Ar and liquid iron/steel and coagulation coefficient of inclusions in the liquid iron/steel matrix can offer a close agreement; moreover, the order of magnitude of inclusion agglomeration tendency is suggested. By using the coagulation coefficient, the inclusion collision volume and collision rate are calculated and the effects of inclusion composition, size, and number density are investigated. The evaluation results show that the tendency for affecting inclusion collision is inclusion number density > inclusion size > inclusion composition.

  8. The effect of non-metallic inclusions on the fracture toughness master curve in high copper reactor pressure vessel welds

    Science.gov (United States)

    Oh, Yong-Jun; Lee, Bong-Sang; Hong, Jun-Hwa

    2002-03-01

    The fracture toughness of two high copper reactor pressure vessel welds having low upper shelf energy was evaluated in accordance with the master curve method of ASTM E1921. The resultant data were correlated to the metallurgical factors involved in the brittle fracture initiation to provide a metallurgical-based understanding of the master curve. The tests were performed using pre-cracked Charpy V-notched specimens and the master curve was made with an average of T0 values determined at different temperatures. In all specimens, the cleavage fracture initiated at non-metallic inclusion ranging from 0.7 to 3.5 μm in diameter showing a scatter with the specimens and testing temperatures. Temperature dependency of the triggering particle size was not found. The fracture toughness ( KJC) was inversely proportional to the square root of the triggering inclusion diameter ( di) at respective temperatures. From this relationship, we determined median KJC values which correspond to the average value of triggering inclusion diameter of all tested specimens and defined them as a modified median KJC ( K'JC(med) ). The obtained K'JC(med) values showed quite smaller deviation from the master curve at different temperatures than the experimental median KJC values. This suggests that the master curve is on the premise of a constant dimension of key microstructural factor in a material regardless of the testing temperature. But the inclusion size at trigger point played an important role in the absolute position of the master curve with temperature and the consequent T0 value.

  9. The effect of non-metallic inclusions on the fracture toughness master curve in high copper reactor pressure vessel welds

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Yong-Jun E-mail: yjoh@kaeri.re.kr; Lee, Bong-Sang; Hong, Jun-Hwa

    2002-03-01

    The fracture toughness of two high copper reactor pressure vessel welds having low upper shelf energy was evaluated in accordance with the master curve method of ASTM E1921. The resultant data were correlated to the metallurgical factors involved in the brittle fracture initiation to provide a metallurgical-based understanding of the master curve. The tests were performed using pre-cracked Charpy V-notched specimens and the master curve was made with an average of T{sub 0} values determined at different temperatures. In all specimens, the cleavage fracture initiated at non-metallic inclusion ranging from 0.7 to 3.5 {mu}m in diameter showing a scatter with the specimens and testing temperatures. Temperature dependency of the triggering particle size was not found. The fracture toughness (K{sub J{sub C}}) was inversely proportional to the square root of the triggering inclusion diameter (d{sub i}) at respective temperatures. From this relationship, we determined median K{sub J{sub C}} values which correspond to the average value of triggering inclusion diameter of all tested specimens and defined them as a modified median K{sub J{sub C}} (K{sup '}{sub J{sub C}}{sub (med)}). The obtained K{sup '}{sub J{sub C}}{sub (med)} values showed quite smaller deviation from the master curve at different temperatures than the experimental median K{sub J{sub C}} values. This suggests that the master curve is on the premise of a constant dimension of key microstructural factor in a material regardless of the testing temperature. But the inclusion size at trigger point played an important role in the absolute position of the master curve with temperature and the consequent T{sub 0} value.

  10. Investigation on Nonmetallic Inclusions in Ultra-Low-Oxygen Special Steels

    Science.gov (United States)

    Li, Jin Zhu; Jiang, Min; He, Xiao-Fei; Sun, Wei; Wang, Xin-Hua

    2016-08-01

    Investigation was carried out on inclusions in ultra-low-oxygen special steel by taking systematic samplings not only from secondary refining but also from continuous casting. It was found that RH degassing had a much stronger ability than LF refining in removing inclusions. Total oxygen (TO) can be further reduced from 0.0013 to 0.0015 mass pct to about 0.00047 mass pct without too much difficulty by elongating RH degassing time to 33 minute. Inclusions larger than 5 μm were decreased from 1.49 to 0.08 N/mm2 with a removal ratio of about 94 pct. During secondary refining, inclusions experienced continuous evolution from Al2O3 to the MgO-Al2O3, CaO-MgO-Al2O3, and CaO-Al2O3 system due to complex reactions among slag, steel, and refractory materials. Because of more efficient removal of solid inclusions, especially those large ones during RH treatment, thorough modification of solid inclusions into liquid CaO-MgO-Al2O3 can be achieved. Reoxidation during casting resulted in an obvious rise in Al2O3 content in inclusions, which offset the efforts made during secondary refining. Liquid CaO-Al2O3 systems after RH were changed to solid CaO-Al2O3, MgO-Al2O3, or CaO-MgO-Al2O3 again. Large inclusions with sizes approaching several hundred micron were frequently observed in casting bloom by a vast area of scanning under an automatic scanning electron microscope despite very low TO of about 0.00059 mass pct. A total of 78 pct of them were cluster-shaped CaO-MgO-Al2O3 solid inclusions with sizes as large as 200-330 μm. Most clusters over 100 μm were constituted by smaller particles with similar chemical compositions to other small singular inclusions in steel, which indicated that they were formed due to the aggregations of small inclusions during casting. Moreover, the location of them indicated a close relationship to the solidification microstructure of steel, which has not been covered before. It was impressively found that larger inclusions were mainly in the column

  11. Study of the nature of non-metallic inclusions in samples of aluminum and silicon killed low carbon steels, collected in the refining treatment and continuous casting stages

    Directory of Open Access Journals (Sweden)

    José Carlos Santos Pires

    2004-12-01

    Full Text Available The amount, distribution, size and chemical composition of non-metallic inclusions have a direct influence on steel properties. By controlling size and chemical composition of these inclusions, it is possible to get a product with good quality. The identification of the nature and the control of inclusion formation are very important for steel cleanness. The behavior of these inclusions is predictable, in some extent, by the determination of the chemical composition of non-metallic phases that form such inclusions. With the objective of studying the chemical composition, the size and the distribution of such inclusions, samples of aluminum and silicon killed low carbon steels were collected in a national steel industry in the secondary refining and continuous casting stages. These samples were analyzed in the scanning electron microscope (SEM coupled to an energy dispersive analysis system (EDS. From the results, it was possible to evaluate the nature of inclusions and to analyze the effectiveness of the refining process in the reduction of the number and area fraction of the inclusions. It was also possible to verify that the inclusions that remained after treatment, are less damage both to the steel properties as to the continuous casting process (clogging of the submerged valve.

  12. Effect of inhomogeneous distribution of non-metallic inclusions on crack path deflection in G42CrMo4 steel at different loading rates

    Directory of Open Access Journals (Sweden)

    S. Henschel

    2015-10-01

    Full Text Available An inhomogeneous distribution of non-metallic inclusions can result from the steel casting process. The aim of the present study was to investigate the damaging effect of an inhomogeneous distribution of nonmetallic inclusions on the crack extension behavior. To this end, the fracture toughness behavior in terms of quasi-static J-a curves was determined at room temperature. Additionally, dynamic fracture mechanics tests in an instrumented Charpy impact-testing machine were performed. The fracture surface of fracture mechanics specimens was analyzed by means of scanning electron microscopy. It was shown that an inhomogeneous distribution significantly affected the path and, therefore, the plane of crack growth. Especially clusters of non-metallic inclusions with a size of up to 200 μm exhibited a very low crack growth resistance. Due to the damaging effect of the clusters, the growing crack was strongly deflected towards the cluster. Furthermore, crack tip blunting was completely inhibited when inclusions were located at the fatigue precrack tip. Due to the large size of the non-metallic inclusion clusters, the height difference introduced by crack path deflection was significantly larger than the stretch zone height due to the crack tip blunting. However, the crack path deflection introduced by a cluster was not associated with a toughness increasing mechanism. The e dynamic loading ( 1 0.5 5 s MPam 10   K did not result in a transition from ductile fracture to brittle fracture. However, the crack growth resistance decreased with increased loading rate. This was attributed to the higher portion of relatively flat regions where the dimples were less distinct.

  13. The Influence of Technological Parameters of X70 Stainless Steel Ladle Refining on the Residual Content of Non-Metallic Inclusions

    Directory of Open Access Journals (Sweden)

    Babanin A.

    2015-09-01

    Full Text Available It is demonstrated that during secondary refining at the ladle furnace the carbon content of steel and the residence time of the metal in the ladle exert a significant impact on the residual content of non-metallic inclusions (NMI in steel. Mathematical calculations showed that the dynamic forces have minor effect on the motion of small sized NMI, making it difficult to penetrate deep into the slag.

  14. Assessment of Different Turbulence Models for the Motion of Non-metallic Inclusion in Induction Crucible Furnace

    Science.gov (United States)

    Barati, H.; Wu, M.; Kharicha, A.; Ludwig, A.

    2016-07-01

    Turbulent fluid flow due to the electromagnetic forces in induction crucible furnace (ICF) is modeled using k-ɛ, k-ω SST and Large Eddy Simulation (LES) turbulence models. Fluid flow patterns calculated by different turbulence models and their effects on the motion of non-metallic inclusions (NMI) in the bulk melt have been investigated. Results show that the conventional k-ɛ model cannot solve the transient flow in ICF properly. With k-ω model transient flow and oscillation behavior of the flow pattern can be solved, and the motion of NMI can be tracked fairly well. LES model delivers the best modeling result on both details of the transient flow pattern and motion trajectories of NMI without the limitation of NMI size. The drawback of LES model is the long calculation time. Therefore, for general purpose to estimate the dynamic behavior of NMI in ICF both k-ω SST and LES are recommended. For the precise calculation of the motion of NMI smaller than 10 μm only LES model is appropriate.

  15. Detection and Influence of Shrinkage Pores and Nonmetallic Inclusions on Fatigue Life of Cast Aluminum Alloys

    Science.gov (United States)

    Tijani, Yakub; Heinrietz, André; Stets, Wolfram; Voigt, Patrick

    2013-12-01

    In the current study, test bars of cast aluminum alloys EN AC-AlSi8Cu3 and EN AC-AlSi7Mg0.3 were produced with a defined amounts of shrinkage pores and oxides. For this purpose, a permanent mold with heating and cooling devices for the generation of pores was constructed. The oxides were produced by contaminating the melt. The specimens and their corresponding defect distributions were examined and quantified by X-ray computer tomography (CT) and quantitative metallography, respectively. A special test algorithm for the simultaneous image analyses of pores and oxides was developed. Fatigue tests were conducted on the defective samples. It was found that the presence of shrinkage pores lowers the fatigue strength, and only few oxide inclusions were found to initiate fatigue cracks when shrinkage pores are present. The results show that the pore volume is not sufficient to characterize the influence of shrinkage pores on fatigue life. A parametric model for the calculation of fatigue life based on the pore parameters obtained from CT scans was implemented. The model accounts for the combined impact of pore location, size, and shape on fatigue life reduction.

  16. IMPROVEMENT OF CREEP RESISTANCE OF POLYTETRAFLUOROETHYLENE FILMS BY NANO-INCLUSIONS

    Institute of Scientific and Technical Information of China (English)

    Xue-bo Shi; Chun-lei Wu; Min-zhi Rong; Tibor Czigany; Wen-hong Ruan; Ming-qiu Zhang

    2013-01-01

    To improve creep resistance of directional polytetrafluoroethylene (PTFE) films,epoxy grafted nano-SiO2 is mixed with PTFE powder before sintering and calender rolling.The aligned macromolecular chains (especially those in amorphous region) of the composite films can be bundled up by the nanoparticles to share the applied stress together.In addition,incorporation of silica nanoparticles increases crystallinity of PTFE and favors microfibrillation of PTFE in the course of large deformation.As result,PTFE films exhibit lower creep strain and creep rate,and higher tensile strength and hardness.The work is believed to open an avenue for manufacturing high performance fluoropolymers by nano-inclusions.

  17. Effect of inclusions on strain localization during high temperature creep of marble

    Science.gov (United States)

    Rybacki, E.; Morales, L. G.; Naumann, M.; Dresen, G. H.

    2013-12-01

    The deformation of rocks in the Earth's lower crust is often localized in ductile shear zones. Strain localization in rocks deforming at high temperature and pressures may be induced by various physical, chemical, or structurally-related mechanisms. Here, we studied the initiation and propagation of localized deformation in the ductile deformation regime by high temperature deformation experiments on marble with weak or strong inclusions. As starting material we used samples of coarse-grained Carrara marble containing one or two thin artificially prepared sheets of fine-grained Solnhofen limestone or Arkansas novaculite, which act under the applied experimental conditions as soft or strong material heterogeneities, respectively. Samples were deformed in the dislocation creep regime using a Paterson-type gas deformation apparatus at 900°C temperature and confining pressures of 300-400 MPa. Torsion experiments were performed on hollow cylinder samples at a bulk shear strain rate of ≈1.9 x 10-4 s-1 to shear strains γ between 0.02 and 2.9. At low strain, twisted specimens with weak inclusions show minor strain hardening that is replaced by strain weakening at shear strains in excess of ≈0.1- 0.2. Peak shear stress at the imposed condition is about 20MPa, which is ≈8% lower than the strength of inclusion-free samples. Strain progressively localized within the weak inclusions with increasing bulk strain, approaching at γ ≈ 1 a strain ratio of ≈24 with respect to the adjacent matrix strain. This ratio is about half of the strain ratio that is expected from the creep strength contrast between pure marble and limestone at the measured bulk stress. The localization of strain extended into narrow bands in front of the inclusions, where the degree of localization decays exponentially with increasing distance from the tip of the inclusion. Microstructural analysis shows twinning, recrystallization and the development of a strong crystallographic preferred

  18. Determination for the Entrapment Criterion of Non-metallic Inclusions by the Solidification Front During Steel Centrifugal Continuous Casting

    Science.gov (United States)

    Wang, Qiangqiang; Zhang, Lifeng

    2016-06-01

    In the current study, the three-dimensional fluid flow, heat transfer, and solidification in steel centrifugal continuous casting strands were simulated. The volume of fluid model was used to solve the multiphase phenomena between the molten steel and the air. The entrapment and final distribution of inclusions in the solidified shell were studied with the discussion on the effect of rotation behavior of the caster system. Main results indicate that after applying the rotation of the shell, the fluid flow transformed from a recirculation flow to a rotation flow in the mold region and was driven to flow around in the casting direction. As the distance below the meniscus increased, the distribution of the tangential speed of the flow and the centrifugal force along one diameter of the strand became symmetrical gradually. The jet flow from the nozzle hardly impinged on the same location on the shell due to the rotation of the shell during solidification. Thus, the shell thickness on the same height was uniform around, and the thinning shell and a hot spot on the surface of shell were avoided. Both of the measurement and the calculation about the distribution of oxide inclusions along the radial direction indicated the number of inclusions at the side and the center was more than that at the quarter on the cross section of billet. With a larger diameter, inclusions tended to be entrapped toward the center area of the billet.

  19. Rare earth metals influence on morphology of non-metallic inclusions and mechanism of GP240GH and G17CrMo5-5cast steel cracking

    Directory of Open Access Journals (Sweden)

    M. Gajewski

    2009-10-01

    Full Text Available This paper presents results of research carried out in order to specify the influence of the rare earth metals on the morphology of the occuring non-metallic inclusions as well as on the cracking mechanism of GP240GH cast carbon steel and G17CrMo5-5 (0.18%C, 1.2%Cr, 0.53%Mo high temperature cast steel. The tests have been performed on successive industrial melts adding rare earth metals to the ladle during tapping of heat melt from the furnace. It was found that ball-shaped non-metalic inclusions occuring as a result of the rare earth metals influence are heterogenic and they significantly influence the cracking mechanism of Charpy specimens and the impact strength. The morphology of the specimens fracture surface has been substantially changed as a result of the rare earth metals modification. The impact strength of the tested cast carbon steel increased from 100 J/cm2 to ca 155 J/cm2, and the high-temperature cast steel from 30 J/cm2 to ca 100 J/cm2.

  20. Research on the Non-metallic Inclusion in X70 Pipeline Cast Slab%X70管线钢铸坯中非金属夹杂物的研究

    Institute of Scientific and Technical Information of China (English)

    吴雨晨; 李俊国; 闫小林; 李守章; 曾亚南

    2009-01-01

    利用大样电解、金相观测、扫描电镜(SEM)和电子探针(EPMA)等手段,对X70管线钢铸坯中夹杂物的数量、粒径、形貌及组分进行了研究.结果表明:X70管线钢铸坯中夹杂物数量较多,粒径较大,且多为复合夹杂.针对大型夹杂物中硫化物、氧化物、硅铝酸盐和钙铝酸盐复合夹杂的特点,分析了铸坯中夹杂物的主要来源.%Utilizing the methods of sample-electrolysing, metallographic observation, SEM and EPMA, the quantity, dimension, morphologies and composition of non-metallic inclusions in X70 pipeline steel cast slab were investigated. It was suggested that there were larger amount of inclusions with larger diam-eter in the cast slab. Most of these inclusions were complex, such as sulfide, oxide, silicon aluminates and calcium aluminates inclusions. According to the characteristics of inclusions in the east slab, the ma-jor sources of different inclusions were analyzed and explored.

  1. 超低氧齿轮钢非金属夹杂物控制热力学计算及应用%Thermodynamic Calculation and Application of Non-Metallic Inclusions for Ultra-Low-Oxygen Gear Steel

    Institute of Scientific and Technical Information of China (English)

    陈天明

    2011-01-01

    利用热力学软件计算了齿轮钢氧含量与夹杂物成分的关系、夹杂物转变条件.结果表明,超低氧20CrMoH钢中具有较高塑性的非金属夹杂物成分(质量分数)为:SiO2 0~10%,Al2O3 22%~55%,CaO 42%~60%,MgO 5%~10%,与之平衡的时钢液中铝质量分数在0.020%左右,钙质量分数大于0.7×10-6,氧质量分数在0.000 5%左右.选择组成:w(CaO)>40%,w(Al2O3)≤37%,w(MgO)为10%,(w(CaO)+w(MgO))/w(SiO2)为10,SiO2含量尽量低的渣系,钢中Al2O3、MgO·Al2O3夹杂物可转变为低熔点的钙铝酸盐.%Interrelations between oxygen content of gear steel and non-metallic inclusions, and transformations conditions for non-metallic inclusions were calculated using the thermodynamic calculation software Factsage. It is found that the components of non-metallic inclusions with higher plasticity in ultra-low-oxygen gear steel should be composed by SiO2 0-10%, Al2O3 22%-55%, CaO 42%-60%, and MgO 5%-10%, aluminum content would be about 0.020%, calcium content would be more than 0.7 × 10-6 , and oxygen content would be about 0.0005 % in molten steel when the reaction between the inclusion and liquid steel arrived in equilibrium. If the compositions of fining slag with w(CaO)>40%, w(Al2O3 )≤37% ,w(MgO) = 10% ,(w(CaO) +w(MgO))/w(SiO2 ) = 10, and SiO2 content as low as possible were selected, Al2O3 and MgO · Al2O3 in molten steel can transform into calcium aluminates with low melting point.

  2. Fractal Dimension Study of Non-metallic Inclusion Images in Steel%钢中非金属夹杂物图像分形维数的研究

    Institute of Scientific and Technical Information of China (English)

    岳强; 张雅丽; 孔辉; 周俐; 王建军; 汪诚

    2012-01-01

    Binary images of non-metallic inclusions boundary were obtained by processing images of rolling material of 304/304L stainless steel with large inclusions and ingots with micro inclusions. Box-counting method was employed to compute fractal dimension of inclusion contour. Algorithm was implemented with MATLAB programming. Results show that the fractal dimension of inclusion is closely related to its composition and melting point. Morphologies of low melting point Al2O3-SiO2-CaO compound inclusion are sphere or similar sphere, their fractal dimensions are small, morphologies of high melting point Al2O3 inclusions and SiO2 inclusions are irregular, their fractal dimensions are large.%通过对304/304L不锈钢轧材中大型夹杂物和铸锭中显微夹杂物的图像进行处理,得到夹杂物边界的二值图像.采用计盒维数法对夹杂物轮廓的分形维数进行计算与分析,算法利用MATLAB编程实现.结果表明,夹杂物的分形维数与其组成和熔点密切相关,低熔点的Al2O3-SiO2-CaO系复合夹杂的形貌多为球形或类球形,其分形维数较小;高熔点的Al2O3夹杂物与SiQ2夹杂物的形貌多为不规则形,其分形维数较大.

  3. 304奥氏体不锈钢铸锭中非金属夹杂物研究%Research on Non-metallic Inclusions in 304 Austenitic Stainless Steel Ingot

    Institute of Scientific and Technical Information of China (English)

    张雅丽; 王建军; 罗林根; 郭上型; 孔辉; 周俐

    2011-01-01

    The type and the amount of the non-metallic inclusions in 304 stainless steel ingot were investigated, with a tracer used to find out the origin of inclusion. The results show that most of the micro inclusions are Al2Or-SiO2-CaO system inclusions, the micro inclusions (<5 urn) coexit amount of MgO-Al2O3 spinel inclusions;the macro inclusion is main to have two types of compound admixture, respectively is the type of Al2O3-SiOr-CaO.the type of Al2O3-SiO2; one of the main source of the non-matallic inclusions is the slag for the refractory corrosion in the molten steel during tapping; ladle lining affects slightly.%研究304不锈钢铸锭中非金属夹杂物的类型和数量,通过示踪剂分析不锈钢中夹杂物的来源.结果表明:不锈钢铸锭中显微夹杂物主要是以Al2O3-SiO2-CaO系硅酸盐夹杂为主,粒度<5μm的显微夹杂物中同时存在大量的镁铝尖晶石夹杂;大型夹杂物主要有两类复合夹杂物Al2O3-SiO2-CaO系夹杂、Al2O3-SiO2系夹杂;汤道耐火材料的侵蚀是夹杂物主要来源之一,钢包耐火材料对夹杂生成的影响微弱.

  4. Mathematical Modeling on the Growth and Removal of Non-metallic Inclusions in the Molten Steel in a Two-Strand Continuous Casting Tundish

    Science.gov (United States)

    Ling, Haitao; Zhang, Lifeng; Li, Hong

    2016-10-01

    In the current study, mathematical models were developed to predict the transient concentration and size distribution of inclusions in a two-strand continuous casting tundish. The collision and growth of inclusions were considered. The contribution of turbulent collision and Stokes collision was evaluated. The removal of inclusions from the top surface was modeled by considering the properties of inclusions and the molten steel, such as the wettability, density, size, and interfacial tension. The effect of composition of inclusions on the collision of inclusions was included through the Hamaker constant. Meanwhile, the effect of the turbulent fluctuation velocity on the removal of inclusions at the top surface was also studied. Inclusions in steel samples were detected using automatic SEM Scanning so that the amount, morphology, size, and composition of inclusions were achieved. In the simulation, the size distribution of inclusions at the end steel refining was used as the initial size distribution of inclusions at tundish inlet. The equilibrium time when the collision and coalescence of inclusions reached the steady state was equal to 3.9 times of the mean residence time. When Stokes collision, turbulent collision, and removal by floating were included, the removal fraction of inclusions was 16.4 pct. Finally, the removal of solid and liquid inclusions, such as Al2O3, SiO2, and 12CaO·7Al2O3, at the interface between the molten steel and slag was studied. Compared with 12CaO·7Al2O3 inclusions, the silica and alumina inclusions were much easier to be removed from the molten steel and their removal fractions were 36.5 and 39.2 pct, respectively.

  5. Research on Behavior of Non-metallic Inclusions in GCr15 Bearing Steel%GCr15轴承钢中非金属夹杂物行为的研究

    Institute of Scientific and Technical Information of China (English)

    张仰东; 吴晓东; 谈盛康

    2011-01-01

    Based on the productive process of BOF→LF→RH→CC for GCr15 bearing steel produced in Huaigang steel, using metallography and SEM-EDS analysis, the non-metallic inclusions in molten steel were studied in the size, composition and morphology. The changing about the inclusions in the bearing steel were investigated at different refining slag basicity. The main inclusions in rolling were mixed oxides and sulfide. The component diagram of inclusions were analyzed and calculated. The results show that micro-inclusions reduce from 23.34 number/mm2 into 14.02 number /mm2 after LF refining. Inclusions decrease slightly after RH treatment. The quantity of inclusions decrease slightly in rolling process. With the smelting process carrying out, the large inclusions are effectively removed by the steel flowing in ladle movement. The main inclusions in the steel are oxides, sulfide and CaO(CaS)-Al2O3-MgO complex inclusions.%针对淮钢80t转炉-90tLF- 100tRH-CC工艺生产的GCr15轴承钢,采用金相、SEM和EDS等方法,研究了精炼过程中夹杂物的尺寸、成分和形貌等的变化情况.经分析计算,得出了各工序夹杂物的成分图,并分析了夹杂物在冶炼过程中的变化规律.结果表明,在LF炉精炼后,微观夹杂物由23.34个/mm2下降到14.02个/mm2;经RH循环脱气处理后,夹杂物有所减少,成材中,夹杂物数量略有减少;随着冶炼过程的进行,大颗粒夹杂在钢包中随着钢流的运动得到了有效去除,细微夹杂物所占比例逐步升高;钢中存在的夹杂物主要有氧化物、硫化物以及CaO(CaS)-Al2O3-MgO类复合夹杂物.

  6. Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue.

    Science.gov (United States)

    Zhang, Tiantian; Jiang, Jun; Britton, Ben; Shollock, Barbara; Dunne, Fionn

    2016-05-01

    A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270-1480 MPa.

  7. 钢中非金属夹杂物的形成及评判浅析%ANALYSIS OF FORMATION AND EVALUATION OF NON-METALLIC INCLUSIONS IN STEEL

    Institute of Scientific and Technical Information of China (English)

    瞿国鸿; 何开文; 张全新

    2014-01-01

    本文阐述了钢中非金属夹杂物的形成、分类及来源,以及非金属夹杂物数量、尺寸对钢材性能的影响,对评判非金属夹杂物的国家标准GB/T 10561新旧两个版本即2005版和1989版进行比较,分析了氮化物等沉淀相的特性及其对钢材的强化作用,阐明了2005版标准中关于将氮化物、碳化物、碳氮化合物、硼化物定性描述为沉淀相而不作为非金属夹杂物的评判是适宜的。%This paper describes the formation , classification and source of non -metallic inclusions in steel , and the influence of their quantity and size on the performance of steels .It compares the commons and differences between the new National Standard GB /T10561 2005 version with the old 1989 version for evaluating non-metallic inclusions , and analyzes the characteristics of the precipitated phase such as the nitride and the strengthening effect to the steel , and explains that it is appropriate to evaluate ni-trides, carbides, hydrocarbons and boride as precipitated phase not as non -metallic inclusions.

  8. Analysis of non-metallic inclusions in steel by SEM/EDS experiences with the technique as applied to the plain carbon steel Cf53 (1.1213); Analyse nichtmetallischer Einschluesse in Stahl mittels REM/EDS und Anwendung auf den unlegierten Kohlenstoffstahl Cf53 (1.1213)

    Energy Technology Data Exchange (ETDEWEB)

    Lietzau, Jens [GKN Driveline International GmbH, Lohmar (Germany). Research and Product Development Centre

    2010-12-15

    The SEM/EDS provides detailed information on the chemical nature of the non-metallic inclusions present in a steel. However, this information cannot be accepted uncritically. There can be positive and negative preparation artefacts and inclusions might be mis-classified because some elements are not or wrongly identified. Also, this detailed information comes at the cost of considerably longer measurement times than automated LM inclusion analyses require, since LM image acquisition is faster and no time is spent on EDS. (orig.)

  9. Interaction mechanism of non-metallic particles with crystallization front

    Directory of Open Access Journals (Sweden)

    Żak P. L.

    2017-03-01

    Full Text Available The process of steel solidification in the CCS mould is accompanied by a number of phenomena relating to the formation of non-metallic phase, as well as the mechanism of its interaction with the existing precipitations and the advancing crystallization front. In the solidification process the non-metallic inclusions may be absorbed or repelled by the moving front. As a result a specific distribution of non-metallic inclusions is obtained in the solidified ingot, and their distribution is a consequence of these processes. The interaction of a non-metallic inclusion with the solidification front was analyzed for alumina, for different values of the particle radius. The simulation was performed with the use of own computer program. Each time a balance of forces acting on a particle in its specific position was calculated. On this basis the change of position of alumina particle in relation to the front was defined for a specific radius and original location of the particle with respect to the front.

  10. Seismic Creep

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden erupture associated with an earthquake. It is a usually slow deformation...

  11. Creeping eruption

    Science.gov (United States)

    ... are infected. Symptoms Symptoms of creeping eruption include: Blisters Itching , may be more severe at night Raised, ... enter the body through bare feet, so wearing shoes in areas where hookworm infestations are known to ...

  12. 切割丝用盘条非金属夹杂物对比分析%Contrast on non-metallic inclusions control in wire rods for saw wire

    Institute of Scientific and Technical Information of China (English)

    王昆鹏; 姜敏; 赵昊乾; 王新华; 王郢

    2016-01-01

    Inclusions in wire rods for saw wire produced in Kobe steel and a steel works of China were investigated by means of automatic analysis technology using Aspex Explorer. Inclusion size,number density,composition and morphol-ogy were studied systematically. The results show that the inclusions of wire rods from Kobe steel are in a low amount and the size is less than 5μm on cross section. There are two type inclusions in Kobe wire rods,namely,the SiO2 rich SiO2-MnO-Al2O3-(R2O,R=Na、K) type and the low melting point CaO-SiO2-Al2O3-MnO-(MgO) type,both of them are elongat-ed during rolling and are nearly harmless. Inclusions of wire rods from China are also classified into two types:SiO2-MnO-Al2O3 and CaO-SiO2-Al2O3-MnO-(MgO). The inclusions in wire rods from China are not only in lager amount but al-so in worse deformability. The inclusions more than 5μm in size were observed on cross section of wire rods from China. Chemical analysis shows w([Al]s) is 0.000 4%-0.000 6% and w(T[O]) is 0.001 2%-0.001 3% in Kobe wire rod while w([Al]s) is 0.000 4%-0.000 6%and w(T[O]) is 0.001 2%-0.001 3%in domestic ones.%借助Aspex Explorer全自动分析技术对日本神户制钢和国内某钢铁厂所产切割丝用盘条的夹杂物分析检测,详细讨论氧化物夹杂的尺寸、数量密度、成分以及形态.结果表明:神户所产盘条中夹杂物数量少、横截面尺寸均在5μm以下,存在两类夹杂物,即富SiO2的SiO2-MnO-Al2O3-(R2O,R=Na、K)系和低熔点的CaO-SiO2-Al2O3-MnO-(MgO)系夹杂物,两类夹杂物沿轧向均能很好变形,国内某厂所产盘条中夹杂物也分为两类:SiO2-MnO-Al2O3以及CaO-SiO2-Al2O3-MnO-(MgO),夹杂物数量多,变形差且检测到横截面尺寸5μm以上的夹杂物.盘条化学成分分析表明,神户盘条中w([Al]s)为0.000 4%~0.000 6%,w(T[O])为0.001 2%~0.001 3%,国内盘条w([Al]s)为0.000 5%~0.000 6%,w(T[O])为0.001 5%~0.001 6%.

  13. 46 CFR 182.720 - Nonmetallic piping materials.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Nonmetallic piping materials. 182.720 Section 182.720... TONS) MACHINERY INSTALLATION Piping Systems § 182.720 Nonmetallic piping materials. (a) Rigid... systems where permitted by paragraph (e) of this section. (c) Nonmetallic piping must not be used...

  14. 46 CFR 119.720 - Nonmetallic piping materials.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Nonmetallic piping materials. 119.720 Section 119.720 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING MORE... Piping Systems § 119.720 Nonmetallic piping materials. Nonmetallic piping materials,...

  15. 49 CFR 193.2187 - Nonmetallic membrane liner.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Nonmetallic membrane liner. 193.2187 Section 193... GAS FACILITIES: FEDERAL SAFETY STANDARDS Design Lng Storage Tanks § 193.2187 Nonmetallic membrane liner. A flammable nonmetallic membrane liner may not be used as an inner container in a storage tank....

  16. Study of porosity tendency in the Cr-Ni austenitic weld based on inclusion's characteristic in the droplet

    Institute of Scientific and Technical Information of China (English)

    孙咸; 王红鸿; 张汉谦; 王宝

    2004-01-01

    The effect of nonmetallic inclusions in the droplet of the stainless steel covered electrode on the porosity was researched.The result shows that the nonmetallic inclusions in the droplet are spherical,their composition is different from the one of slag and the inclusions have the character of "inner formation".When the ratio of rutile to ilmenite in the coated material is increased, the droplet becomes coarse, the content of nonmetallic inclusion in the droplet decreases,and the porosity sensitivity in the weld metal also decreases.When the ratio of fledspar to ilmenite in the coated material is increased, the droplet becomes fine,the content of nonmetallic inclusion in the droplet increases, and the porosity sensitivity in the weld metal increases. When the ratio of Fe2O3 to ilmenite in the coated material is increased, the droplet becomes fine, the content of nonmetallic inclusion decreases, while the porosity sensitivity does not reduce.

  17. Motion behavior of non-metallic particles under high frequency magnetic field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhong-tao; GUO Qing-tao; YU Feng-yun; LI Jie; ZHANG Jian; LI Ting-ju

    2009-01-01

    Non-metallic particles, especially alumina, are the main inclusions in aluminum and its alloys. Numerical simulation and the corresponding experiments were carried out to study the motion behavior of alumina particles in commercial pure aluminum under high frequency magnetic field. At the meantime, multi-pipe experiment was also done to discuss the prospect of continuous elimination of non-metallic particles under high frequency magnetic field. It is shown that: 1) results of numerical simulation are in good agreement with the experimental results, which certificates the rationality of the simulation model; 2) when the intensity of high frequency magnetic field is 0.06 T, the 30 μm alumina particles in melt inner could migrate to the edge and be removed within 2 s; 3) multi-pipe elimination of alumina particles under high frequency magnetic field is also effective and has a good prospect in industrial application.

  18. Creep in structures

    Energy Technology Data Exchange (ETDEWEB)

    Zyczkowski, M. (Krakow Univ. of Technology (Poland). Inst. of Mechanics and Machine Design) (ed.)

    1991-01-01

    This volume contains 81 papers divided into three almost equal parts: Constitutive equations, combined loadings; damage, creep crack growth, creep rupture; structures, analytical and numerical methods, optimal design. (orig.).

  19. Simultaneous consolidation and creep

    DEFF Research Database (Denmark)

    Krogsbøll, Anette

    1997-01-01

    Materials that exhibit creep under constant effective stress typically also show rate dependent behavior. The creep deformations and the rate sensitive behavior is very important when engineering and geological problems with large time scales are considered. When stress induced compaction...

  20. Simultaneous consolidation and creep

    DEFF Research Database (Denmark)

    Krogsbøll, Anette

    1997-01-01

    Materials that exhibit creep under constant effective stress typically also show rate dependent behavior. The creep deformations and the rate sensitive behavior is very important when engineering and geological problems with large time scales are considered. When stress induced compaction...... (consolidation) is retarded by slow drainage of excess pore pressure it is expected that consolidation and creep occur simultaneously. A constitutive model adressing the problems of rate sensitive behavior and simultaneous consolidation and creep is presented....

  1. Low temperature creep plasticity

    Directory of Open Access Journals (Sweden)

    Michael E. Kassner

    2014-07-01

    Full Text Available The creep behavior of crystalline materials at low temperatures (T < 0.3Tm is discussed. In particular, the phenomenological relationships that describe primary creep are reviewed and analyzed. A discussion of the activation energy for creep at T < 0.3Tm is discussed in terms of the context of higher temperature activation energy. The basic mechanism(s of low temperature creep plasticity are discussed, as well.

  2. Creep in ceramics

    CERN Document Server

    Pelleg, Joshua

    2017-01-01

    This textbook is one of its kind, since there are no other books on Creep in Ceramics. The book consist of two parts: A and B. In part A general knowledge of creep in ceramics is considered, while part B specifies creep in technologically important ceramics. Part B covers creep in oxide ceramics, carnides and nitrides. While covering all relevant information regarding raw materials and characterization of creep in ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  3. Sustainable Non-Metallic Building Materials

    Directory of Open Access Journals (Sweden)

    Svetlana Tretsiakova-McNally

    2010-01-01

    Full Text Available Buildings are the largest energy consumers and greenhouse gases emitters, both in the developed and developing countries. In continental Europe, the energy use in buildings alone is responsible for up to 50% of carbon dioxide emission. Urgent changes are, therefore, required relating to energy saving, emissions control, production and application of materials, use of renewable resources, and to recycling and reuse of building materials. In addition, the development of new eco-friendly building materials and practices is of prime importance owing to the growing environmental concerns. This review reflects the key tendencies in the sector of sustainable building materials of a non-metallic nature that have occurred over the past decade or so.

  4. Creep in amorphous metals

    Directory of Open Access Journals (Sweden)

    Michael E. Kassner

    2015-01-01

    Full Text Available This paper reviews the work on creep behavior of amorphous metals. There have been, over the past several years, a few reviews of the mechanical behavior of amorphous metals. Of these, the review of the creep properties of amorphous metals by Schuh et al. though oldest of the three, is particularly noteworthy and the reader is referred to this article published in 2007. The current review of creep of amorphous metals particularly focuses on those works since that review and places the work prior to 2007 in a different context where new developments warrant.

  5. Thermodynamic aspects of inclusion engineering in steels

    Institute of Scientific and Technical Information of China (English)

    A. Costa e Silva

    2006-01-01

    Tailoring non-metallic inclusions in accordance to the desired effect on steel properties has gained widespread acceptance in the last decades and has become known as "inclusion engineering". Effective inclusion engineering involves three steps: (a) a good knowledge of how inclusions influence properties, (b) understanding what is the effect of each type of inclusions on these properties and thus which is the most desirable inclusion in a given product and (c) adjusting the processing parameters to obtain these inclusions. A significant portion of the process adjustment is done during steel refining, where the steel can be tailored so that the desired chemical composition of the non-metallic inclusions that will precipitate can be altered. Understanding the relations between steel chemistry, processing variables and inclusion chemical composition requires significant understanding of the thermodynamics of the systems involved. These complex equilibrium calculations are best done using computational thermodynamics. In this work some of the basic techniques used to control inclusion composition are reviewed and the thermodynamic information required to perform this task is presented. Several examples of the application of computational thermodynamics to inclusion engineering of different steels grades are presented and compared with experimental results, whenever possible. The potential and limitations of the method are highlighted, in special those related to thermodynamic data and databases.

  6. DETERMINATION OF CREEP PARAMETERS FROM INDENTATION CREEP EXPERIMENTS

    Institute of Scientific and Technical Information of China (English)

    岳珠峰; 万建松; 吕震宙

    2003-01-01

    The possibilities of determining creep parameters for a simple Norton law material are explored from indentation creep testing. Using creep finite element analysis the creep indentation test technique is analyzed in terms of indentation rates at constant loads. Emphasis is placed on the relationships between the steady creep behavior of indentation systems and the creep property of the indented materials. The role of indenter geometry, size effects and macroscopic constraints is explicitly considered on indentation creep experiments. The influence of macroscopic constraints from the material systems becomes important when the size of the indenter is of the same order of magnitude as the size of the testing material. Two methods have been presented to assess the creep property of the indented material from the indentation experimental results on the single-phase-material and two-phase-material systems. The results contribute to a better mechanical understanding and extending the application of indentation creep testing.

  7. Nitrogen hardening of creep-resistant G-NiCr28W alloy

    Directory of Open Access Journals (Sweden)

    Z. Pirowski

    2010-07-01

    Full Text Available In the group of creep-resistant materials, most important are heat-resistant nickel-based alloys. The G-NiCr28W alloy subject to detailed examinations was observed to have two different austenite-like phases. In the interdendritic spaces of alloy matrix, the presence of another phase, also characterised by paramagnetic properties, was detected. Inside this interdendritic phase, local areas of a lamellar structure, composed of both of the above mentioned phases, were present. Nitrogen treatment was observed to raise the microhardness of both these phases.The presence of nitrogen made the regions of a lamellar structure disappear completely. Their place was occupied by precipitates dispersed in the matrix, and occasionally forming large clusters.It has been observed that cold work can harden the G-NiCr28W alloy to a very small degree only, in spite of the fact that hardness isincreasing systematically with the increasing degree of cold work. The said alloy, when enriched with nitrogen added as an alloyingelement, is characterised by hardness higher than the hardness of its nitrogen-free counterpart. The value of hardness is increasing evenmore under the effect of low-degree cold work, although increasing further the degree of cold work seems to have no effect on hardnessincrease. The problem faced in nickel-based materials is the possibility of making defect-free castings from alloys with high nitrogen content. Alloys investigated in the present study were remelted, cast and subject to solidification under high nitrogen pressure in the furnace chamber. However, melting carried out under these conditions could not prevent the occurrence of non-metallic inclusions which, while being unable to pass to a riser, formed local clusters or even thin films, resulting in numerous microcracks or discontinuities encompassing large regions of the casting. This problem seems to be of major concern and is the first one to require prompt solution in the currently

  8. Biaxial Creep Specimen Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    JL Bump; RF Luther

    2006-02-09

    This report documents the results of the weld development and abbreviated weld qualification efforts performed by Pacific Northwest National Laboratory (PNNL) for refractory metal and superalloy biaxial creep specimens. Biaxial creep specimens were to be assembled, electron beam welded, laser-seal welded, and pressurized at PNNL for both in-pile (JOYO reactor, O-arai, Japan) and out-of-pile creep testing. The objective of this test campaign was to evaluate the creep behavior of primary cladding and structural alloys under consideration for the Prometheus space reactor. PNNL successfully developed electron beam weld parameters for six of these materials prior to the termination of the Naval Reactors program effort to deliver a space reactor for Project Prometheus. These materials were FS-85, ASTAR-811C, T-111, Alloy 617, Haynes 230, and Nirnonic PE16. Early termination of the NR space program precluded the development of laser welding parameters for post-pressurization seal weldments.

  9. 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.

  10. Creep Resistant Zinc Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  11. Creep Resistant Zinc Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  12. Investigation of the effect of aggregates' morphology on concrete creep properties by numerical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Lavergne, F. [Université Paris-Est, Laboratoire Navier (ENPC, IFSTTAR, CNRS), 77455 Marne-la-Vallée Cedex (France); Sab, K., E-mail: karam.sab@enpc.fr [Université Paris-Est, Laboratoire Navier (ENPC, IFSTTAR, CNRS), 77455 Marne-la-Vallée Cedex (France); Sanahuja, J. [Département Mécanique des Matériaux et des Composants, EDF R& D, Site des Renardières, Avenue des Renardières, 77818 Moret-Sur-Loing Cedex (France); Bornert, M. [Université Paris-Est, Laboratoire Navier (ENPC, IFSTTAR, CNRS), 77455 Marne-la-Vallée Cedex (France); Toulemonde, C. [Département Mécanique des Matériaux et des Composants, EDF R& D, Site des Renardières, Avenue des Renardières, 77818 Moret-Sur-Loing Cedex (France)

    2015-05-15

    Prestress losses due to creep of concrete is a matter of interest for long-term operations of nuclear power plants containment buildings. Experimental studies by Granger (1995) have shown that concretes with similar formulations have different creep behaviors. The aim of this paper is to numerically investigate the effect of size distribution and shape of elastic inclusions on the long-term creep of concrete. Several microstructures with prescribed size distribution and spherical or polyhedral shape of inclusions are generated. By using the 3D numerical homogenization procedure for viscoelastic microstructures proposed by Šmilauer and Bažant (2010), it is shown that the size distribution and shape of inclusions have no measurable influence on the overall creep behavior. Moreover, a mean-field estimate provides close predictions. An Interfacial Transition Zone was introduced according to the model of Nadeau (2003). It is shown that this feature of concrete's microstructure can explain differences between creep behaviors.

  13. Test plan for the irradiation of nonmetallic materials.

    Energy Technology Data Exchange (ETDEWEB)

    Brush, Laurence H.; Farnum, Cathy Ottinger; Dahl, M.; Joslyn, C. C.; Venetz, T. J.

    2013-05-01

    A comprehensive test program to evaluate nonmetallic materials use in the Hanford tank farms is described in detail. This test program determines the effects of simultaneous multiple stressors at reasonable conditions on in-service configuration components by engineering performance testing.

  14. Test plan for the irradiation of nonmetallic materials.

    Energy Technology Data Exchange (ETDEWEB)

    Brush, Laurence H.; Farnum, Cathy Ottinger; Gelbard, Fred; Dahl, M.; Joslyn, C. C.; Venetz, T. J.

    2013-03-01

    A comprehensive test program to evaluate nonmetallic materials use in the Hanford Tank Farms is described in detail. This test program determines the effects of simultaneous multiple stressors at reasonable conditions on in-service configuration components by engineering performance testing.

  15. Industrial application of liquid steel filtration out of dispersed nonmetallic phase in the continuous casting machine

    Directory of Open Access Journals (Sweden)

    K. Janiszewski

    2013-01-01

    Full Text Available Hitherto existing investigations concerning the ceramic filter use in the steel making processes (both of laboratory and industrial scale have given good results. The obtained results of filtration (in the laboratory have proved that this method may be used as an effective and cheap way of steel filtration from non-metallic inclusions. Placing filters in the tundish is the best location in consideration of limiting the possibility of secondary pollution of steel. Yet, the results presented in this paper, of an experiment prepared and carried out in the industrial environment, are the only positive results obtained, which are connected with so much quantities of liquid steel processed with use of the multi-hole ceramic filters.

  16. Creep behavior of microbiotic crust

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The creep behavior of microbiotic crust at room temperature was revealed by the creep bending tests of cantilever beam under constant-load conditions.The variation in the deflection with time can be depicted well by a standard creep curve.Creep rupture is a fundamental failure mechanism of microbiotic crust due to creep.A simple theory was then applied to describe this new me-chanical behavior.The existence of creep phenomenon brings into question the validity of widely used methods for measuring the strength of microbiotic crust.

  17. Creep of fibrous composite materials

    DEFF Research Database (Denmark)

    Lilholt, Hans

    1985-01-01

    Models are presented for the creep behaviour of fibrous composite materials with aligned fibres. The models comprise both cases where the fibres remain rigid in a creeping matrix and cases where the fibres are creeping in a creeping matrix. The treatment allows for several contributions to the cr......Models are presented for the creep behaviour of fibrous composite materials with aligned fibres. The models comprise both cases where the fibres remain rigid in a creeping matrix and cases where the fibres are creeping in a creeping matrix. The treatment allows for several contributions...... such as Ni + W-fibres, high temperature materials such as Ni + Ni3Al + Cr3C2-fibres, and medium temperature materials such as Al + SiC-fibres. For the first two systems reasonable consistency is found for the models and the experiments, while for the third system too many unquantified parameters exist...

  18. Deterministic Multiaxial Creep and Creep Rupture Enhancements for CARES/Creep Integrated Design Code

    Science.gov (United States)

    Jadaan, Osama M.

    1998-01-01

    High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep rupture criterion. However, that model did not take into account the deteriorating state of the material due to creep damage (e.g., cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial creep curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of sum, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions This creep life prediction methodology was preliminarily added to the integrated design code CARES/Creep (Ceramics Analysis and Reliability Evaluation of Structures/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of Ns methodology and the

  19. Cutting of nonmetallic materials using Nd:YAG laser beam

    Institute of Scientific and Technical Information of China (English)

    Bashir Ahmed Tahir; Rashid Ahmed; M. G. B. Ashiq; Afaq Ahmed; M. A. Saeed

    2012-01-01

    This study deals with Nd:YAG laser cutting nonmetallic materials,which is one of the most important and popular industrial applications of laser.The main theme is to evaluate the effects of Nd:YAG laser beam power besides work piece scanning speed.For approximate cutting depth,a theoretical study is conducted in terms of material property and cutting speed.Results show a nonlinear relation between the cutting depth and input energy.There is no significant effect of speed on cutting depth with the speed being larger than 30 mm/s.An extra energy is utilized in the deep cutting.It is inferred that as the laser power increases,cutting depth increases.The experimental outcomes are in good agreement with theoretical results.This analysis will provide a guideline for laser-based industry to select a suitable laser for cutting,scribing,trimming,engraving,and marking nonmetallic materials.

  20. System definition study of deployable, non-metallic space structures

    Science.gov (United States)

    Stimler, F. J.

    1984-01-01

    The state of the art for nonmetallic materials and fabrication techniques suitable for future space structures are summarized. Typical subsystems and systems of interest to the space community that are reviewed include: (1) inflatable/rigidized space hangar; (2) flexible/storable acoustic barrier; (3) deployable fabric bulkhead in a space habitat; (4) extendible tunnel for soft docking; (5) deployable space recovery/re-entry systems for personnel or materials; (6) a manned habitat for a space station; (7) storage enclosures external to the space station habitat; (8) attachable work stations; and (9) safe haven structures. Performance parameters examined include micrometeoroid protection; leakage rate prediction and control; rigidization of flexible structures in the space environment; flammability and offgassing; lifetime for nonmetallic materials; crack propagation prevention; and the effects of atomic oxygen and space debris. An expandable airlock for shuttle flight experiments and potential tethered experiments from shuttle are discussed.

  1. Synthesis of aromatic nitriles using nonmetallic cyano-group sources.

    Science.gov (United States)

    Kim, Jinho; Kim, Hyun Jin; Chang, Sukbok

    2012-11-26

    Aromatic nitriles are prepared efficiently through transition-metal-mediated cyanation of aryl (pseudo)halides with metallic cyano-group sources, such as CuCN, KCN, NaCN, Zn(CN)(2), TMSCN, or K(4) [Fe(CN)(6)]. However, this approach often suffers from drawbacks, such as the formation of stoichiometric amounts of metal waste, the poisoning of the metal catalysts, or the generation of toxic HCN gas. As a result, a range of "nonmetallic" organic cyano-group sources have been explored for the cyanation of aryl halides and arene C-H bonds. This Minireview summarizes types of nonmetallic cyano-group sources and their applications in the preparation of aryl nitriles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A study on non-metallic structure of heliostat

    Energy Technology Data Exchange (ETDEWEB)

    Liu Xiaobin; Zang Chuncheng; Zhang Xiliang; Wang Yangzhong; Du Fengli [Himin Solar Energy Group Co., Ltd, Dezhou City (China); Wang Zhifeng [Inst. of Electrical Engineering, CAS, BJ (China)

    2008-07-01

    Heliostat constitutes a very important component in the solar power tower system. Its importance derives from three aspects: one is the large proportion in the total cost, accounting for about 50% of the whole, the other is its concentration efficiency and reflectivity heavily determining the power conversion from solar thermal energy to electrical energy, another is itself power consumption amount highly expressing failure or success of the power plant. Therefore, serious efforts and considerations from the structure, motion and control mode to material selection have to be given in the design and optimization of heliostat. In the present paper, the mechanical and aging performance of non-metallic materials is investigated and compared. The possibility of these non-metallic materials in the application of heliostat structure is discussed. (orig.)

  3. COMPUTATIONAL FLUID DYNAMICS APPLIED TO THE STUDY OF INCLUSIONS FLOTATION IN STEELS FOR AUTOMOTIVE INDUSTRY

    Directory of Open Access Journals (Sweden)

    Ângelo Máximo Fernandes Marins

    2013-03-01

    Full Text Available The practice of inert gas bubbling in steel refining ladle aims the removal of non-metallic inclusions, in addition to thermal and compositional homogenization. Through physical and mathematical models of a secondary ladle refining, the effects of bubbling flow of inert gas and the number of porous plugs located at the bottom of the ladle are investigated. The velocity fields and flotation of non-metallic inclusions are analyzed by physical and mathematical modeling. The results are validated by analysis of images (PIV and the macroscopic model is compared by industrial results for inclusions analysis for steels used in the automotive sector

  4. Creep of timber joints

    NARCIS (Netherlands)

    Van de Kuilen, J.W.G.

    2008-01-01

    A creep analysis has been performed on nailed, toothed-plates and split-ring joints in a varying uncontrolled climate. The load levels varied between 30% and 50% of the average ultimate short term strength of these joints, tested in accordance with ISO 6891. The climate in which the tests were

  5. Creep Feeding Beef Calves

    OpenAIRE

    2005-01-01

    Creep feeding is the managerial practice of supplying supplemental feed (usually concentrates) to the nursing calf. Milk from a lactating beef cow furnishes only about 50 percent of the nutrients that a 3-4 month-old calf needs for maximum growth.

  6. Creep behaviour and creep mechanisms of normal and healing ligaments

    Science.gov (United States)

    Thornton, Gail Marilyn

    Patients with knee ligament injuries often undergo ligament reconstructions to restore joint stability and, potentially, abate osteoarthritis. Careful literature review suggests that in 10% to 40% of these patients the graft tissue "stretches out". Some graft elongation is likely due to creep (increased elongation of tissue under repeated or sustained load). Quantifying creep behaviour and identifying creep mechanisms in both normal and healing ligaments is important for finding clinically relevant means to prevent creep. Ligament creep was accurately predicted using a novel yet simple structural model that incorporated both collagen fibre recruitment and fibre creep. Using the inverse stress relaxation function to model fibre creep in conjunction with fibre recruitment produced a superior prediction of ligament creep than that obtained from the inverse stress relaxation function alone. This implied mechanistic role of fibre recruitment during creep was supported using a new approach to quantify crimp patterns at stresses in the toe region (increasing stiffness) and linear region (constant stiffness) of the stress-strain curve. Ligament creep was relatively insensitive to increases in stress in the toe region; however, creep strain increased significantly when tested at the linear region stress. Concomitantly, fibre recruitment was evident at the toe region stresses; however, recruitment was limited at the linear region stress. Elevating the water content of normal ligament using phosphate buffered saline increased the creep response. Therefore, both water content and fibre recruitment are important mechanistic factors involved in creep of normal ligaments. Ligament scars had inferior creep behaviour compared to normal ligaments even after 14 weeks. In addition to inferior collagen properties affecting fibre recruitment and increased water content, increased glycosaminoglycan content and flaws in scar tissue were implicated as potential mechanisms of scar creep

  7. Reassembling Surveillance Creep

    DEFF Research Database (Denmark)

    Bøge, Ask Risom; Lauritsen, Peter

    2017-01-01

    We live in societies in which surveillance technologies are constantly introduced, are transformed, and spread to new practices for new purposes. How and why does this happen? In other words, why does surveillance “creep”? This question has received little attention either in theoretical...... development or in empirical analyses. Accordingly, this article contributes to this special issue on the usefulness of Actor-Network Theory (ANT) by suggesting that ANT can advance our understanding of ‘surveillance creep’. Based on ANT’s model of translation and a historical study of the Danish DNA database......, we argue that surveillance creep involves reassembling the relations in surveillance networks between heterogeneous actors such as the watchers, the watched, laws, and technologies. Second, surveillance creeps only when these heterogeneous actors are adequately interested and aligned. However...

  8. Testing theOdour Quality of Non-Metallic Materials

    Directory of Open Access Journals (Sweden)

    AVIJIT SINGH GANGWAR

    2014-10-01

    Full Text Available This report has been compiled on the completion of 3 week summer training at ICAT. It discusses about a very necessary and least popular part of the Automotive Industry i.e. Testing and Certification. It discusses about one of the government notified Testing body ICAT which is one of just 6 such organisations in India.This report deals with the odour quality testing of non-metallic materials that are used for automobile compartment and parts associated with the compartment.

  9. Creep failure of a spray drier

    CSIR Research Space (South Africa)

    Carter, P

    1998-06-01

    Full Text Available , and creep. The calculations pointed to creep, and no positive metallurgic or physical evidence was discovered to support any of the hypotheses. However, the compression stresses implied that creep deformation could have occurred without inducing discernible...

  10. Economic impact of using nonmetallic materials in low to intermediate temperature geothermal well construction

    Energy Technology Data Exchange (ETDEWEB)

    1979-12-01

    Four appendices are included. The first covers applications of low-temperature geothermal energy including industrial processes, agricultural and related processes, district heating and cooling, and miscellaneous. The second discusses hydrogeologic factors affecting the design and construction of low-temperature geothermal wells: water quality, withdrawal rate, water depth, water temperature, basic well designs, and hydrogeologic provinces. In the third appendix, properties of metallic and nonmetallic materials are described, including: specific gravity, mechanical strength properties, resistance to physical and biological attack, thermal properties of nonmetallics, fluid flow characteristics, corrosion resistance, scaling resistance, weathering resistance of nonmetallics, and hydrolysis resistance of nonmetallics. Finally, special considerations in the design and construction of low-temperature geothermal wells using nonmetallics materials are covered. These include; drilling methods, joining methods, methods of casing and screen installation, well cementing, and well development. (MHR)

  11. Creep buckling analysis of shells

    Energy Technology Data Exchange (ETDEWEB)

    Stone, C.M.; Nickell, R.E.

    1977-01-01

    The current study was conducted in an effort to determine the degree of conservatism or lack of conservatism in current ASME design rules concerning time-dependent (creep) buckling. In the course of this investigation, certain observations were made concerning the numerical solution of creep buckling problems. It was demonstrated that a nonlinear finite element code could be used to solve the time-dependent buckling problem. A direct method of solution was presented which proved to be computationally efficient and provided answers which agreed very well with available analytical solutions. It was observed that the calculated buckling times could vary widely for small errors in computed displacements. The presence of high creep strain rates contributed to the prediction of early buckling times when calculated during the primary creep stage. The predicted time estimates were found to increase with time until the secondary stage was reached and the estimates approached the critical times predicted without primary creep. It can be concluded, therefore, that for most nuclear piping components, whose primary creep stage is small compared to the secondary stage, the effect of primary creep is negligible and can be omitted from the calculations. In an evaluation of the past and current ASME design rules for time-dependent, load controlled buckling, it was concluded that current use of design load safety factors is not equivalent to a safety factor of ten on service life for low creep exponents.

  12. Preconsolidation Pressure and Creep Settlements

    DEFF Research Database (Denmark)

    Thorsen, Grete

    1995-01-01

    of oedometer tests with undisturbed samples have been analysed by means of different methods to determine the pre-consolidation pressure. An attempt is made to estimate the creep rates on the basis of AMS 14C-datings of the sediments and a model for creep determination proposed by Moust Jacobsen....

  13. Rationalization of Creep Data of Creep-Resistant Steels on the Basis of the New Power Law Creep Equation

    Science.gov (United States)

    Wang, Q.; Yang, M.; Song, X. L.; Jia, J.; Xiang, Z. D.

    2016-07-01

    The conventional power law creep equation (Norton equation) relating the minimum creep rate to creep stress and temperature cannot be used to predict the long-term creep strengths of creep-resistant steels if its parameters are determined only from short-term measurements. This is because the stress exponent and activation energy of creep determined on the basis of this equation depend on creep temperature and stress and these dependences cannot be predicted using this equation. In this work, it is shown that these problems associated with the conventional power law creep equation can be resolved if the new power law equation is used to rationalize the creep data. The new power law creep equation takes a form similar to the conventional power law creep equation but has a radically different capability not only in rationalizing creep data but also in predicting the long-term creep strengths from short-term test data. These capabilities of the new power law creep equation are demonstrated using the tensile strength and creep test data measured for both pipe and tube grades of the creep-resistant steel 9Cr-1.8W-0.5Mo-V-Nb-B (P92 and T92).

  14. Standard practice for process compensated resonance testing via swept sine input for metallic and Non-Metallic parts

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This practice describes a general procedure for using the process compensated resonance testing (PCRT) via swept sine input method to identify metallic and non-metallic parts’ resonant pattern differences that can be used to indentify parts with anomalies causing deficiencies in the expected performance of the part in service. This practice is intended for use with instruments capable of exciting, measuring, recording, and analyzing multiple whole body mechanical vibration resonant frequencies within parts exhibiting acoustical ringing in the audio, or ultrasonic, resonant frequency ranges, or both. PCRT is used in the presence of manufacturing process variance to distinguish acceptable parts from those containing significant anomalies in physical characteristics expected to significantly alter the performance. Such physical characteristics include, but are not limited to, cracks, voids, porosity, shrink, inclusions, discontinuities, grain and crystalline structure differences, density related anomalies...

  15. A RISK MANAGEMENT METHODOLOGY FOR NON-METALLIC PROCESS EQUIPMENT

    Directory of Open Access Journals (Sweden)

    J.J. Viviers

    2012-01-01

    Full Text Available

    ENGLISH ABSTRACT: Many companies in South Africa have implemented the risk-based inspection (RBI methodology as a maintenance strategy. The risk involved in operating a piece of equipment, past history, non-destructive examination techniques, failure modes, and many other aspects determine the frequency of inspections required to meet legislation. The main purpose of the RBI methodology is to prevent failures of process equipment. The methodology for risk-based inspection for metal equipment is well-established and has been proven in industry, becoming the norm nationally and internationally. However, it is not possible to apply all the techniques to nonmetallic equipment owing to vast differences between the two types of materials. This paper discusses the results of data gathered on the RBI methodology for nonmetallic equipment, and proposes a risk-based model that can be used to perform a risk assessment for non-metallic equipment in a process plant. The risk assessment can be used to formulate the next inspection interval for the asset.

    AFRIKAANSE OPSOMMING: Verskeie maatskappye in Suid-Afrika het reeds die metodologie van risikogebaseeerde inspeksie (RBI geïmplementeer as deel van ‘n omvattende instandhoudingstrategie. Die risiko betrokke by ‘n fisiese item, bedryfsgeskiedenis, nie-vernietigende toetstegnieke, falingsmodusse, en vele ander aspekte bepaal die frekwensie van inspeksies wat benodig word om aan wetlike vereistes te voldoen. Die hoofdoel van die risiko-gebaseerde metodologie is om faling van prosestoerusting te verhinder. Die metodologie vir risiko-gebaseerde inspeksie van metaaltoerusting is goed bekend en word suksesvol toegepas in die industrie. Dis is egter nie moontlik om al die tegnieke toe te pas op nie-metaaltoerusting nie weens die groot verskeidenheid van materiaaltipes. Hierdie artikel bespreek die data wat ingewin is op die risiko-gebaseerde metodologie vir nie-metaaltipeprosestoerusting, en stel

  16. Negative creep in nickel base superalloys

    DEFF Research Database (Denmark)

    Dahl, Kristian Vinter; Hald, John

    2004-01-01

    Negative creep describes the time dependent contraction of a material as opposed to the elongation seen for a material experiencing normal creep behavior. Negative creep occurs because of solid state transformations that results in lattice contractions. For most applications negative creep will h...

  17. Radiation damage in nonmetallic solids under dense electronic excitation

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Noriaki; Tanimura, Katsumi; Nakai, Yasuo (Dept. of Physics, Nagoya Univ. (Japan))

    1992-03-01

    Basic processes of radiation damage of insulators by dense electronic excitation are reviewed. First it is pointed out that electronic excitation of nonmetallic solids produces the self-trapped excitons and defect-related metastable states having relatively long lifetimes, and that the excitation of these metastable states, produces stable defects. The effects of irradiation with heavy ions, including track registration, are surveyed on the basis of the microscopic studies. It is pointed out also that the excitation of the metastable states plays a role in laser-induced damage at relatively low fluences, while the laser damage has been reported to be governed by heating of free electrons produced by multiphoton excitation. Difference in the contributions of the excitation of metastable defects to laser-induced damage of surfaces, or laser ablation, and laser-induced bulk damage is stressed. (orig.).

  18. Creep in electronic ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Routbort, J. L.; Goretta, K. C.; Arellano-Lopez, A. R.

    2000-04-27

    High-temperature creep measurements combined with microstructural investigations can be used to elucidate deformation mechanisms that can be related to the diffusion kinetics and defect chemistry of the minority species. This paper will review the theoretical basis for this correlation and illustrate it with examples from some important electronic ceramics having a perovskite structure. Recent results on BaTiO{sub 3}, (La{sub 1{minus}x}Sr){sub 1{minus}y}MnO{sub 3+{delta}}, YBa{sub 2}Cu{sub 3}O{sub x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Sr(Fe,Co){sub 1.5}O{sub x} will be presented.

  19. Numerical simulation of stress fi eld in inclusions of large rudder arm steel castings

    Directory of Open Access Journals (Sweden)

    Yang Dixin

    2009-08-01

    Full Text Available The infl uence of non-metallic inclusions on quality and performance of steel depends on not only the quantity of inclusions, but also the type, shape, size, distribution, and deformation behavior. In this paper, ANSYS fi nite element analysis software is used to simulate the stress fi eld of inclusions appearing in heavy rudder arm steel castings, the effects of inclusion type, shape, distribution, and various loading conditions were studied. The micromechanics of inclusions in such castings were also analyzed. Such research provides further clarifi cation on reaction mechanism of inclusions under complex loading conditions.

  20. Numerical simulation of stress field in inclusions of large rudder arm steel castings

    Institute of Scientific and Technical Information of China (English)

    Yang Dixin; Xie Jingpei; Zhang Kefeng; Liu Zongfa; Wang Aiqin; Wang Wenyan

    2009-01-01

    The influence of non-metallic inclusions on quality and performance of steel depends on not only the quantity of inclusions,but also the type,shape,size,distribution,and deformation behavior. In this paper,ANSYS finite element analysis software is used to simulate the stress field of inclusions appearing in heavy rudder arm steel castings,the effects of inclusion type,shape,distribution,and various loading conditions were studied. The micromechanics of inclusions in such castings were also analyzed. Such research provides further cladficetion on reaction mechanism of inclusions under complex loading conditions.

  1. Study of Inverse Creep In Textile Yarns

    Directory of Open Access Journals (Sweden)

    P.G. Patil

    2009-12-01

    Full Text Available Creep has been known and studied for textilematerials for decades. In comparison, a newlyobserved phenomenon of inverse creep seems not tohave received much attention. A new instrument hasbeen fabricated to measure creep and inverse creep intextile materials particularly yarns. Creep and Inversecreep measurements of nylon multifilament yarn,polyester multifilament yarn, cotton and wool yarn atdifferent levels of stress have been studied using thenew instrument and results are reported in the presentpaper.

  2. Creep modelling of particle strengthened steels

    OpenAIRE

    Magnusson, Hans

    2010-01-01

    Materials used in thermal power plants have to resist creep deformation for time periods up to 30 years. Material evaluation is typically based on creep testing with a maximum duration of a few years. This information is used as input when empirically deriving models for creep. These kinds of models are of limited use when considering service conditions or compositions different from those in the experiments. In order to provide a more general model for creep, the mechanisms that give creep s...

  3. Interaction of Non-Metallic Inclusion Particles with Advancing Solidification Front

    Directory of Open Access Journals (Sweden)

    Kalisz D.

    2014-06-01

    Full Text Available Praca zajmuje się zjawiskiem oddziały wania przemieszczającego frontu krystalizacji na cząstki wydzieleń niemetalicznych. Analizowano zachowanie pojedynczej cząstki wydzielenia w pobliżu poziomego i pionowego frontu. Scharakteryzowano siły działające na cząstkę w pobliżu frontu i sformułowano warunek równowagi, z którego wynika szybkość krytyczna frontu. Wyniki obliczeń zilustrowano w postaci wykresów.

  4. Plasticity and creep of metals

    CERN Document Server

    Rusinko, Andrew

    2011-01-01

    Here is a systematic presentation of the postulates, theorems and principles of mathematical theories of plasticity and creep in metals, and their applications. Special attention is paid to analysis of the advantages and shortcomings of the classical theories.

  5. null Seismic Creep, null Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden rupture associated with an earthquake. It is a usually slow deformation...

  6. The Inclusive Classroom: How Inclusive Is Inclusion?

    Science.gov (United States)

    Reid, Claudette M.

    2010-01-01

    This paper presents the position that inclusion is limited; inclusion does not go far enough. The inclusive classroom has been assessed to be of benefit both to the teacher and student. There are, however, limits set on inclusion. In most classrooms only children with learning disability are included omitting those with severe disabilities,…

  7. Methodology of inclusions removing from steel flowing through the tundish

    Directory of Open Access Journals (Sweden)

    M. Warzecha

    2017-01-01

    Full Text Available Obtaining high quality steels mainly depends on the quantity of non-metallic inclusions contained into it and this, in turn, to a large extent on the structure of the flow in the tundish. Optimization of the flow of liquid steel through the tundish makes it possible to control the trajectory of inclusions and thereby to improve the conditions of their outflow into the slag layer. The following article presents an analysis of research opportunities of the inclusions distribution and removing process from the steel flowing through the tundish, resulting in reconstruction of the own research facility.

  8. Encapsulation of nonmetallic fractions recovered from printed circuit boards waste with thermoplastic.

    Science.gov (United States)

    Muniyandi, Shantha Kumari; Sohaili, Johan; Hassan, Azman

    2014-09-01

    The present work includes a process for encapsulation by combining substantially simultaneously dry nonmetallic printed circuit boards (PCBs) powder and recycled high-density polyethylene (rHDPE) in an extruder to form a homogenous matrix. The extruded materials were then molded into standard tensile, flexural, and impact properties testing specimens. Nonmetallic PCB mainly consists of large amount of glass fiber-reinforced epoxy resin materials. Incorporation of 50 wt% nonmetallic PCB in rHDPE matrix had increased the flexural strength and modulus by 35% and 130%, respectively. Tensile strength reported to be constant without much improvement. However, the Young's modulus has increased by 180%, with incorporation of 50 wt% nonmetallic PCB. The addition of 6 phr (parts per hundred) maleated polyethylene (MAPE) resulted in 2-fold increase in tensile and flexural strength. Regarding the leaching properties, Cu was identified as the metal that leached at the highest level from the raw nonmetallic PCB, at 59.09 mg/L. However, after the nonmetallic PCB was filled in rHDPE/PCB composites, the concentration of Cu was reduced far below the regulatory limit, to only 3 mg/L. Thermal properties of composites were studied, and it was found out that incorporation of nonmetallic PCB fillers in rHDPE resulted in low thermal conductivity, whereas mechanical strength of the composites showed maximum improvements at 220 degrees C. Overall, the encapsulation technique using nonmetallic PCB waste has formed a monolithic waste form that provides a barrier to the dispersion of wastes into the environment. Implications: Nonmetallic materials reclaimed from waste PCBs were used to analyze the chemical composition, and it was found that nonmetalllic PCBs mainly consist of glass fiber-reinforced epoxy resin materials. With such millions of glass fibers in nonmetallic PCBs, there are mass-excellent supporting bodies that enhance the mechanical properties of composites. In fact, utilization

  9. Converting non-metallic printed circuit boards waste into a value added product

    OpenAIRE

    Shantha Kumari Muniyandi; Johan Sohaili; Azman Hassan; Siti Suhaila Mohamad

    2013-01-01

    The aim of this study was to investigate the feasibility of using nonmetallic printed circuit board (PCB) waste as filler in recycled HDPE (rHDPE) in production of rHDPE/PCB composites. Maleic anhydride modified linear low-density polyethylene (MAPE) was used as compatibilizer. In particular, the effects of nonmetallic PCB and MAPE on mechanical properties of the composites were assessed through tensile, flexural and impact testing. Scanning electron microscope (SEM) was used to study the dis...

  10. Contemporary overview of soil creep phenomenon

    Directory of Open Access Journals (Sweden)

    Kaczmarek Łukasz

    2017-06-01

    Full Text Available Soil creep deformation refers to phenomena which take place in many areas and research in this field of science is rich and constantly developing. The article presents an analysis of the literature on soil creep phenomena. In light of the complexity of the issues involved and the wide variety of perspectives taken, this attempt at systematization seeks to provide a reliable review of current theories and practical approaches concerning creep deformation. The paper deals with subjects such as definition of creep, creep genesis, basic description of soil creep dynamics deformation, estimation of creep capabilities, various fields of creep occurrence, and an introduction to creep modeling. Furthermore, based on this analysis, a new direction for research is proposed.

  11. 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.

  12. Contemporary overview of soil creep phenomenon

    Science.gov (United States)

    Kaczmarek, Łukasz; Dobak, Paweł

    2017-06-01

    Soil creep deformation refers to phenomena which take place in many areas and research in this field of science is rich and constantly developing. The article presents an analysis of the literature on soil creep phenomena. In light of the complexity of the issues involved and the wide variety of perspectives taken, this attempt at systematization seeks to provide a reliable review of current theories and practical approaches concerning creep deformation. The paper deals with subjects such as definition of creep, creep genesis, basic description of soil creep dynamics deformation, estimation of creep capabilities, various fields of creep occurrence, and an introduction to creep modeling. Furthermore, based on this analysis, a new direction for research is proposed.

  13. (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.

  14. Deterministic and Probabilistic Creep and Creep Rupture Enhancement to CARES/Creep: Multiaxial Creep Life Prediction of Ceramic Structures Using Continuum Damage Mechanics and the Finite Element Method

    Science.gov (United States)

    Jadaan, Osama M.; Powers, Lynn M.; Gyekenyesi, John P.

    1998-01-01

    High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep ripture criterion However, that model did not take into account the deteriorating state of the material due to creep damage (e.g., cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial creep curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of stress, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions This creep life prediction methodology was preliminarily added to the integrated design code CARES/Creep (Ceramics Analysis and Reliability Evaluation of Structures/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of this methodology and

  15. Interaction of silicene and germanene with non-metallic substrates

    Science.gov (United States)

    Houssa, M.; Scalise, E.; van den Broek, B.; Lu, A.; Pourtois, G.; Afanas'ev, V. V.; Stesmans, A.

    2015-01-01

    By using first-principles simulations, we investigate the interaction of silicene and germanene with various non-metallic substrates. We first consider weak van der Waals interactions between the 2D layers and dichalcogenide substrates, like MoX2 (X=S, Se, Te). The buckling of the silicene or germanene layer is correlated to the lattice mismatch between the 2D material and the MoX2 template. The electronic properties of silicene or germanene on these different templates then largely depend on the buckling of the 2D material layer: highly buckled silicene or germanene on MoS2 are predicted to be metallic, while low buckled silicene on MoTe2 is predicted to be semi-metallic, with preserved Dirac cones at the K points. We next study the covalent bonding of silicene and germanene on (0001) ZnS and ZnSe surfaces. On these substrates, silicene or germanene are found to be semiconducting. Remarkably, the nature and magnitude of their energy band gap can be controlled by an out-of-plane electric field.

  16. Large earthquakes and creeping faults

    Science.gov (United States)

    Harris, Ruth A.

    2017-01-01

    Faults are ubiquitous throughout the Earth's crust. The majority are silent for decades to centuries, until they suddenly rupture and produce earthquakes. With a focus on shallow continental active-tectonic regions, this paper reviews a subset of faults that have a different behavior. These unusual faults slowly creep for long periods of time and produce many small earthquakes. The presence of fault creep and the related microseismicity helps illuminate faults that might not otherwise be located in fine detail, but there is also the question of how creeping faults contribute to seismic hazard. It appears that well-recorded creeping fault earthquakes of up to magnitude 6.6 that have occurred in shallow continental regions produce similar fault-surface rupture areas and similar peak ground shaking as their locked fault counterparts of the same earthquake magnitude. The behavior of much larger earthquakes on shallow creeping continental faults is less well known, because there is a dearth of comprehensive observations. Computational simulations provide an opportunity to fill the gaps in our understanding, particularly of the dynamic processes that occur during large earthquake rupture and arrest.

  17. Crack initiation and propagation induced by inclusions in a nickel-base P/M superalloy under fatigue load

    Institute of Scientific and Technical Information of China (English)

    ZENG Yanping; ZHANG Maicang; DONG Jianxin; ZHANG Lina; XIE Xishan

    2005-01-01

    In situ fatigue tests in special designed SEM were conducted to trace the whole process of crack initiation and propagation till to fracture in nickel-base P/M superalloy seeded inclusions. The experimental results show that non-metallic inclusions can induce crack initiation. When the inclusion size is larger than the critical one, the crack can propagate as the main crack that induces the specimen to fracture. As a result, the LCF life of the specimen decreases.

  18. Creep Behaviour of Modified Mar-247 Superalloy

    Directory of Open Access Journals (Sweden)

    Cieśla M.

    2016-06-01

    Full Text Available The paper presents the results of analysis of creep behaviour in short term creep tests of cast MAR-247 nickel-based superalloy samples made using various modification techniques and heat treatment. The accelerated creep tests were performed under temperature of 982 °C and the axial stresses of σ = 150 MPa (variant I and 200 MPa (variant II. The creep behaviour was analysed based on: creep durability (creep rupture life, steady-state creep rate and morphological parameters of macro- and microstructure. It was observed that the grain size determines the creep durability in case of test conditions used in variant I, durability of coarse-grained samples was significantly higher.

  19. Geometric Modeling of Inclusions as Ellipsoids

    Science.gov (United States)

    Bonacuse, Peter J.

    2008-01-01

    Nonmetallic inclusions in gas turbine disk alloys can have a significant detrimental impact on fatigue life. Because large inclusions that lead to anomalously low lives occur infrequently, probabilistic approaches can be utilized to avoid the excessively conservative assumption of lifing to a large inclusion in a high stress location. A prerequisite to modeling the impact of inclusions on the fatigue life distribution is a characterization of the inclusion occurrence rate and size distribution. To help facilitate this process, a geometric simulation of the inclusions was devised. To make the simulation problem tractable, the irregularly sized and shaped inclusions were modeled as arbitrarily oriented, three independent dimensioned, ellipsoids. Random orientation of the ellipsoid is accomplished through a series of three orthogonal rotations of axes. In this report, a set of mathematical models for the following parameters are described: the intercepted area of a randomly sectioned ellipsoid, the dimensions and orientation of the intercepted ellipse, the area of a randomly oriented sectioned ellipse, the depth and width of a randomly oriented sectioned ellipse, and the projected area of a randomly oriented ellipsoid. These parameters are necessary to determine an inclusion s potential to develop a propagating fatigue crack. Without these mathematical models, computationally expensive search algorithms would be required to compute these parameters.

  20. Thermal Creep Force: Analysis And Application

    Science.gov (United States)

    2016-06-01

    Calhoun: The NPS Institutional Archive Theses and Dissertations Thesis and Dissertation Collection 2016-06 Thermal creep force: analysis and...CALIFORNIA DISSERTATION Approved for public release; distribution is unlimited THERMAL CREEP FORCE: ANALYSIS AND APPLICATION by David...blank) 2. REPORT DATE June 2016 3. REPORT TYPE AND DATES COVERED Doctoral Dissertation 4. TITLE AND SUBTITLE THERMAL CREEP FORCE: ANALYSIS

  1. Microstructurally sensitive crack nucleation around inclusions in powder metallurgy nickel based superalloys

    OpenAIRE

    Jiang, J; Yang, J; Zhang, T.; J Zou; Wang,Y.,; Dunne, F.P.E.; Britton, T. B.

    2016-01-01

    ? 2016 Acta Materialia Inc.Nickel-based superalloys are used in high strength, high-value applications, such as gas turbine discs in aero engines. In these applications the integrity of the disc is critical and therefore understanding crack initiation mechanisms is of high importance. With an increasing trend towards powder metallurgy routes for discs, sometimes unwanted non-metallic inclusions are introduced during manufacture. These inclusions vary in size from ?10??m to 200??m which is com...

  2. Creep and Creep-Fatigue of Alloy 617 Weldments

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Jill K. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Carroll, Laura J. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wright, Richard N. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-08-01

    Alloy 617 is the primary candidate material for the heat exchanger of a very high temperature gas cooled reactor intended to operate up to 950°C. While this alloy is currently qualified in the ASME Boiler and Pressure Vessel Code for non-nuclear construction, it is not currently allowed for use in nuclear designs. A draft Code Case to qualify Alloy 617 for nuclear pressure boundary applications was submitted in 1992, but was withdrawn prior to approval. Prior to withdrawal of the draft, comments were received indicating that there was insufficient knowledge of the creep and creep-fatigue behavior of Alloy 617 welds. In this report the results of recent experiments and analysis of the creep-rupture behavior of Alloy 617 welds prepared using the gas tungsten arc process with Alloy 617 filler wire. Low cycle fatigue and creep-fatigue properties of weldments are also discussed. The experiments cover a range of temperatures from 750 to 1000°C to support development of a new Code Case to qualify the material for elevated temperature nuclear design. Properties of the welded material are compared to results of extensive characterization of solution annealed plate base metal.

  3. Converting non-metallic printed circuit boards waste into a value added product.

    Science.gov (United States)

    Muniyandi, Shantha Kumari; Sohaili, Johan; Hassan, Azman; Mohamad, Siti Suhaila

    2013-01-01

    The aim of this study was to investigate the feasibility of using nonmetallic printed circuit board (PCB) waste as filler in recycled HDPE (rHDPE) in production of rHDPE/PCB composites. Maleic anhydride modified linear low-density polyethylene (MAPE) was used as compatibilizer. In particular, the effects of nonmetallic PCB and MAPE on mechanical properties of the composites were assessed through tensile, flexural and impact testing. Scanning electron microscope (SEM) was used to study the dispersion of nonmetallic PCB and MAPE in the matrix. Nonmetallic PCB was blended with rHDPE from 0-30 wt% and prepared by counter-rotating twin screw extruder followed by molding into test samples via hot press for analysis. A good balance between stiffness, strength and toughness was achieved for the system containing 30 wt% PCB. Thus, this system was chosen in order to investigate the effect of the compatibilizer on the mechanical properties of the composites. The results indicate that MAPE as a compatiblizer can effectively promote the interfacial adhesion between nonmetallic PCB and rHDPE. The addition of 6 phr MAPE increased the flexural strength, tensile strength and impact strength by 71%, 98% and 44% respectively compared to the uncompatibilized composites.

  4. Converting Non-Metallic Printed Circuit Boards Waste Into A Value Added Product

    Directory of Open Access Journals (Sweden)

    Shantha Kumari Muniyandi

    2013-05-01

    Full Text Available The aim of this study was to investigate the feasibility of using nonmetallic printed circuit board (PCB waste as filler in recycled HDPE (rHDPE in production of rHDPE/PCB composites. Maleic anhydride modified linear low-density polyethylene (MAPE was used as compatibilizer. In particular, the effects of nonmetallic PCB and MAPE on mechanical properties of the composites were assessed through tensile, flexural and impact testing. Scanning electron microscope (SEM was used to study the dispersion of nonmetallic PCB and MAPE in the matrix. Nonmetallic PCB was blended with rHDPE from 0--30 wt% and prepared by counter-rotating twin screw extruder followed by molding into test samples via hot press for analysis. A good balance between stiffness, strength and toughness was achieved for the system containing 30 wt% PCB. Thus, this system was chosen in order to investigate the effect of the compatibilizer on the mechanical properties of the composites. The results indicate that MAPE as a compatiblizer can effectively promote the interfacial adhesion between nonmetallic PCB and rHDPE. The addition of 6 phr MAPE increased the flexural strength, tensile strength and impact strength by 71%, 98% and 44% respectively compared to the uncompatibilized composites.

  5. X-ray detection of ingested non-metallic foreign bodies.

    Science.gov (United States)

    Saps, Miguel; Rosen, John M; Ecanow, Jacob

    2014-05-08

    To determine the utility of X-ray in identifying non-metallic foreign body (FB) and assess inter-radiologist agreement in identifying non-metal FB. Focus groups of nurses, fellows, and attending physicians were conducted to determine commonly ingested objects suitable for inclusion. Twelve potentially ingested objects (clay, plastic bead, crayon, plastic ring, plastic army figure, glass bead, paperclip, drywall anchor, eraser, Lego™, plastic triangle toy, and barrette) were embedded in a gelatin slab placed on top of a water-equivalent phantom to simulate density of a child's abdomen. The items were selected due to wide availability and appropriate size for accidental pediatric ingestion. Plain radiography of the embedded FBs was obtained. Five experienced radiologists blinded to number and types of objects were asked to identify the FBs. The radiologist was first asked to count the number of items that were visible then to identify the shape of each item and describe it to a study investigator who recorded all responses. Overall inter-rater reliability was analyzed using percent agreement and κ coefficient. We calculated P value to assess the probability of error involved in accepting the κ value. Fourteen objects were radiographed including 12 original objects and 2 duplicates. The model's validity was supported by clear identification of a radiolucent paperclip as a positive control, and lack of identification of plastic beads (negative control) despite repeated inclusion. Each radiologist identified 7-9 of the 14 objects (mean 8, 67%). Six unique objects (50%) were identified by all radiologists and four unique objects (33%) were not identified by any radiologist (plastic bead, Lego™, plastic triangle toy, and barrette). Identification of objects that were not present, false-positives, occurred 1-2 times per radiologist (mean 1.4). An additional 17% of unique objects were identified by less than half of the radiologists. Agreement between radiologists was

  6. Creep Resistance of VM12 Steel

    Directory of Open Access Journals (Sweden)

    Zieliński A.

    2016-09-01

    Full Text Available This article presents selected material characteristics of VM12 steel used for elements of boilers with super- and ultra-critical steam parameters. In particular, abridged and long-term creep tests with and without elongation measurement during testing and investigations of microstructural changes due to long-term impact of temperature and stress were carried out. The practical aspect of the use of creep test results in forecasting the durability of materials operating under creep conditions was presented. The characteristics of steels with regard to creep tests developed in this paper are used in assessment of changes in functional properties of the material of elements operating under creep conditions.

  7. Creep rupture of fiber bundles

    DEFF Research Database (Denmark)

    Linga, G.; Ballone, P.; Hansen, Alex

    2015-01-01

    The creep deformation and eventual breaking of polymeric samples under a constant tensile load F is investigated by molecular dynamics based on a particle representation of the fiber bundle model. The results of the virtual testing of fibrous samples consisting of 40000 particles arranged on Nc=4...

  8. Vegetative tillering in creeping bentgrass

    NARCIS (Netherlands)

    Cattani, D.J.

    2000-01-01

    Growth and development of creeping bentgrass ( Agrostis stolonifera L.) under non-competitive and competitive conditions were studied.Growth chamber experiments under non-competitive conditions with high and low tiller producing bentgrass populations produced plants with differing tiller appearance

  9. Vegetative tillering in creeping bentgrass

    NARCIS (Netherlands)

    Cattani, D.J.

    2000-01-01

    Growth and development of creeping bentgrass ( Agrostis stolonifera L.) under non-competitive and competitive conditions were studied.

    Growth chamber experiments under non-competitive conditions with high and low tiller producing bentgrass populations

  10. Creep at very low rates

    CSIR Research Space (South Africa)

    Nabarro, FRN

    2002-02-01

    Full Text Available The creep rate in a land-based power station must be less than 10(-11) s(-1). At these low rates of deformation the transport of matter occurs by the migration of vacancies rather than by the glide of dislocations. A quantitative understanding...

  11. Impression creep technique-An overview

    Energy Technology Data Exchange (ETDEWEB)

    Sastry, D.H. [Department of Metallurgy, Indian Institute of Science, Bangalore (India)]. E-mail: dhsastry@hotmail.com

    2005-11-15

    Impression creep technique is a modified indentation creep test wherein the conical or ball indenter is replaced by a cylindrical, flat bottomed punch. The usefulness of this technique, pioneered by Prof. Li, is illustrated by application to a variety of problems in this laboratory. High temperature creep behavior of a number of metals and alloys, particularly estimation of the thermal activation parameters aiding the identification of the rate controlling mechanisms of creep, has been investigated. The technique has also been exploited to assess the 'single crystal' creep behavior vis a vis that of a polycrystalline sample. Utilizing the impression creep test, the creep behavior of individual zones in steel weldments has been examined. The simplicity and the utility of the impression creep test have been further demonstrated by its application to the study of superplastic behavior in alloys. This paper presents a cross section of the results obtained in the above investigations. It is concluded that the impression creep test technique is capable of yielding much of the information that can be obtained from tensile creep testing. Furthermore, it can provide data which are either impossible or extremely difficult to obtain with conventional creep testing.

  12. Analysis of carbides and inclusions in high speed tool steels

    DEFF Research Database (Denmark)

    Therkildsen, K.T.; Dahl, K.V.

    2002-01-01

    The fracture surfaces of fatigued specimens were investigated using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). The aim was to quantify the distribution of cracked carbides and non-metallic inclusions on the fracturesurfaces as well as on polished cross......-metallic inclusions and the crack initiation. Surprisingly, no differences were found between the carbide size distributions of the micro-clean and conventional grades.Also, the distribution of the fractured carbides was found to be the same regardless of steel type, manufacturing method or location on the specimen....

  13. Modelling of non-metallic particles motion process in foundry alloys

    Directory of Open Access Journals (Sweden)

    P. L. Żak

    2015-04-01

    Full Text Available The behaviour of non-metallic particles in the selected composites was analysed, in the current study. The calculations of particles floating in liquids differing in viscosity were performed. Simulations based on the Stokes equation were made for spherical SiC particles and additionally the particle size influence on Reynolds number was analysed.The movement of the particles in the liquid metal matrix is strictly connected with the agglomerate formation problem.Some of collisions between non-metallic particles lead to a permanent connection between them. Creation of the two spherical particles and a metallic phase system generates the adhesion force. It was found that the adhesion force mainly depends on the surface tension of the liquid alloy and radius of non-metallic particles.

  14. Products Made from Nonmetallic Materials Reclaimed from Waste Printed Circuit Boards

    Institute of Scientific and Technical Information of China (English)

    MOU Peng; XIANG Dong; DUAN Guanghong

    2007-01-01

    Printed circuit boards (PCBs) are in all electronic equipment, so with the sharp increase of electronic waste, the recovery of PCB components has become a critical research field. This paper presents a study of the reclaimation and reuse of nonmetallic materials recovered from waste PCBs. Mechanical processes, such as crushing, milling, and separation, were used to process waste PCBs. Nonmetallic materials in the PCBs were separated using density-based separation with separation rates in excess of 95%. The recovered nonmetals were used to make models, construction materials, composite boards, sewer grates,and amusement park boats. The PCB nonmetal products have better mechanical characteristics and durability than traditional materials and fillers. The flexural strength of the PCB nonmetallic material composite boards is 30% greater than that of standard products. Products derived from PCB waste processing have been brought into industrial production. The study shows that PCB nonmetals can be reused in profitable and environmentally friendly ways.

  15. Building Inclusion

    NARCIS (Netherlands)

    Jeanet Kullberg; Isik Kulu-Glasgow

    2009-01-01

    The social inclusion of immigrants and ethnic minorities is a central issue in many European countries. Governments face challenges in ensuring housing for immigrants, delivering public services, promoting neighbourhood coexistence and addressing residential segregation. The Building Inclusion proje

  16. Mathematical modeling of fluid flow, heat transfer and inclusion transport in a four strand tundish

    Institute of Scientific and Technical Information of China (English)

    Yufeng Wang; Guanghua Wen; Ping Tang; Mingmei Zhu; Yuanqing Chen; Weizhao Song

    2007-01-01

    Mathematical simulation was used for trouble-shooting and optimization.By the mathematical simulation,fluid flow and heat transfer of molten-steel in a four-strand tundish of a billet caster under different conditions (bare tundish and tundish with flow control device) were analyzed.The results showed that (1) the tundish with flow control device (FCD) has an important effect on the fluid pattern and temperature distribution; (2) the unsteady solving method was used to model the inclusion motions at different time periods,and it showed that the FCD is advantageous to separate the nonmetallic inclusions.According to the simulation results,the main problem existing in the industry production was found,and some helpful measurements were executed.Consequently,the large nonmetallic inclusions were separated,and the content of total oxygen was reduced.The quality of steel was greatly improved.

  17. Quantitative characterization of mns inclusions in S355 steel regarding to solidification rate

    Directory of Open Access Journals (Sweden)

    Mahmutović Aida

    2013-01-01

    Full Text Available A practice of special interest for metallurgical steelmaking is the relationship between redistribution of solute elements and dendrite microsegregation that occurs during solidification. These phenomena have a significant impact on the final properties of cast and forged products. In this paper, a calculation of the characteristic chemical phases in S355 steel using a software program Thermo-Calc is presented. Also, the paper presents experimental measurements of the dendrites size and non-metallic inclusions using optical and electron probe microanalyzer, as well as the calculation of the local solidification rate on the particular example. These phenomena are of special interest when it comes to thin castings and higher cooling rates. Thin castings require higher quality of casting surface, corresponding distribution, and character than those of non-metallic inclusions. Thermo-calc software was used for calculation of equilibrium phases, temperature ranges of solidification of tested material, and temperature range for developing characteristic equilibrium phase. It was found that during solidification and cooling processes manganese sulphide inclusions were formed. Additionally, accurate values for solidus and liquidus temperatures, which coincide with the values of solidus and liquidus temperatures obtained by the Thermo Calc, were calculated. Using optical and electron probe microanalyzer, the type of inclusions were confirmed, whereas chemical composition and size measurement of dendrites, and formed non-metallic inclusions were determined. Mapping and Linescan methods were used to examine the size and exact chemical composition of sulphides in atomic percents. Using secondary dendrites local solidification rate was calculated (for casting surface area solidification rate was 5 K/s. This paper gives contribution to better understanding the influence of cooling rate on casting microstructure formation and dendrites, which essentially

  18. Creep-Fatigue Failure Diagnosis

    Directory of Open Access Journals (Sweden)

    Stuart Holdsworth

    2015-11-01

    Full Text Available Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of loading conditions ranging from pure cyclic to mainly steady loading with infrequent off-load transients. These require a range of mechanical analysis approaches, a number of which are reviewed. The microstructural information revealing material condition can vary with alloy class. In practice, the detail of the consequent cracking mechanism(s can be camouflaged by oxidation at high temperatures, although the presence of oxide on fracture surfaces can be used to date events leading to failure. Routine laboratory specimen post-test examination is strongly recommended to characterise the detail of deformation and damage accumulation under known and well-controlled loading conditions to improve the effectiveness and efficiency of failure diagnosis.

  19. Creep of Structural Nuclear Composites

    Energy Technology Data Exchange (ETDEWEB)

    Will Windes; R.W. Lloyd

    2005-09-01

    A research program has been established to investigate fiber reinforced ceramic composites to be used as control rod components within a Very High Temperature Reactor (VHTR) design. Two candidate systems have been identified, carbon fiber reinforced carbon (Cf/C) and silicon carbide fiber reinforced silicon carbide (SiCf/SiC) composites. One of the primary degradation mechanisms anticipated for these core components is high temperature thermal and irradiation enhanced creep. As a consequence, high temperature test equipment, testing methodologies, and test samples for very high temperature (up to 1600º C) tensile strength and long duration creep studies have been established. Actual testing of both tubular and flat, "dog-bone"-shaped tensile composite specimens will begin next year. Since there is no precedence for using ceramic composites within a nuclear reactor, ASTM standard test procedures are currently being established from these high temperature mechanical tests.

  20. High-pressure creep tests

    Science.gov (United States)

    Bhattacharyya, S.; Lamoureux, J.; Hales, C.

    1986-01-01

    The automotive Stirling engine, presently being developed by the U.S. Department of Energy and NASA, uses high-pressure hydrogen as a working fluid; its long-term effects on the properties of alloys are relatively unknown. Hence, creep-rupture testing of wrought and cast high-temperature alloys in high-pressure hydrogen is an essential part of the research supporting the development of the Stirling cycle engine. Attention is given to the design, development, and operation of a 20 MPa hydrogen high-temperature multispecimen creep-rupture possessing high sensitivity. This pressure vessel allows for the simultaneous yet independent testing of six specimens. The results from one alloy, XF-818, are presented to illustrate how reported results are derived from the raw test data.

  1. Creep of quartz by dislocation and grain boundary processes

    Science.gov (United States)

    Fukuda, J. I.; Holyoke, C. W., III; Kronenberg, A. K.

    2015-12-01

    Wet polycrystalline quartz aggregates deformed at temperatures T of 600°-900°C and strain rates of 10-4-10-6 s-1 at a confining pressure Pc of 1.5 GPa exhibit plasticity at low T, governed by dislocation glide and limited recovery, and grain size-sensitive creep at high T, governed by diffusion and sliding at grain boundaries. Quartz aggregates were HIP-synthesized, subjecting natural milky quartz powder to T=900°C and Pc=1.5 GPa, and grain sizes (2 to 25 mm) were varied by annealing at these conditions for up to 10 days. Infrared absorption spectra exhibit a broad OH band at 3400 cm-1 due to molecular water inclusions with a calculated OH content (~4000 ppm, H/106Si) that is unchanged by deformation. Rate-stepping experiments reveal different stress-strain rate functions at different temperatures and grain sizes, which correspond to differing stress-temperature sensitivities. At 600-700°C and grain sizes of 5-10 mm, flow law parameters compare favorably with those for basal plasticity and dislocation creep of wet quartzites (effective stress exponents n of 3 to 6 and activation enthalpy H* ~150 kJ/mol). Deformed samples show undulatory extinction, limited recrystallization, and c-axis maxima parallel to the shortening direction. Similarly fine-grained samples deformed at 800°-900°C exhibit flow parameters n=1.3-2.0 and H*=135-200 kJ/mol corresponding to grain size-sensitive Newtonian creep. Deformed samples show some undulatory extinction and grain sizes change by recrystallization; however, grain boundary deformation processes are indicated by the low value of n. Our experimental results for grain size-sensitive creep can be compared with models of grain boundary diffusion and grain boundary sliding using measured rates of silicon grain boundary diffusion. While many quartz mylonites show microstructural and textural evidence for dislocation creep, results for grain size-sensitive creep may apply to very fine-grained (<10 mm) quartz mylonites.

  2. Analysis of oxide inclusions in steel by fast laser-induced breakdown spectroscopy scanning: an approach to quantification.

    Science.gov (United States)

    Boué-Bigne, F

    2007-03-01

    Laser-induced breakdown spectroscopy (LIBS) measurements were performed on a steel sample to investigate the feasibility of obtaining fast information on cleanness. A calibration approach was considered to enable the quantification of the elemental composition of non-metallic inclusions; the same data was also used to estimate the size of the inclusions. For the first time, the quantified chemical composition data obtained by LIBS for non-metallic inclusions was compared to the corresponding results obtained from scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis, the conventional method used for steel cleanness assessment, and proved successful. Due to the speed of analysis and the systematic recording of the signal from the scanned area, LIBS enables the analysis of larger areas of sample and in significantly shorter time than with automated SEM-EDX. This paper summarizes the hitherto obtained results for the fast analysis of inclusions in steel by LIBS.

  3. Creep Strength of Discontinuous Fibre Composites

    DEFF Research Database (Denmark)

    Pedersen, Ole Bøcker

    1974-01-01

    relation between stress and strain rate. Expressions for the interface stress, the creep velocity profile adjacent to the fibres and the creep strength of the composite are derived. Previous results for the creep strength, sc = aVfs0 ( \\frac[( Î )\\dot] [( Î )\\dot] 0 )1/nr1 + 1/n c=Vf001n1+1n in which[( Î...... )\\dot] is the composite creep rate,V f is the fibre volume fraction,sgr 0,epsi 0 andn are the constants in the matrix creep law. The creep strength coefficient agr is found to be very weakly dependent onV f and practically independent ofn whenn is greater than about 6....

  4. Flexural creep behaviour of jute polypropylene composites

    Science.gov (United States)

    Chandekar, Harichandra; Chaudhari, Vikas

    2016-09-01

    Present study is about the flexural creep behaviour of jute fabric reinforced polypropylene (Jute-PP) composites. The PP sheet and alkali treated jute fabric is stacked alternately and hot pressed in compression molding machine to get Jute-PP composite laminate. The flexural creep study is carried out on dynamic mechanical analyzer. The creep behaviour of the composite is modeled using four-parameter Burgers model. Short-term accelerated creep testing is conducted which is later used to predict long term creep behaviour. The feasibility of the construction of a master curve using the time-temperature superposition (TTS) principle to predict long term creep behavior of unreinforced PP and Jute-PP composite is investigated.

  5. Creep of parylene-C film

    KAUST Repository

    Lin, Jeffrey Chun-Hui

    2011-06-01

    The glass transition temperature of as-deposited parylene-C is first measured to be 50°C with a ramping-temperature-dependent modulus experiment. The creep behavior of parylene-C film in the primary and secondary creep region is then investigated below and above this glass transition temperature using a dynamic mechanical analysis (DMA) machine Q800 from TA instruments at 8 different temperatures: 10, 25, 40, 60, 80, 100, 120 and 150°C. The Burger\\'s model, which is the combined Maxwell model and Kelvin-Voigt model, fits well with our primary and secondary creep data. Accordingly, the results show that there\\'s little or no creep below the glass transition temperature. Above the glass transition temperature, the primary creep and creep rate increases with the temperature, with a retardation time constant around 6 minutes. © 2011 IEEE.

  6. Room temperature creep in metals and alloys

    Energy Technology Data Exchange (ETDEWEB)

    Deibler, Lisa Anne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Materials Characterization and Performance

    2014-09-01

    Time dependent deformation in the form of creep and stress relaxation is not often considered a factor when designing structural alloy parts for use at room temperature. However, creep and stress relaxation do occur at room temperature (0.09-0.21 Tm for alloys in this report) in structural alloys. This report will summarize the available literature on room temperature creep, present creep data collected on various structural alloys, and finally compare the acquired data to equations used in the literature to model creep behavior. Based on evidence from the literature and fitting of various equations, the mechanism which causes room temperature creep is found to include dislocation generation as well as exhaustion.

  7. Creep rupture behavior of unidirectional advanced composites

    Science.gov (United States)

    Yeow, Y. T.

    1980-01-01

    A 'material modeling' methodology for predicting the creep rupture behavior of unidirectional advanced composites is proposed. In this approach the parameters (obtained from short-term tests) required to make the predictions are the three principal creep compliance master curves and their corresponding quasi-static strengths tested at room temperature (22 C). Using these parameters in conjunction with a failure criterion, creep rupture envelopes can be generated for any combination of in-plane loading conditions and ambient temperature. The analysis was validated experimentally for one composite system, the T300/934 graphite-epoxy system. This was done by performing short-term creep tests (to generate the principal creep compliance master curves with the time-temperature superposition principle) and relatively long-term creep rupture tensile tests of off-axis specimens at 180 C. Good to reasonable agreement between experimental and analytical results is observed.

  8. Stepped-Frequency Ground-Penetrating Radar for Detection of Small Non-metallic Buried Objects

    DEFF Research Database (Denmark)

    Jakobsen, Kaj Bjarne; Sørensen, Helge Bjarup Dissing; Nymann, Ole

    1997-01-01

    A monostatic amplitude and phase stepped-frequency radar approach have been proposed to detect small non-metallic buried anti-personnel (AP) mines. An M-56 AP-mine with a diameter of 54 mm and height of 40 mm, only, has been successfully detected and located in addition to small metallic mine...

  9. CHARACTERIZATION OF EMISSIONS FROM THE SIMULATED OPEN-BURNING OF NON-METALLIC AUTOMOBILE SHREDDER RESIDUE

    Science.gov (United States)

    The report gives results of a study in which the open combustion of a nonmetallic waste product called "fluff" was simulated and the resulting emissions collected and characterized to gain insight into the types and quantities of these air pollutants. (NOTE: The reclamation proce...

  10. Soil effects on GPR detection of buried non-metallic mines

    NARCIS (Netherlands)

    Hendrickx, J.M.H.; Hong, S.H.; Miller, T.; Borchers, B.; Rhebergen, J.B.

    2003-01-01

    Landmines are a major problem in many areas of the world. In spite of the fact that many different types of landmine sensors have been developed, the detection of non-metallic landmines remains very difficult. The objective of this contribution is to synthesize our work related to the effects of soi

  11. Economic impact of using nonmetallic materials in low to intermediate temperature geothermal well construction. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    1979-12-01

    The results are presented of an exhaustive literature search and evaluation concerning the properties and economics of commercially available nonmetallic well casing and screens. These materials were studied in terms of their use in low to intermediate temperature geothermal well construction.

  12. Creep Rupture Life Prediction Based on Analysis of Large Creep Deformation

    OpenAIRE

    YE Wenming; HU Xuteng; Ma, Xiaojian; SONG Yingdong

    2016-01-01

    A creep rupture life prediction method for high temperature component was proposed. The method was based on a true stress-strain elastoplastic creep constitutive model and the large deformation finite element analysis method. This method firstly used the high-temperature tensile stress-strain curve expressed by true stress and strain and the creep curve to build materials' elastoplastic and creep constitutive model respectively, then used the large deformation finite element method to calcula...

  13. A Creep Model for High Density Snow

    Science.gov (United States)

    2017-04-01

    Director of ERDC-CRREL was Dr. Lance Hansen, and the Director was Dr. Robert E. Davis. COL Bryan S. Green was Commander of ERDC, and Dr. David W...Station, Green - land, and that will be founded on a compacted snow surface. The defor- mation of snow under a constant load (creep deformation, or...developed in this study are enough similar to the generalized creep model used in the ABAQUS finite element software that the ABAQUS creep model was used

  14. Analogy betwen dislocation creep and relativistic cosmology

    OpenAIRE

    J.A. Montemayor-Aldrete; J.D. Muñoz-Andrade; Mendoza-Allende, A.; Montemayor-Varela, A.

    2005-01-01

    A formal, physical analogy between plastic deformation, mainly dislocation creep, and Relativistic Cosmology is presented. The physical analogy between eight expressions for dislocation creep and Relativistic Cosmology have been obtained. By comparing the mathematical expressions and by using a physical analysis, two new equations have been obtained for dislocation creep. Also, four new expressions have been obtained for Relativistic Cosmology. From these four new equations, one may determine...

  15. Engineering tools for robust creep modelling

    OpenAIRE

    Holmström, Stefan

    2010-01-01

    High temperature creep is often dealt with simplified models to assess and predict the future behavior of materials and components. Also, for most applications the creep properties of interest require costly long-term testing that limits the available data to support design and life assessment. Such test data sets are even smaller for welded joints that are often the weakest links of structures. It is of considerable interest to be able to reliably predict and extrapolate long term creep beha...

  16. Creep Resistance of VM12 Steel

    OpenAIRE

    Zieliński A.; Golański G.; Dobrzański J.; Sroka M.

    2016-01-01

    This article presents selected material characteristics of VM12 steel used for elements of boilers with super- and ultra-critical steam parameters. In particular, abridged and long-term creep tests with and without elongation measurement during testing and investigations of microstructural changes due to long-term impact of temperature and stress were carried out. The practical aspect of the use of creep test results in forecasting the durability of materials operating under creep conditions ...

  17. Creep Behavior of Passive Bovine Extraocular Muscle

    OpenAIRE

    Lawrence Yoo; Hansang Kim; Andrew Shin; Vijay Gupta; Demer, Joseph L.

    2011-01-01

    This paper characterized bovine extraocular muscles (EOMs) using creep, which represents long-term stretching induced by a constant force. After preliminary optimization of testing conditions, 20 fresh EOM samples were subjected to four different loading rates of 1.67, 3.33, 8.33, and 16.67%/s, after which creep was observed for 1,500 s. A published quasilinear viscoelastic (QLV) relaxation function was transformed to a creep function that was compared with data. Repeatable creep was observed...

  18. Creep characterization of solder bumps using nanoindentation

    Science.gov (United States)

    Du, Yingjie; Liu, Xiao Hu; Fu, Boshen; Shaw, Thomas M.; Lu, Minhua; Wassick, Thomas A.; Bonilla, Griselda; Lu, Hongbing

    2017-08-01

    Current nanoindentation techniques for the measurement of creep properties are applicable to viscoplastic materials with negligible elastic deformations. A new technique for characterization of creep behavior is needed for situations where the elastic deformation plays a significant role. In this paper, the effect of elastic deformation on the determination of creep parameters using nanoindentation with a self-similar nanoindenter tip is evaluated using finite element analysis (FEA). It is found that the creep exponent measured from nanoindentation without taking into account of the contribution of elastic deformation tends to be higher than the actual value. An effective correction method is developed to consider the elastic deformation in the calculation of creep parameters. FEA shows that this method provides accurate creep exponent. The creep parameters, namely the creep exponent and activation energy, were measured for three types of reflowed solder bumps using the nanoindentation method. The measured parameters were verified using FEA. The results show that the new correction approach allows extraction of creep parameters with precision from nanoindentation data.

  19. CREEP AND CREEP-FATIGUE OF ALLOY 617 WELDMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Jill; Carroll, Laura; Wright, Richard

    2014-08-01

    The Very High Temperature Reactor (VHTR) Intermediate Heat Exchanger (IHX) may be joined to piping or other components by welding. Creep-fatigue deformation is expected to be a predominant failure mechanism of the IHX1 and thus weldments used in its fabrication will experience varying cyclic stresses interrupted by periods of elevated temperature deformation. These periods of elevated temperature deformation are greatly influenced by a materials’ creep behavior. The nickel-base solid solution strengthened alloy, Alloy 617, is the primary material candidate for a VHTR-type IHX, and it is expected that Alloy 617 filler metal will be used for welds. Alloy 617 is not yet been integrated into Section III of the Boiler and Pressure Vessel Code, however, nuclear component design with Alloy 617 requires ASME (American Society of Mechanical Engineers) Code qualification. The Code will dictate design for welded construction through significant performance reductions. Despite the similar compositions of the weldment and base material, significantly different microstructures and mechanical properties are inevitable. Experience of nickel alloy welds in structural applications suggests that most high temperature failures occur at the weldments or in the heat-affected zone. Reliably guarding against this type of failure is particularly challenging at high temperatures due to the variations in the inelastic response of the constituent parts of the weldment (i.e., weld metal, heat-affected zone, and base metal) [ref]. This work focuses on the creep-fatigue behavior of nickel-based weldments, a need noted during the development of the draft Alloy 617 ASME Code Case. An understanding of Alloy 617 weldments when subjected to this important deformation mode will enable determination of the appropriate design parameters associated with their use. Specifically, the three main areas emphasized are the performance reduction due to a weld discontinuity in terms of the reduced number of

  20. Creep Behavior and Microstructure Evolution of P92 Steel During Creep Test at 873 K

    Science.gov (United States)

    Zhang, Zuogui; Shi, Kexian; Wang, Yanfeng; Lin, Fusheng

    In this paper, the creep behavior of P92 steel has been analyzed by creep strain and creep rate variations after the creep tests were stopped at the steady-state creep stage. The microstructure evolution of the P92 steel at the steady-state stage during creep test at 873 K under different load stresses of 125-160 MPa were studied by using a scanning electron microscopy (SEM) and a transmission electron microscopy (TEM). The grain boundary characteristics in the P92 steels during creep test were investigated by an electron backscattered diffraction (EBSD) technique. Experimental results showed that with increasing load stresses from 125 MPa to 160 MPa, creep rates of the P92 steels increased in Norton's power law relation and creep times to the steady-state creep stage decreased. With decreasing load stresses and increasing creep times, martensite lath microstructure occurred recovery and the dislocation densities in ferritic matrix decreased. M23C6 particles located in prior austenite grain, sub-grain and lath boundaries showed slight coarsening. Some Laves phase particles precipitated in the grain boundaries for the P92 specimens after creep test under a load stress of 125 MPa. Comparing to as-tempered P92 steel, the volume fractions of LAGBs are lower and the volume fraction of HAGBs are higher with decreasing load stresses and increasing creep times. It is considered that understanding on creep behavior and microstructual evolution of the P92 steels during creep test will effectively support life design and assessment of the high temperature metal parts in fossil-fired power plant.

  1. DETERMINATION OF CREEP PROPERTIES OF THERMAL BARRIER COATING(TBC) SYSTEMS FROM THE INDENTATION CREEP TESTING WITH ROUND FLAT INDENTERS

    Institute of Scientific and Technical Information of China (English)

    B. Zhao; B.X. Xu; J. Liu; Z.F. Yue

    2004-01-01

    Indentation creep behavior with cylindrical flat indenters on the thermal barrier coating (TBC) was studied by finite element method (FEM). On the constant applied indentation creep stress, there is a steady creep rate for each case studied for different creep properties of the TBC system. The steady creep depth rate depends on the applied indentation creep stress and size of the indenters as well as the creep properties of the bond coat of the TBC and the substrate. The possibilities to determine the creep properties of a thermal barrier system from indention creep testing were discussed. As an example, with two different size indenters, the creep properties of bond coat of the TBC system can be derived by an inverse FEM method. This study not only provides a numerical method to obtain the creep properties of the TBC system, but also extends the application of indentation creep method with cylindrical flat indenters.

  2. Inclusive Schools.

    Science.gov (United States)

    Schrag, Judy; Burnette, Jane

    1994-01-01

    This review of five recent (1992 and 1993) books and journal articles is intended to illuminate characteristics of inclusive schools. The review defines inclusion as more than merely regular class placement for students with disabilities, to include a philosophy which celebrates diversity and the provision of a continuum of educational options.…

  3. Inclusive Education

    Science.gov (United States)

    Lambert, Lukischa

    2008-01-01

    The placement and education of students with disabilities in the general education classroom has generated a challenge and varied opinions for educators, families, and service providers. It is likely that with recent litigation and legislation which supports inclusion and increasing pressure from advocates of inclusion, the trend towards including…

  4. Social inclusion and inclusive education

    Directory of Open Access Journals (Sweden)

    Marsela Robo

    2014-07-01

    In line with global debate on social inclusion and exclusion, the author brings the way this debate has now pervaded both the official and development policy discourse in Albania.Social inclusion is considered as one of the priorities of the current government, with poverty reduction as its main focus, which will be ensured not only through economic development. In the end, the article focuses on the role of education as a very important and useful tool for ensuring social inclusion.Social inclusion through education, in particular through vocational education, considered by the author as the only way towards sustainable development of Albanian society.

  5. Making Ice Creep in the Classroom

    Science.gov (United States)

    Prior, David; Vaughan, Matthew; Banjan, Mathilde; Hamish Bowman, M.; Craw, Lisa; Tooley, Lauren; Wongpan, Pat

    2017-04-01

    Understanding the creep of ice has direct application to the role of ice sheet flow in sea level and climate change and to modelling of icy planets and satellites of the outer solar system. Additionally ice creep can be used as an analogue for the high temperature creep of rocks, most particularly quartzites. We adapted technologies developed for ice creep experiments in the research lab, to build some inexpensive ( EU200) rigs to conduct ice creep experiments in an undergraduate (200 and 300 level) class in rock deformation. The objective was to give the students an experience of laboratory rock deformation experiments so that they would understand better what controls the creep rate of ice and rocks. Students worked in eight groups of 5/6 students. Each group had one deformation rig and temperature control system. Each group conducted two experiments over a 2 week period. The results of all 16 experiments were then shared so that all students could analyse the mechanical data and generate a "flow law" for ice. Additionally thin sections were made of each deformed sample so that some microstructural analysis could be incorporated in the data analysis. Students were able to derive a flow law that showed the relationship of creep rate to both stress and temperature. The flow law matches with those from published research. The class did provide a realistic introduction to laboratory rock deformation experiments and helped students' understanding of what controls the creep of rocks.

  6. 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...

  7. Creep behavior of passive bovine extraocular muscle.

    Science.gov (United States)

    Yoo, Lawrence; Kim, Hansang; Shin, Andrew; Gupta, Vijay; Demer, Joseph L

    2011-01-01

    This paper characterized bovine extraocular muscles (EOMs) using creep, which represents long-term stretching induced by a constant force. After preliminary optimization of testing conditions, 20 fresh EOM samples were subjected to four different loading rates of 1.67, 3.33, 8.33, and 16.67%/s, after which creep was observed for 1,500 s. A published quasilinear viscoelastic (QLV) relaxation function was transformed to a creep function that was compared with data. Repeatable creep was observed for each loading rate and was similar among all six anatomical EOMs. The mean creep coefficient after 1,500 seconds for a wide range of initial loading rates was at 1.37 ± 0.03 (standard deviation, SD). The creep function derived from the relaxation-based QLV model agreed with observed creep to within 2.7% following 16.67%/s ramp loading. Measured creep agrees closely with a derived QLV model of EOM relaxation, validating a previous QLV model for characterization of EOM biomechanics.

  8. Creep Behavior of Passive Bovine Extraocular Muscle

    Directory of Open Access Journals (Sweden)

    Lawrence Yoo

    2011-01-01

    Full Text Available This paper characterized bovine extraocular muscles (EOMs using creep, which represents long-term stretching induced by a constant force. After preliminary optimization of testing conditions, 20 fresh EOM samples were subjected to four different loading rates of 1.67, 3.33, 8.33, and 16.67%/s, after which creep was observed for 1,500 s. A published quasilinear viscoelastic (QLV relaxation function was transformed to a creep function that was compared with data. Repeatable creep was observed for each loading rate and was similar among all six anatomical EOMs. The mean creep coefficient after 1,500 seconds for a wide range of initial loading rates was at 1.37±0.03 (standard deviation, SD. The creep function derived from the relaxation-based QLV model agreed with observed creep to within 2.7% following 16.67%/s ramp loading. Measured creep agrees closely with a derived QLV model of EOM relaxation, validating a previous QLV model for characterization of EOM biomechanics.

  9. Irradiation creep of vanadium-base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, H.; Billone, M.C.; Strain, R.V.; Smith, D.L. [Argonne National Lab., IL (United States); Matsui, H. [Tohoku Univ. (Japan)

    1998-03-01

    A study of irradiation creep in vanadium-base alloys is underway with experiments in the Advanced Test Reactor (ATR) and the High Flux Isotope Reactor (HFIR) in the United States. Test specimens are thin-wall sealed tubes with internal pressure loading. The results from the initial ATR irradiation at low temperature (200--300 C) to a neutron damage level of 4.7 dpa show creep rates ranging from {approx}0 to 1.2 {times} 10{sup {minus}5}/dpa/MPa for a 500-kg heat of V-4Cr-4Ti alloy. These rates were generally lower than reported from a previous experiment in BR-10. Because both the attained neutron damage levels and the creep strains were low in the present study, however, these creep rates should be regarded as only preliminary. Substantially more testing is required before a data base on irradiation creep of vanadium alloys can be developed and used with confidence.

  10. Creep resistant high temperature martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Hawk, Jeffrey A.; Jablonski, Paul D.; Cowen, Christopher J.

    2017-01-31

    The disclosure provides a creep resistant alloy having an overall composition comprised of iron, chromium, molybdenum, carbon, manganese, silicon, nickel, vanadium, niobium, nitrogen, tungsten, cobalt, tantalum, boron, copper, and potentially additional elements. In an embodiment, the creep resistant alloy has a molybdenum equivalent Mo(eq) from 1.475 to 1.700 wt. % and a quantity (C+N) from 0.145 to 0.205. The overall composition ameliorates sources of microstructural instability such as coarsening of M.sub.23C.sub.6carbides and MX precipitates, and mitigates or eliminates Laves and Z-phase formation. A creep resistant martensitic steel may be fabricated by preparing a melt comprised of the overall composition followed by at least austenizing and tempering. The creep resistant alloy exhibits improved high-temperature creep strength in the temperature environment of around 650.degree. C.

  11. Creep resistant high temperature martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Hawk, Jeffrey A.; Jablonski, Paul D.; Cowen, Christopher J.

    2015-11-13

    The disclosure provides a creep resistant alloy having an overall composition comprised of iron, chromium, molybdenum, carbon, manganese, silicon, nickel, vanadium, niobium, nitrogen, tungsten, cobalt, tantalum, boron, and potentially additional elements. In an embodiment, the creep resistant alloy has a molybdenum equivalent Mo(eq) from 1.475 to 1.700 wt. % and a quantity (C+N) from 0.145 to 0.205. The overall composition ameliorates sources of microstructural instability such as coarsening of M.sub.23C.sub.6 carbides and MX precipitates, and mitigates or eliminates Laves and Z-phase formation. A creep resistant martensitic steel may be fabricated by preparing a melt comprised of the overall composition followed by at least austenizing and tempering. The creep resistant alloy exhibits improved high-temperature creep strength in the temperature environment of around 650.degree. C.

  12. Non-metallic, non-Fermi-liquid resistivity of FeCrAs from 0 to 17 GPa.

    Science.gov (United States)

    Tafti, F F; Wu, W; Julian, S R

    2013-09-25

    An unusual, non-metallic resistivity of the 111 iron-pnictide compound FeCrAs is shown to be relatively unchanged under pressures of up to 17 GPa. Combined with our previous finding that this non-metallic behaviour persists from at least 80 mK to 800 K, this shows that the non-metallic phase is exceptionally robust. Antiferromagnetic order, with a Néel temperature TN ∼ 125 K at ambient pressure, is suppressed by pressure at a rate of 7.0 ± 0.4 K GPa(-1), falling to ∼50 K at 10 GPa. We conclude that the formation of a spin-density-wave gap at TN does not play an important role in the non-metallic resistivity of FeCrAs at low temperatures.

  13. Creep behavior of Zr-Nb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Yong Chan; Kim, Young Suk; Cheong, Yong Mu; Kwon, Sang Chul; Kim, Sung Soo; Choo, Ki Nam [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2000-01-01

    The creep characteristics of Zirconium alloy is affected by several parameters. Out-reactor creep increases both with an increasing amount of Nb, Sn and S contained in alpha-Zr and decreases with the increasing volume of alpha-Zr. Especially, the creep of Zr-2.5Nb alloy depends on the solubility of Nb in alpha-Zr, which is associated with the decomposition of beta-Zr. Since Zr of the hcp structure is strongly anisotropic, it shows the characteristics of texture and results in the anisotropy of creep. Due to the circumferential texture of Zr-2.5%Nb alloy (CANDU Pressure tube), the longitudinal slip is easier than the circumferential one, resulting in the high creep rate. The irradiation creep also increases with increasing neutron fluence. The neutron irradiation increases the strength of the zirconium alloys but decreases their creep strength. In contrast to the out-reactor creep, the irradiation creep is little sensitive to temperature, resulting in the lower activation energy. The most important factor to affect the in-reactor and out-reactor creep of niobium containing alloys seems to be the solution hardening by Nb or Sn which is soluble in alpha-zirconium and the texture as well. Irradiation growth is the mechanism which is caused only by the irradiation. It becomes saturated at lower fluence than the critical fluence but beyond it, shows the break-away growth. The onset of accelerated irradiation growth corresponds with the c-dislocation loop formation, though its mechanism needs better understanding. Generally, the irradiation growth of Zr-Nb alloys increases with an increase in fluence, cold working, dislocation, density and temperature, and with a decrease in the grain size. 141 refs., 59 figs., 10 tabs. (Author)

  14. Creep-rupture reliability analysis

    Science.gov (United States)

    Peralta-Duran, A.; Wirsching, P. H.

    1985-01-01

    A probabilistic approach to the correlation and extrapolation of creep-rupture data is presented. Time temperature parameters (TTP) are used to correlate the data, and an analytical expression for the master curve is developed. The expression provides a simple model for the statistical distribution of strength and fits neatly into a probabilistic design format. The analysis focuses on the Larson-Miller and on the Manson-Haferd parameters, but it can be applied to any of the TTP's. A method is developed for evaluating material dependent constants for TTP's. It is shown that optimized constants can provide a significant improvement in the correlation of the data, thereby reducing modelling error. Attempts were made to quantify the performance of the proposed method in predicting long term behavior. Uncertainty in predicting long term behavior from short term tests was derived for several sets of data. Examples are presented which illustrate the theory and demonstrate the application of state of the art reliability methods to the design of components under creep.

  15. Computer Simulation of the Formation of Non-Metallic Precipitates During a Continuous Casting of Steel

    Directory of Open Access Journals (Sweden)

    Kalisz D.

    2016-03-01

    Full Text Available The authors own computer software, based on the Ueshima mathematical model with taking into account the back diffusion, determined from the Wołczyński equation, was developed for simulation calculations. The applied calculation procedure allowed to determine the chemical composition of the non-metallic phase in steel deoxidised by means of Mn, Si and Al, at the given cooling rate. The calculation results were confirmed by the analysis of samples taken from the determined areas of the cast ingot. This indicates that the developed computer software can be applied for designing the steel casting process of the strictly determined chemical composition and for obtaining the required non-metallic precipitates.

  16. Injury experience in nonmetallic mineral mining (except stone and coal), 1992

    Energy Technology Data Exchange (ETDEWEB)

    Reich, R.B; Hugler, E.C.

    1994-05-01

    This Mine Safety and Health Administration (MSHA) informational report reviews in detail the occupational injury and illness experience of nonmetallic mineral mining (except stone and coal) in the United States for 1992. Data reported by operators of mining establishments concerning work injuries are summarized by work location, accident classification, part of body injured, nature of injury, occupation, and principal type of mineral. Related information on employment, worktime, and operating activity also is presented. Data reported by independent contractors performing certain work at mining locations are depicted separately in this report. For ease of comparison with other metal and nonmetallic mineral mining industries and with coal mining, summary reference tabulations are included at the end of both the operator and the contractor sections of this report.

  17. Injury experience in nonmetallic mineral mining (except stone and coal), 1989

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    This Mine Safety and Health Administration (MSHA) informational report reviews in detail the occupational injury and illness experience of nonmetallic mineral mining (except stone and coal) in the United States for 1989. Data reported by operators of mining establishments concerning work injuries are summarized by work location, accident classification, part of body injured, nature of injury, occupation, and principal type of mineral. Related information on employment, worktime, and operating activity also is presented. Data reported by independent contractors performing certain work at mining locations are depicted separately in this report. For ease of comparison with other metal and nonmetallic mineral mining industries and with coal mining, summary reference tabulations are included at the end of both the operator and the contractor sections of this report. 3 figs., 46 tabs.

  18. Non-metallic catalysts for diamond synthesis under high pressure and high temperature

    Institute of Scientific and Technical Information of China (English)

    孙力玲; 吴奇; 戴道扬; 张君; 秦志成; 王文魁

    1999-01-01

    Recent results on conversion from graphite to diamond by aid of non-metallic catalysts are reviewed. The current status of experimental advances is presented and typical examples from relevant literature are provided for understanding the mechanism of the graphite-diamond conversion by aid of these non-metallic catalysts. Furthermore, a tendency of graphite-diamond transformation assisted by carbonates, sulfates or phosphorus under high pressure and high temperature has been investigated by calculating the activation energy and transformation probability of the carbon atoms over a potential barrier. It was found that the activation energy is highly sensitive to the catalyst chosen. The probability sequence of graphite-diamond transformation with these catalysts was put forward.

  19. Deformation by grain boundary sliding and slip creep versus diffusional creep

    Energy Technology Data Exchange (ETDEWEB)

    Ruano, O A; Sherby, O D; Wadsworth, J

    1998-11-04

    A review is presented of the debates between the present authors and other investigators regarding the possible role of diffusional creep in the plastic flow of polycrystalline metals at low stresses. These debates are recorded in eleven papers over the past seventeen years. ln these papers it has been shown that the creep rates of materials in the so-called "diffusional creep region" are almost always higher than those predicted by the diffusional creep theory. Additionally, the predictions of grain size effects and stress exponents from diffusional creep theory are often not found in the experimental data. Finally, denuded zones have been universally considered to be direct evidence for diffusional creep; but, those reported in the literature are shown to be found only under conditions where a high stress exponent is observed. Also, the locations of the denuded zones do not match those predicted. Alternative mechanisms are described in which diffusion-controlled dislocation creep and/or grain boundary sliding are the dominant deformation processes in low-stress creep. It is proposed that denuded zones are formed by stress-directed grain boundary migration with the precipitates dissolving in the moving grain boundaries. The above observations have led us to the conclusion that grain boundary sliding and slip creep are in fact the principal mechanisms for observations of plastic flow in the so-called "diffusional creep regions".

  20. On the prediction of long term creep strength of creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Mi; Wang, Qiao; Song, Xin-Li; Jia, Juan; Xiang, Zhi-Dong [Wuhan University of Science and Technology (China). The State Key Laboratory of Refractories and Metallurgy

    2016-02-15

    When the conventional power law creep equation is applied to rationalise the creep data of creep resistant steels, its parameters depend strongly on stress and temperature and hence cannot be used to predict long term creep properties. Here, it is shown that this problem can be resolved if it is modified to satisfy two boundary conditions, i.e. when σ (stress) = 0, ε{sub min} (minimum creep rate) = 0, and when σ = σ{sub TS} (tensile stress at creep temperature T), ε{sub min} = ∞. This can be achieved by substituting the reference stress σ{sub 0} in the conventional equation by the term (σ{sub TS} - σ). The new power law creep equation describing the stress and temperature dependence of minimum creep rate can then be applied to predict long term creep strength from data of short term measurements. This is demonstrated using the creep and tensile strength data measured for 11Cr-2W-0.4Mo-1Cu-Nb-V steel (tube).

  1. NON-METALLIC IMPURITIES AND FORMING OF THE STRUCTURE OF THE MODIFIED HIGH-MANGANESE STEEL

    Directory of Open Access Journals (Sweden)

    A. I. Garost

    2006-01-01

    Full Text Available The composition and morphology of chemical associations (non-metallic impurities and other ‘‘secondary” phases at modification of high-manganese steel by nitrogen and nitrideforming elements (vanadium are investigated. The optimal compositions of steel for production of castings are offered. The technology of the steel wear-resistance modification by vanadium of waste of industrial enterprises is worked out.

  2. The influence of grain boundary structure on diffusional creep

    DEFF Research Database (Denmark)

    Thorsen, Peter Anker; Bilde-Sørensen, Jørgen

    1999-01-01

    A Cu-2wt%Ni-alloy was deformed in tension in the diffusional creep regime (Nabarro-Herring creep). A periodic grid consisting of alumina was deposited on the surface of the creep specimen prior to creep. This makes it possible to separate the deformation caused by grain boundary sliding from...

  3. A Fully Non-Metallic Gas Turbine Engine Enabled by Additive Manufacturing

    Science.gov (United States)

    Grady, Joseph E.

    2015-01-01

    The Non-Metallic Gas Turbine Engine project, funded by NASA Aeronautics Research Institute, represents the first comprehensive evaluation of emerging materials and manufacturing technologies that will enable fully nonmetallic gas turbine engines. This will be achieved by assessing the feasibility of using additive manufacturing technologies to fabricate polymer matrix composite and ceramic matrix composite turbine engine components. The benefits include: 50 weight reduction compared to metallic parts, reduced manufacturing costs, reduced part count and rapid design iterations. Two high payoff metallic components have been identified for replacement with PMCs and will be fabricated using fused deposition modeling (FDM) with high temperature polymer filaments. The CMC effort uses a binder jet process to fabricate silicon carbide test coupons and demonstration articles. Microstructural analysis and mechanical testing will be conducted on the PMC and CMC materials. System studies will assess the benefits of fully nonmetallic gas turbine engine in terms of fuel burn, emissions, reduction of part count, and cost. The research project includes a multidisciplinary, multiorganization NASA - industry team that includes experts in ceramic materials and CMCs, polymers and PMCs, structural engineering, additive manufacturing, engine design and analysis, and system analysis.

  4. Advances in the assessment of creep data

    Energy Technology Data Exchange (ETDEWEB)

    Holdsworth, S.R.

    2010-07-01

    Many of the classical models representing the creep and rupture behaviour of metals were developed prior to and during the 1950s and 1960s, and their subsequent exploitation, in particular for the assessment of large creep property datasets, was initially limited by the capability of the analytical tools available at the time. The formation of ECCC (the European Creep Collaborative Committee) in 1991, with a main objective of providing reliable peer reviewed long-time creep property values for European Design and Product Standards, led to the development of rigorous assessment procedures such as PD6605 and DESA incorporating post assessment tests to verify: physical realism, effectiveness of model-fit within the range of the source experimental data, and extrapolation credibility. The first ECCC assessment recommendations published in 1996 undoubtedly provided a catalyst for others to exploit the availability of low cost, powerful desktop computers to develop rigorous methodologies for the physically realistic analysis of uniaxial and multi-axial data for the reliable and accurate characterisation of creep strain, and rupture strength and ductility properties. More recent improvements in data assessment methodologies have been driven by the need to effectively model the creep deformation and rupture characteristics of the complex new generation alloys and fabrications being designed to cater for the continually evolving requirements of modern advanced power plant. These advances in the assessment of creep data are reviewed. (orig.)

  5. ANALYSIS ON PSEUDO-STEADY INDENTATION CREEP

    Institute of Scientific and Technical Information of China (English)

    Hidenari Takagi; Ming Dao; Masami Fujiwara

    2008-01-01

    Theoretical analysis and finite element (FE) simulation have been carried out for a constant specific load rate (CSLR) indentation creep test.Analytical results indicate that both the representative stress and the indentation strain rate become constant after a transient period. Moreover,the FE simulation reveals that both the contours of equivalent stress and equivalent plastic strain rate underneath the indenter evolve with geometrical self-similarity.This suggests that pseudo-steady indentation creep occurs in the region beneath the indenter.The representative points in the region are defined as the ones with the equivalent stress equal to the representative stress.In addition,it is revealed that the proportionality between indentation strain rate and equivalent plastic strain rate holds at the representative points during the pseudo-steady inden tation creep of a power law material.A control volume (CV) beneath the indenter,which governs the indenter velocity,is identified.The size of the CV at the indented surface is approximately 2.5 times the size of the impression.The stress exponent for creep can be obtained from the pseudo steady indentation creep data.These results demonstrate that the CSLR testing technique can be used to evaluate creep parameters with the same accuracy as conventional uniaxial creep tests.

  6. Irradiation creep of dispersion strengthened copper alloy

    Energy Technology Data Exchange (ETDEWEB)

    Pokrovsky, A.S.; Barabash, V.R.; Fabritsiev, S.A. [and others

    1997-04-01

    Dispersion strengthened copper alloys are under consideration as reference materials for the ITER plasma facing components. Irradiation creep is one of the parameters which must be assessed because of its importance for the lifetime prediction of these components. In this study the irradiation creep of a dispersion strengthened copper (DS) alloy has been investigated. The alloy selected for evaluation, MAGT-0.2, which contains 0.2 wt.% Al{sub 2}O{sub 3}, is very similar to the GlidCop{trademark} alloy referred to as Al20. Irradiation creep was investigated using HE pressurized tubes. The tubes were machined from rod stock, then stainless steel caps were brazed onto the end of each tube. The creep specimens were pressurized by use of ultra-pure He and the stainless steel caps subsequently sealed by laser welding. These specimens were irradiated in reactor water in the core position of the SM-2 reactors to a fluence level of 4.5-7.1 x 10{sup 21} n/cm{sup 2} (E>0.1 MeV), which corresponds to {approx}3-5 dpa. The irradiation temperature ranged from 60-90{degrees}C, which yielded calculated hoop stresses from 39-117 MPa. A mechanical micrometer system was used to measure the outer diameter of the specimens before and after irradiation, with an accuracy of {+-}0.001 mm. The irradiation creep was calculated based on the change in the diameter. Comparison of pre- and post-irradiation diameter measurements indicates that irradiation induced creep is indeed observed in this alloy at low temperatures, with a creep rate as high as {approx}2 x 10{sup {minus}9}s{sup {minus}1}. These results are compared with available data for irradiation creep for stainless steels, pure copper, and for thermal creep of copper alloys.

  7. Small punch creep test in a 316 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Saucedo-Munoz, M. L.; Komazaki, S. I.; Hashida, T.; Lopez-Hirata, V. M.

    2015-03-30

    The small punch creep test was applied to evaluate the creep behavior of a 316 type austenitic stainless steel at temperatures of 650, 675 and 700 degree centigrade. The small punch test was carried out using a creep tester with a specimen size of 10x10x0.3 mm at 650, 675 and 700 degree centigrade using loads from 199 to 512 N. The small punch creep curves show the three stages found in the creep curves of the conventional uniaxial test. The conventional creep relationships which involve parameters such as creep rate, stress, time to rupture and temperature were followed with the corresponding parameters of small punch creep test and they permitted to explain the creep behavior in this steel. The mechanism and activation energy of the deformation process were the grain boundary sliding and diffusion, respectively, during creep which caused the intergranular fracture in the tested specimens. (Author)

  8. Low-temperature creep of austenitic stainless steels

    Science.gov (United States)

    Reed, R. P.; Walsh, R. P.

    2017-09-01

    Plastic deformation under constant load (creep) in austenitic stainless steels has been measured at temperatures ranging from 4 K to room temperature. Low-temperature creep data taken from past and unreported austenitic stainless steel studies are analyzed and reviewed. Creep at cryogenic temperatures of common austenitic steels, such as AISI 304, 310 316, and nitrogen-strengthened steels, such as 304HN and 3116LN, are included. Analyses suggests that logarithmic creep (creep strain dependent on the log of test time) best describe austenitic stainless steel behavior in the secondary creep stage and that the slope of creep strain versus log time is dependent on the applied stress/yield strength ratio. The role of cold work, strain-induced martensitic transformations, and stacking fault energy on low-temperature creep behavior is discussed. The engineering significance of creep on cryogenic structures is discussed in terms of the total creep strain under constant load over their operational lifetime at allowable stress levels.

  9. Creep of Refractory Fibers and Modeling of Metal and Ceramic Matrix Composite Creep Behavior

    Science.gov (United States)

    Tewari, S.N.

    1995-01-01

    Our concentration during this research was on the following subprograms. (1) Ultra high vacuum creep tests on 218, ST300 and WHfC tungsten and MoHfC molybdenum alloy wires, temperature range from 1100 K to 1500 K, creep time of 1 to 500 hours. (2) High temperature vacuum tensile tests on 218, ST300 and WHfC tungsten and MoHfC molybdenum alloy wires. (3) Air and vacuum tensile creep tests on polycrystalline and single crystal alumina fibers, such as alumina-mullite Nextel fiber, yttrium aluminum ganet (YAG) and Saphikon, temperature range from 1150 K to 1470 K, creep time of 2 to 200 hours. (4) Microstructural evaluation of crept fibers, TEM study on the crept metal wires, SEM study on the fracture surface of ceramic fibers. (5) Metal Matrix Composite creep models, based on the fiber creep properties and fiber-matrix interface zone formation.

  10. Negative creep during compressive creep of as-cast ZA27 alloy

    Institute of Scientific and Technical Information of China (English)

    魏晓伟; 沈保罗; 易勇

    2003-01-01

    The negative creep during compressive creep deformation of as-cast ZA27 alloy was investigated at the temperature range of 20-160℃ and at compressive stress levels from 50-137.5MPa with special apparatus. Results show that the negative creep in the alloy occurred respectively at 20℃ (50MPa, 87.5MPa and 100MPa), 60℃(50MPa and 87.5MPa) and 100℃(50MPa). According to the phase transformation and theoretical analysis, the negative creep resulted from volume expansion caused by four-phase transformation α+ε→T′+η in the alloy. The theoretical analysis is consistent with the experiment results. And the values of negative creep depended on the difference between the compressive creep deformation and the volume expansion.

  11. Correlation of Creep Behavior of Domal Salts

    Energy Technology Data Exchange (ETDEWEB)

    Munson, D.E.

    1999-02-16

    The experimentally determined creep responses of a number of domal salts have been reported in, the literature. Some of these creep results were obtained using standard (conventional) creep tests. However, more typically, the creep data have come from multistage creep tests, where the number of specimens available for testing was small. An incremental test uses abrupt changes in stress and temperature to produce several time increments (stages) of different creep conditions. Clearly, the ability to analyze these limited data and to correlate them with each other could be of considerable potential value in establishing the mechanical characteristics of salt domes, both generally and specifically. In any analysis, it is necessary to have a framework of rules to provide consistency. The basis for the framework is the Multimechanism-Deformation (M-D) constitutive model. This model utilizes considerable general knowledge of material creep deformation to supplement specific knowledge of the material response of salt. Because the creep of salt is controlled by just a few micromechanical mechanisms, regardless of the origin of the salt, certain of the material parameters are values that can be considered universal to salt. Actual data analysis utilizes the methodology developed for the Waste Isolation Pilot Plant (WIPP) program, and the response of a bedded pure WIPP salt as the baseline for comparison of the domal salts. Creep data from Weeks Island, Bryan Mound, West Hackberry, Bayou Choctaw, and Big Hill salt domes, which are all sites of Strategic Petroleum Reserve (SPR) storage caverns, were analyzed, as were data from the Avery Island, Moss Bluff, and Jennings salt domes. The analysis permits the parameter value sets for the domal salts to be determined in terms of the M-D model with various degrees of completeness. In turn this permits detailed numerical calculations simulating cavern response. Where the set is incomplete because of the sparse database, reasonable

  12. Simple Creep Test For Ceramic Fibers

    Science.gov (United States)

    Dicarlo, James A.; Morscher, Gregory N.

    1994-01-01

    Simple bend-stress-relaxation test yields information on creep-related properties of polycrystalline ceramic fibers. Determination of these properties important part of efforts to develop ceramic composite materials that retain mechanical strength and resistance to creep at high temperatures. Present test measures effects of time, temperature, and applied strain on creep-related relaxation of bend stress in ceramic fiber of almost any diameter in almost any environment, without need for contact sensors. Degree of relaxation of bend stress determined from radii of curvature.

  13. Modeling creep behavior of fiber composites

    Science.gov (United States)

    Chen, J. L.; Sun, C. T.

    1988-01-01

    A micromechanical model for the creep behavior of fiber composites is developed based on a typical cell consisting of a fiber and the surrounding matrix. The fiber is assumed to be linearly elastic and the matrix nonlinearly viscous. The creep strain rate in the matrix is assumed to be a function of stress. The nominal stress-strain relations are derived in the form of differential equations which are solved numerically for off-axis specimens under uniaxial loading. A potential function and the associated effective stress and effective creep strain rates are introduced to simplify the orthotropic relations.

  14. Creep of plain weave polymer matrix composites

    Science.gov (United States)

    Gupta, Abhishek

    Polymer matrix composites are increasingly used in various industrial sectors to reduce structural weight and improve performance. Woven (also known as textile) composites are one class of polymer matrix composites with increasing market share mostly due to their lightweight, their flexibility to form into desired shape, their mechanical properties and toughness. Due to the viscoelasticity of the polymer matrix, time-dependent degradation in modulus (creep) and strength (creep rupture) are two of the major mechanical properties required by engineers to design a structure reliably when using these materials. Unfortunately, creep and creep rupture of woven composites have received little attention by the research community and thus, there is a dire need to generate additional knowledge and prediction models, given the increasing market share of woven composites in load bearing structural applications. Currently, available creep models are limited in scope and have not been validated for any loading orientation and time period beyond the experimental time window. In this thesis, an analytical creep model, namely the Modified Equivalent Laminate Model (MELM), was developed to predict tensile creep of plain weave composites for any orientation of the load with respect to the orientation of the fill and warp fibers, using creep of unidirectional composites. The ability of the model to predict creep for any orientation of the load is a "first" in this area. The model was validated using an extensive experimental involving the tensile creep of plain weave composites under varying loading orientation and service conditions. Plain weave epoxy (F263)/ carbon fiber (T300) composite, currently used in aerospace applications, was procured as fabrics from Hexcel Corporation. Creep tests were conducted under two loading conditions: on-axis loading (0°) and off-axis loading (45°). Constant load creep, in the temperature range of 80-240°C and stress range of 1-70% UTS of the

  15. Linear logarithmic model for concrete creep:II. Prediction formulas for description of creep behaviour

    OpenAIRE

    Larson, Mårten; Jonasson, Jan-Erik

    2003-01-01

    A reliable modelling of the young concrete creep behaviour is of great importance for consistent thermal crack risk estimations that shall contribute to assure a desired service lifetime and function of a structure. All-embracing creep tests aimed for thermal stress analyses are often very time consuming and thereby also costly to perform. Therefore thermal stress calculations in everyday engineering practice are often performed with standard sets of creep data involving no or very limited la...

  16. Creep strength and rupture ductility of creep strength enhanced ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Kushima, Hideaki; Sawada, Kota; Kimura, Kazuhiro [National Inst. for Materials Science, Tsukuba, Ibaraki (Japan)

    2010-07-01

    Creep strength and rupture ductility of Creep Strength Enhanced Ferritic (CSEF) steels were investigated from a viewpoint of stress dependence in comparison with conventional low alloy ferritic creep resistant steels. Inflection of stress vs. time to rupture curve was observed at 50% of 0.2% offset yield stress for both CSEF and conventional ferritic steels. Creep rupture ductility tends to decrease with increase in creep exposure time, however, those of conventional low alloy steels indicate increase in the long-term. Creep rupture ductility of the ASME Grades 92 and 122 steels indicates drastic decrease with decrease in stress at 50% of 0.2% offset yield stress. Stress dependence of creep rupture ductility of the ASME Grades 92 and 122 steels is well described by stress ratio to 0.2% offset yield stress, regardless of temperature. Drop of creep rupture ductility is caused by inhomogeneous recovery at the vicinity of prior austenite grain boundary, and remarkable drop of creep rupture ductility of CSEF steels should be derived from those stabilized microstructure. (orig.)

  17. Creep Aging Behavior Characterization of 2219 Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    Lingfeng Liu

    2016-06-01

    Full Text Available In order to characterize the creep behaviors of 2219 aluminum alloy at different temperatures and stress levels, a RWS-50 Electronic Creep Testing Machine (Zhuhai SUST Electrical Equipment Company, Zhuhai, China was used for creep experiment at temperatures of 353~458 k and experimental stresses of 130~170 MPa. It was discovered that this alloy displayed classical creep curve characteristics in its creep behaviors within the experimental parameters, and its creep value increased with temperature and stress. Based on the creep equation of hyperbolic sine function, regression analysis was conducted of experimental data to calculate stress exponent, creep activation energy, and other related variables, and a 2219 aluminum alloy creep constitutive equation was established. Results of further analysis of the creep mechanism of the alloy at different temperatures indicated that the creep mechanism of 2219 aluminum alloy differed at different temperatures; and creek characteristics were presented in three stages at different temperatures, i.e., the grain boundary sliding creep mechanism at a low temperature stage (T < 373 K, the dislocation glide creep mechanism at a medium temperature stage (373 K ≤ T < 418 K, and the dislocation climb creep mechanism at a high temperature stage (T ≥ 418 K. By comparative analysis of the fitting results and experiment data, they were found to be in agreement with the experimental data, revealing that the established creep constitutive equation is suitable for different temperatures and stresses.

  18. Documentation for the viscoplastic and creep program

    DEFF Research Database (Denmark)

    Bellini, Anna

    2004-01-01

    of this workpackage is to simulate creep behavior of aluminum cast samples subjected to high temperature. In this document a two-state variables unified model is applied in order to simulate creep behavior and time-dependent metallurgical changes. The fundamental assumption of the unified theory is that creep...... and viscoplasticity, which are both irreversible strains developed because of dislocations motion in the material structure, can be modelled through the implementation of a similar plastic strain velocity law, generally called flow rule. The document shows how to obtain the material data needed for the simulation...... is run using the material data obtained through the mentioned experimental study. The results obtained for the simulation of tensile tests and of creep tests are compared with experimental curves, showing a good agreement. Moreover, the document describes the results obtained during the first...

  19. Implications of Jeffreys-Lomnitz Transient Creep

    Science.gov (United States)

    Strick, Ellis

    1984-01-01

    In 1958 Jeffreys proposed a power law generalization of the logarithmic transient creep earlier attributed to Lomnitz. Although Jeffreys' power law form was admittedly defective in that it became unbounded at infinite time, he did apply it to the viscoelastic behavior of the earth-moon system. Since then it has been successfully applied by many investigators to mantle rehology and Chandler wobble. Experimental seismic studies indicate that most rock types exhibit the almost constant Q behavior which Lomnitz showed to be associated with his logarithmic creep. In this paper, we study not only the Q behavior related to Jeffreys' power law creep but also other mechanical properties such as a precise spring-dashpot ladder network realization are developed. In addition, a very simple physically realizable modification of this ladder network leads to a boundedness at long times of Jeffreys' creep in a manner which does not affect his successful application at finite times.

  20. Rock bending creep and disturbance effects

    Institute of Scientific and Technical Information of China (English)

    付志亮; 郑颖人; 刘元雪

    2008-01-01

    The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test system,and the constitutive equations were established.It is found that fracture morphology of rock beams under no disturbance load is regular,cracking position of fractures is on part of loading concentration,the crack starts from a neutral plane.However,fracture morphology of rock beams under disturbance load is irregular,cracking position of fractures deviates from a neutral plane.Delayed instability of rock beam occurs for some time under constant disturbance load.When disturbance load is beyond a certain range,suddenly instability of occurs rock beam in a certain time.The results show that there is a guiding significance for creep stability in the geotechnical engineering fields.

  1. Analytic Creep Durability of Rotating Uniform Disks

    Directory of Open Access Journals (Sweden)

    Yuriy Nyashin

    1998-01-01

    Full Text Available Turbine disks of aircraft engines in operation are subjected to alternating thermocyclic deformation under high temperatures. Operation gives rise to sufficiently high stresses and subsequent creep damaging effects.

  2. Inversion of hysteresis and creep operators

    Science.gov (United States)

    Krejčí, Pavel; Al Janaideh, Mohammad; Deasy, Fergal

    2012-05-01

    The explicit inversion formula for rate dependent Prandtl-Ishlinskii operators is extended to cases without the threshold dilation condition. This solves a problem in hysteresis and creep modeling of magnetostrictive behavior.

  3. Creep of frozen soil by damage mechanics

    Institute of Scientific and Technical Information of China (English)

    苗天德; 魏雪霞; 张长庆

    1995-01-01

    A microstructure damage theory for creep of frozen soil under the frame of damage mechan-ics is presented.Based on the test study and microscope observation,several internal variables are chosen tocharacterize the microstructure changes and the evolution equations of these internal variables are developed.The theory can describe both the "hardening" and "softening" behavior in the creep process.A detailed analysis hasbeen made for the uniaxial compressure and compared with the test data.

  4. Creep fatigue assessment for EUROFER components

    Energy Technology Data Exchange (ETDEWEB)

    Özkan, Furkan, E-mail: oezkan.furkan@partner.kit.edu; Aktaa, Jarir

    2015-11-15

    Highlights: • Design rules for creep fatigue assessment are developed to EUROFER components. • Creep fatigue assessment tool is developed in FORTRAN code with coupling MAPDL. • Durability of the HCPB-TBM design is discussed under typical fusion reactor loads. - Abstract: Creep-fatigue of test blanket module (TBM) components built from EUROFER is evaluated based on the elastic analysis approach in ASME Boiler Pressure Vessel Code (BPVC). The required allowable number of cycles design fatigue curve and stress-to-rupture curve to estimate the creep-fatigue damage are used from the literature. Local stress, strain and temperature inputs for the analysis of creep-fatigue damage are delivered by the finite element code ANSYS utilizing the Mechanical ANSYS Parametric Design Language (MAPDL). A developed external FORTRAN code used as a post processor is coupled with MAPDL. Influences of different pulse durations (hold-times) and irradiation on creep-fatigue damage for the preliminary design of the Helium Cooled Pebble Bed Test Blanket Module (HCPB-TBM) are discussed for the First Wall component of the TBM box.

  5. Inclusive pedagogy

    DEFF Research Database (Denmark)

    Korsgaard, Morten Timmermann; Skov Mortensen, Stig

    2015-01-01

    This article will present a case for a shift in perspective in inclusive education research towards a continentally inspired approach. Drawing on the age old distinction between continental and Anglo-American educational research the aim is to flesh out what a shift to a continental approach will...

  6. Inclusive pedagogy

    DEFF Research Database (Denmark)

    Korsgaard, Morten Timmermann; Skov Mortensen, Stig

    This article will present a case for a shift in perspective in inclusive education research towards a continentally inspired approach. Drawing on the age old distinction between continental and Anglo-American educational research the aim is to flesh out what a shift to a continental approach will...

  7. Inclusion Analysis

    CERN Document Server

    Colver, David

    2010-01-01

    Inclusion analysis is the name given by Operis to a black box testing technique that it has found to make the checking of key financial ratios calculated by spreadsheet models quicker, easier and more likely to find omission errors than code inspection.

  8. ARE INCLUSIVE DESIGNERS DESIGNING INCLUSIVELY?

    DEFF Research Database (Denmark)

    Herriott, Richard

    2013-01-01

    A large body of literature exists relating to Inclusive Design. The literature can be divided into theory concerning methodology and case studies concerning practice. With such a large body of theoretical literature available, the question arises as to how closely practice matches that theory....... This paper is a survey of the methods used in the execution of self-declared inclusively design products based on an analysis of academic papers, posters and oral presentations. The case studies are divided into two groups, product design and assistive technology. Design steps were assigned to six categories...

  9. SIMULATION PROCESS OF REMOVING NON-METALLIC INCLUSIONS IN ALUMINUM ALLOYS USING THE PROGRAM FLOW-3D

    Directory of Open Access Journals (Sweden)

    N. V. Sletova

    2013-01-01

    Full Text Available The perspective materials for making fining preparations for the silumins are the calcium and strontium carbonates from the environmental safety point of view are shown. Principle possibility of using dispersed carbonates in the fining mixtures is confirmed by late inoculation process research using simulation FLOW-3D.The high efficiency of the fining mixture with the inoculants effect is confirmed by the industrial tests

  10. Brittle and compaction creep in porous sandstone

    Science.gov (United States)

    Heap, Michael; Brantut, Nicolas; Baud, Patrick; Meredith, Philip

    2015-04-01

    Strain localisation in the Earth's crust occurs at all scales, from the fracture of grains at the microscale to crustal-scale faulting. Over the last fifty years, laboratory rock deformation studies have exposed the variety of deformation mechanisms and failure modes of rock. Broadly speaking, rock failure can be described as either dilatant (brittle) or compactive. While dilatant failure in porous sandstones is manifest as shear fracturing, their failure in the compactant regime can be characterised by either distributed cataclastic flow or the formation of localised compaction bands. To better understand the time-dependency of strain localisation (shear fracturing and compaction band growth), we performed triaxial deformation experiments on water-saturated Bleurswiller sandstone (porosity = 24%) under a constant stress (creep) in the dilatant and compactive regimes, with particular focus on time-dependent compaction band formation in the compactive regime. Our experiments show that inelastic strain accumulates at a constant stress in the brittle and compactive regimes leading to the development of shear fractures and compaction bands, respectively. While creep in the dilatant regime is characterised by an increase in porosity and, ultimately, an acceleration in axial strain to shear failure (as observed in previous studies), compaction creep is characterised by a reduction in porosity and a gradual deceleration in axial strain. The overall deceleration in axial strain, AE activity, and porosity change during creep compaction is punctuated by excursions interpreted as the formation of compaction bands. The growth rate of compaction bands formed during creep is lower as the applied differential stress, and hence background creep strain rate, is decreased, although the inelastic strain required for a compaction band remains constant over strain rates spanning several orders of magnitude. We find that, despite the large differences in strain rate and growth rate

  11. Creep and creep damage in copper under uniaxial/multiaxial loading

    Energy Technology Data Exchange (ETDEWEB)

    Auerkari, Pertti; Holmstroem, Stefan; Salonen, Jorma [VTT Industrial Systems, Espoo (Finland)

    2003-08-01

    Multiaxial tensile loading is known to enhance accumulation of creep cavitation and cracking damage in polycrystalline metals under given equivalent loading stress and temperature. To study whether this could potentially lead to significant creep damage under long-term repository conditions, multiaxial creep testing and damage evaluation has been initiated. Multiaxial creep testing of OFP copper has been performed using sharp notches in compact tension (CT) specimens. The loading conditions (reference stress and temperature) have been selected to produce an estimated time to either failure or at least to measurable creep damage within the maximum intended testing time or about 5000 hours. For appropriate material and finite element (FE) modelling to set correct loading in multiaxial testing and to obtain a reasonable stress state conversion, parallel uniaxial creep testing has also been performed on the same material. In addition, to support the uniaxial testing and materials modelling, an overall creep rupture life assessment was performed for OFP copper, based on ECCC guidelines and PD6605 including uniaxial creep testing data from the literature. To observe potential creep damage, the multiaxial tests have been also interrupted for metallography about every 2000 h of testing, and inspected by scanning electron microscopy (SEM) for indications of damage. For comparison, metallographic inspection including transmission electron microscopy (TEM) was performed for the same material in as-new state. The initial as-new state as well as later tested states of the material appear to involve grain boundary phases, which are sometimes apparent in SEM but can also require TEM to be resolved. Until now, the multiaxial creep test at lowest reference stress (46 MPa/150 deg C) has been interrupted at 3000, 5000 and 7000 h of testing for inspection in SEM. In these inspections, only occasional scattered evidence of some possible cavitation damage has been found so far. On the

  12. Demonstration of creep during filtration

    DEFF Research Database (Denmark)

    Christensen, Morten Lykkegaard; Bugge, Thomas Vistisen; Kirchheiner, Anders Løvenbalk

    The classical filtration theory assumes a unique relationship between the local filter cake porosity and the local effective pressure. For a number of compressible materials, it has however been observed that during the consolidation stage this may not be the case. It has been found that the prod......The classical filtration theory assumes a unique relationship between the local filter cake porosity and the local effective pressure. For a number of compressible materials, it has however been observed that during the consolidation stage this may not be the case. It has been found...... that the production of filtrate also depends on the characteristic time for the filter cake solids to deform. This is formulated in the Terzaghi-Voigt model in which a secondary consolidation is introduced. The secondary consolidation may be visualized by plots of the relative cake deformation (U) v.s. the square...... magnitude as the primary consolidation (defined by the hydraulic retardation), the creep phenomenon may occur during filtration. This will lead to Ruth's plots characterized by a concave with two (more or less) distinct slopes. The slopes are defined by the relationship between the porosity...

  13. A Fully Non-metallic Gas Turbine Engine Enabled by Additive Manufacturing

    Science.gov (United States)

    Grady, Joseph E.

    2014-01-01

    The Non-Metallic Gas Turbine Engine project, funded by NASA Aeronautics Research Institute (NARI), represents the first comprehensive evaluation of emerging materials and manufacturing technologies that will enable fully nonmetallic gas turbine engines. This will be achieved by assessing the feasibility of using additive manufacturing technologies for fabricating polymer matrix composite (PMC) and ceramic matrix composite (CMC) gas turbine engine components. The benefits of the proposed effort include: 50 weight reduction compared to metallic parts, reduced manufacturing costs due to less machining and no tooling requirements, reduced part count due to net shape single component fabrication, and rapid design change and production iterations. Two high payoff metallic components have been identified for replacement with PMCs and will be fabricated using fused deposition modeling (FDM) with high temperature capable polymer filaments. The first component is an acoustic panel treatment with a honeycomb structure with an integrated back sheet and perforated front sheet. The second component is a compressor inlet guide vane. The CMC effort, which is starting at a lower technology readiness level, will use a binder jet process to fabricate silicon carbide test coupons and demonstration articles. The polymer and ceramic additive manufacturing efforts will advance from monolithic materials toward silicon carbide and carbon fiber reinforced composites for improved properties. Microstructural analysis and mechanical testing will be conducted on the PMC and CMC materials. System studies will assess the benefits of fully nonmetallic gas turbine engine in terms of fuel burn, emissions, reduction of part count, and cost. The proposed effort will be focused on a small 7000 lbf gas turbine engine. However, the concepts are equally applicable to large gas turbine engines. The proposed effort includes a multidisciplinary, multiorganization NASA - industry team that includes experts in

  14. New technology for recovering residual metals from nonmetallic fractions of waste printed circuit boards.

    Science.gov (United States)

    Zhang, Guangwen; He, Yaqun; Wang, Haifeng; Zhang, Tao; Wang, Shuai; Yang, Xing; Xia, Wencheng

    2017-03-23

    Recycling of waste printed circuit boards is important for environmental protection and sustainable resource utilization. Corona electrostatic separation has been widely used to recycle metals from waste printed circuit boards, but it has poor separation efficiency for finer sized fractions. In this study, a new process of vibrated gas-solid fluidized bed was used to recycle residual metals from nonmetallic fractions, which were treated using the corona electrostatic separation technology. The effects of three main parameters, i.e., vibration frequency, superficial air flow velocity, and fluidizing time on gravity segregation, were investigated using a vibrating gas-solid fluidized bed. Each size fraction had its own optimum parameters. Corresponding to their optimal segregation performance, the products from each experiment were analyzed using an X-ray fluorescence (XRF) and a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). From the results, it can be seen that the metal recoveries of -1+0.5mm, -0.5+0.25mm, and -0.25mm size fractions were 86.39%, 82.22% and 76.63%, respectively. After separation, each metal content in the -1+0.5 or -0.5+0.25mm size fraction reduced to 1% or less, while the Fe and Cu contents are up to 2.57% and 1.50%, respectively, in the -0.25mm size fraction. Images of the nonmetallic fractions with a size of -0.25mm indicated that a considerable amount of clavate glass fibers existed in these nonmetallic fractions, which may explain why fine particles had the poorest segregation performance.

  15. Evidence of phase nucleation during olivine diffusion creep: A new perspective for mantle strain localisation

    Science.gov (United States)

    Précigout, Jacques; Stünitz, Holger

    2016-12-01

    For the past decades, grain size reduction leading to diffusion creep in olivine is believed to be a very important process for strain localisation in the lithospheric mantle. However, the mechanisms of grain size reduction in this regime are still poorly understood (e.g., Platt, 2015). Here we show new experimental results that document grain size reduction and material weakening during wet olivine diffusion creep. While occurring for both, mono-phase and two-phase aggregates, grain size reduction is coeval with strain localisation and local phase mixing in olivine-pyroxene aggregates. Based on evidence of fluid inclusions and cracks filled with a fine-grained phase mixture, we conclude that grain size reduces as a result of fluid-assisted nucleation that takes place in the presence of an aqueous fluid during diffusion creep. Cavitation induced by grain boundary sliding (creep cavitation) can be inferred, and may play a critical role for olivine grain size reduction. Amongst their implications for rock rheology in general, our findings highlight a key process for strain localisation in the ductile uppermost mantle.

  16. The investigation of expanded polystyrene creep behaviour

    Directory of Open Access Journals (Sweden)

    Zhukov Aleksey

    2017-01-01

    Full Text Available The results obtained in long-term testing under constant compressive stress of the cut from the Slabs EPS 50/100 and EPS 150 with the density ranging from 15 to 24 kg/m3, which were manufactured by the same manufacturer by foaming EPS solid granules (beads in closed volume. The creep strain of the above described specimens was used as a criterion for estimating the deformability of the EPS slabs under long-term compressive stress. It was measured using special stands EN 1606, maintaining constant stress during the fixed time interval tn=122 days. Creep strains were determined by the methods described in EN 1606 for constant stress σc=0.35σ10% (compressive stress σ10% was determined in accordance with EN 826:2013. The long-term compressive stress measurement error did not exceed 1 %, while the creep strain measurement error was not larger than 0,005 mm. The tests were conducted at the ambient temperature of (23±2°С and relative humidity of (50±5 %.The long-term constant compressive load σc=0.35σ10%. The method of mathematical and statistical experimental design optimization models taking into account the thickness of specimens is proposed to determine the creep compliance Ic (tn the creep strain εc (tn and predictive point estimate of creep strain εc (T. Graphical interpretation of the abstained models is also presented. It should be noted that the abstained equations may be used in practice for estimating the creep strains at time tn=122 days and predictive estimates of εc (T for the load time of 10 years.

  17. PENGARUH RANGKAK CREEP PADA BANGUNAN TINGGI

    Directory of Open Access Journals (Sweden)

    David Budiono

    2003-01-01

    Full Text Available Inelastic deformation due to creep can cause dramatic change of end moment of beams. In this study the influence of creep to end moments is compared with the ones calculated using direct and sequential load methods. An approximate method using Equivalent Modulus of Elasticity is proposed. Four shear wall frame buildings, 10, 20, 30, and 40 stories with 30 cm shear wall are subjected to 5, 10, 15, and 20 years creep. It is shown that the difference between the 5, 10, 15, and 20 years creep are not significant. Compared to the sequential method, the direct method gives a better result to the creep. It is also shown that except for the 10 story building, the end moments caused by the development of creep deformation can cause cracks, thus the ability of the beams to redistribute the end moment must be assured. Abstract in Bahasa Indonesia : Perubahan bentuk inelastis yang disebabkan oleh rangkak (creep dapat menyebabkan perubahan momen pada tumpuan balok. Penelitian ini mempelajari pengaruh rangkak dan membandingkan hasil perhitungan yang diperoleh terhadap metode pembebanan langsung dan pembebanan sequential. Untuk memperhitungkan pengaruh rangkak, diusulkan suatu metode penyederhanaan di mana digunakan konsep Modulus Elastisitas Ekivalen. Dalam penelitian ini ditinjau 4 buah bangunan, yaitu bangunan 10, 20, 30 dan 40 lantai dengan dinding geser tebal 30 cm., pengaruh rangkak diperhatikan pada saat bangunan berumur 5, 10, 15, dan 20 tahun. Hasil penelitian menunjukkan bahwa tidak ada perbedaan yang berarti antara rangkak 5, 10, 15, dan 20 tahun. Dibandingkan dengan metode sequential, metode pembebanan langsung lebih mendekati hasil yang diberikan perhitungan dengan memasukkan pengaruh rangkak. Juga ditunjukkan bahwa selain pada bangunan 10 lantai, akibat rangkak akan terjadi retak pada beberapa tumpuan, sehingga dalam perencanaan harus dimungkinkan terjadinya redistribusi momen dari tumpuan ke lapangan.

  18. Coexistence of metallic and nonmetallic charge transport in PrBa2Cu3O7

    Science.gov (United States)

    Lee, Mark; Suzuki, Y.; Geballe, T. H.

    1995-06-01

    Magnetotransport measurements on highly oriented thin films of PrBa2Cu3O7 demonstrate a unique coexistence of nonmetallic hopping conduction with metallic Boltzmann transport. At high temperature (T>10 K) hopping transport dominates, but when the inelastic conduction freezes out at low temperature, metallic behavior can be distinguished. The hopping conduction is assigned to the CuO2 planes, while the Boltzmann transport arises from the CuO chain structure, in agreement with recent electronic-structure calculations.

  19. Separation of the metallic and non-metallic fraction from printed circuit boards employing green technology.

    Science.gov (United States)

    Estrada-Ruiz, R H; Flores-Campos, R; Gámez-Altamirano, H A; Velarde-Sánchez, E J

    2016-07-05

    The generation of electrical and electronic waste is increasing day by day; recycling is attractive because of the metallic fraction containing these. Nevertheless, conventional techniques are highly polluting. The comminution of the printed circuit boards followed by an inverse flotation process is a clean technique that allows one to separate the metallic fraction from the non-metallic fraction. It was found that particle size and superficial air velocity are the main variables in the separation of the different fractions. In this way an efficient separation is achieved by avoiding the environmental contamination coupled with the possible utilization of the different fractions obtained. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Theory and Practice of Oxide Inclusion Composition and Morphology Control in Spring Steel Production

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In order to control the composition, morphology and size distribution of oxide inclusions in spring steel, the relationship between the content or activity of aluminum and calcium in molten steel and compositions of oxide inclusion precipitated at different temperatures was determined based on thermodynamic equilibrium for spring steel 60Si2MnA, and has been verified by practice. The size distribution of non-metallic inclusions electrolytically extracted from specimens of hot rolled spring steel was determined by image analyzer. The results show that there are a great deal of large inclusions in spring steel produced by the conventional process, and the quantity and the size of large inclusions in spring steel produced by new process are largely reduced. As a result, the fatigue properties of the spring steel produced by new process are highly improved, and the ratio of σ-1/σb is raised from 0.451 to 0.468.

  1. Qualitative and quantitative determination of micro-inclusions by automated SEM/EDX analysis.

    Science.gov (United States)

    Nuspl, Markus; Wegscheider, Wolfhard; Angeli, Johann; Posch, Wilhelm; Mayr, Michael

    2004-06-01

    With the help of an automated SEM/EDX analysis system non-metallic micro-inclusions in steel can be detected on a metallographically prepared surface area. The system makes it possible to determine position, size, shape and composition of each particle. Usually more than 1000 inclusions are found on one scan area. Therefore a new offline evaluation method has been developed to classify the large amount of inclusions and calculate specific size and shape data. A summary sheet is created to show the area contents and the mean values of all important properties for each class. Size and XY distributions as well as binary and ternary phase diagrams are drawn to depict the results. The strengths of this analytical technique are demonstrated by evaluation of an LC (low-carbon) steel. Alumina, common spinel, sulfide and oxisulfide inclusions could be identified as dominant inclusion types in LC steel.

  2. Uniaxial and Multiaxial Creep Testing of Copper

    Energy Technology Data Exchange (ETDEWEB)

    Auerkari, Pertti; Holmstroem, Stefan; Veivo, Juha; Salonen, Jorma; Nenonen, Pertti; Laukkanen, Anssi [VTT Industrial Systems, Helsinki (Finland)

    2003-12-01

    Multiaxial (compact tension, CT) creep testing has been performed for copper with 79 ppm phosphorus and 60 ppm oxygen. The test load levels were selected according to results from preceding uniaxial creep testing and FE analysis of the CT specimens. Interrupted testing was used for metallographic inspection of the specimens for creep damage. After 7,900 h and 10,300 h of testing at 150 deg C and 46 MPa (reference stress), inspected CT specimens showed cavity indications with a low maximum density (<100/mm{sup 2}) and a typical maximum dimension of less than about 1 {mu}m near the notch tip. From previous experience on creep cavitation damage, the expected minimum life to crack initiation at the notch tip would be at least 40,000 hours, but could be considerably longer because the cavity indications are suspected to originate at least partly from precipitates in specimen preparation. The interrupted testing of CT specimens also showed a 'segregation zone' along some grain boundaries, mainly near the notch tip. This zone appears to contain more P and O than the surrounding matrix, but less than the narrow grain boundary films that are already present in the as-new material. The zone is readily etched and shows a relatively sharp edge towards the matrix without an obvious phase boundary. Using converted multiaxial (CT) testing results, the predicted isothermal uniaxial creep life at 150 deg C/46 MPa is about 1,900 years. The corresponding creep life directly predicted from uniaxial data is 3,100 years, when estimated from a parametric best fit expression according to PD6605. Although the two results are satisfactorily within a factor of two in time, the uncertainties in the extended extrapolations remain large. Further testing is recommended, with at least two creep enhancing factors present. Such testing could include notched creep testing at 120-180 deg C in a corrosive environment, and notched model vessel creep testing at elevated pressure. It is also

  3. Analysis of Superheater Work Under Creep Conditions

    Directory of Open Access Journals (Sweden)

    Piotr Duda

    2015-03-01

    Full Text Available The aim of this article is work modelling of superheater SH3. It is made of the austenitic stainless steel Super 304H. Its design temperature T is 604 C, and the design pressure P acting on the inner surface of the pipes is 284 bar. The high temperature is the reason of the superheater work under creep conditions. In this article calculations of the optimally mounted coil superheater SH3 are presented. The calculations are carried out first on the basis of the applicable European standards and with the help of the Auto Pipe program. Then, calculations are performed using the ANSYS program based on conducted creep tests and proposed creep equation. The coefficients in creep equation are determined based on the research conducted at the Instytut Metalurgii Żelaza in Gliwice. The model approximates the creep strain as the function of time and stress and this function is presented in the form of a three-dimensional surface . The results of calculations by both methods will be compared and conclusions will be presented. The performed analyzes can estimate the superheater coil remnant life and the usage after the selected time of its operation.

  4. Creep curve modelling of a conventionally cast nickel base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Lupinc, V.; Maldini, M. [CNR - IENI, Milan (Italy); Poggio, E.; Vacchieri, E. [Ansaldo Energia S.p.A., Genoa (Italy)

    2010-07-01

    Constant load creep tests on Rene 80, a nickel base superalloy for gas turbine blade application, were run in the temperature interval 800-950 C with applied stresses producing rupture times up to 1000 h. Creep curves are generally dominated by a long accelerating/tertiary creep that follows a relatively small decelerating/primary creep. No steady state stage has been observed. Analysis of the creep curves has shown that a single damage parameter can describe the long accelerating/tertiary state in the explored temperature range. The damage appears to be dependent on the accumulated creep strain and, as a first approximation, independent on the applied stress and temperature. The whole creep curve, primary and tertiary stages, has been modelled by a simple set of coupled differential equations obtained using the formalism of the Continuum Damage Mechanics. The proposed set of equations has an analytical solution, strain vs. time, for creep curves at constant temperature and stress. (orig.)

  5. Effect of loading rate on creep of phosphorous doped copper

    Energy Technology Data Exchange (ETDEWEB)

    Andersson-Oestling, Henrik C.M.; Sandstroem, Rolf (Swerea KIMAB (Sweden))

    2011-12-15

    Creep testing of copper intended for nuclear waste disposal has been performed on continuous creep tests machines at a temperature of 75 deg C. The loading time has been varied from 1 hour to 6 months. The rupture strain including both loading and creep strains does not differ from traditional dead weight lever creep test rigs. The loading strain increases with increasing loading time, at the expense of the creep strain. The time dependence of the creep strain has been modelled taking athermal plastic deformation and creep into account. During loading the contribution to the strain from the athermal plastic deformation dominates until the stress is close to the constant load level. When the constant load has been reached there is no more athermal strain and all of the strain comes from creep

  6. Influence of creep and cyclic oxidation in thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Seiler, Philipp; Baeker, Martin; Roesler, Joachim [Technische Univ. Braunschweig (Germany). Inst. fuer Werkstoffe

    2012-01-15

    The lifetime of thermal barrier coating systems is limited by cracks close to the interfaces, causing delamination. To study the failure mechanisms, a simplified model system is analysed which consists of a bond-coat bulk material, a thermally grown oxide, and an yttria-stabilised zirconia topcoat. The stresses in the model system are calculated using a finite element model which covers the simulation of full thermal cycles, creep in all layers, and the anisotropic oxidation during dwelling. Creep in the oxide and the thermal barrier coating is varied with the use of different creep parameter sets. The influence of creep in the bondcoat is analysed by using two different bond-coat materials: fast creeping Fecralloy and slow creeping oxide dispersion strengthened MA956. It is shown that creep in the bondcoat influences the lifetime of the coatings. Furthermore, a fast creeping thermally grown oxide benefits the lifetime of the coating system. (orig.)

  7. Creep Properties of Walikukun (Schouthenia ovata Timber Beams

    Directory of Open Access Journals (Sweden)

    Ali Awaludin

    2016-09-01

    Full Text Available This study presents an evaluation of creep constants of Walikukun (Schoutheniaovata timber beams when rheological model of four solid elements, which is obtained byassembling Kelvin and Maxwell bodies in parallel configuration, was adopted. Creep behaviorobtained by this method was further discussed and compared with creep behavior developedusing phenomenological model of the previous study. Creep data of previous study was deformationmeasurement of Walikukun beams having cross-section of 15 mm by 20 mm with a clearspan of 550 mm loaded for three weeks period under two different room conditions: with andwithout Air Conditioner. Creep behavior given by both four solid elements model and phenomenological(in this case are power functions had good agreement during the period of creepmeasurement, but they give different prediction of creep factor beyond this period. The powerfunction of phenomenological model could give a reasonable creep prediction, while for the foursolid elements model a necessary modification is required to adjust its long-term creep behavior.

  8. Homogenized Creep Behavior of CFRP Laminates at High Temperature

    Science.gov (United States)

    Fukuta, Y.; Matsuda, T.; Kawai, M.

    In this study, creep behavior of a CFRP laminate subjected to a constant stress is analyzed based on the time-dependent homogenization theory developed by the present authors. The laminate is a unidirectional carbon fiber/epoxy laminate T800H/#3631 manufactured by Toray Industries, Inc. Two kinds of creep analyses are performed. First, 45° off-axis creep deformation of the laminate at high temperature (100°C) is analyzed with three kinds of creep stress levels, respectively. It is shown that the present theory accurately predicts macroscopic creep behavior of the unidirectional CFRP laminate observed in experiments. Then, high temperature creep deformations at a constant creep stress are simulated with seven kinds of off-axis angles, i.e., θ = 0°, 10°, 30°, 45°, 60°, 75°, 90°. It is shown that the laminate has marked in-plane anisotropy with respect to the creep behavior.

  9. Carbonic inclusions

    Science.gov (United States)

    Van den Kerkhof, Alfons; Thiéry, Régis

    2001-01-01

    The paper gives an overview of the phase relations in carbonic fluid inclusions with pure, binary and ternary mixtures of the system CO 2-CH 4-N 2, compositions, which are frequently found in geological materials. Phase transitions involving liquid, gas and solid phases in the temperature range between -192°C and 31°C are discussed and presented in phase diagrams ( PT, TX and VX projections). These diagrams can be applied for the interpretation of microthermometry data in order to determine fluid composition and molar volume (or density).

  10. Creep Rupture Life Prediction Based on Analysis of Large Creep Deformation

    Directory of Open Access Journals (Sweden)

    YE Wenming

    2016-08-01

    Full Text Available A creep rupture life prediction method for high temperature component was proposed. The method was based on a true stress-strain elastoplastic creep constitutive model and the large deformation finite element analysis method. This method firstly used the high-temperature tensile stress-strain curve expressed by true stress and strain and the creep curve to build materials' elastoplastic and creep constitutive model respectively, then used the large deformation finite element method to calculate the deformation response of high temperature component under a given load curve, finally the creep rupture life was determined according to the change trend of the responsive curve.The method was verified by durable test of TC11 titanium alloy notched specimens under 500 ℃, and was compared with the three creep rupture life prediction methods based on the small deformation analysis. Results show that the proposed method can accurately predict the high temperature creep response and long-term life of TC11 notched specimens, and the accuracy is better than that of the methods based on the average effective stress of notch ligament, the bone point stress and the fracture strain of the key point, which are all based on small deformation finite element analysis.

  11. [An optical-fiber-sensor-based spectrophotometer for soil non-metallic nutrient determination].

    Science.gov (United States)

    He, Dong-xian; Hu, Juan-xiu; Lu, Shao-kun; He, Hou-yong

    2012-01-01

    In order to achieve rapid, convenient and efficient soil nutrient determination in soil testing and fertilizer recommendation, a portable optical-fiber-sensor-based spectrophotometer including immersed fiber sensor, flat field holographic concave grating, and diode array detector was developed for soil non-metallic nutrient determination. According to national standard of ultraviolet and visible spectrophotometer with JJG 178-2007, the wavelength accuracy and repeatability, baseline stability, transmittance accuracy and repeatability measured by the prototype instrument were satisfied with the national standard of III level; minimum spectral bandwidth, noise and excursion, and stray light were satisfied with the national standard of IV level. Significant linear relationships with slope of closing to 1 were found between the soil available nutrient contents including soil nitrate nitrogen, ammonia nitrogen, available phosphorus, available sulfur, available boron, and organic matter measured by the prototype instrument compared with that measured by two commercial single-beam-based and dual-beam-based spectrophotometers. No significant differences were revealed from the above comparison data. Therefore, the optical-fiber-sensor-based spectrophotometer can be used for rapid soil non-metallic nutrient determination with a high accuracy.

  12. Solution behavior of hydrogen isotopes and other non-metallic elements in liquid lithium

    Energy Technology Data Exchange (ETDEWEB)

    Maroni, V.A.; Calaway, W.F.; Veleckis, E.; Yonco, R.M.

    1976-01-01

    Results of experimental studies to measure selected thermodynamic properties for systems of lithium with non-metallic elements are reported. Investigations of the Li-H, Li-D, and Li-T systems have led to the elucidation of the dilute solution behavior and the H/D/T isotope effects. In the case of the Li-H and Li-D systems, the principal features of the respective phase diagrams have been delineated. The solubility of Li-D in liquid lithium has been measured down to 200/sup 0/C. The solubility of Li/sub 3/N in liquid lithium and the thermal decomposition of Li/sub 3/N have also been studied. From these data, the free energy of formation of Li/sub 3/N and the Sieverts' constant for dissolution of nitrogen in lithium have been determined. Based on studies of the distribution of non-metallic elements between liquid lithium and selected molten salts, it appears that molten salt extraction offers promise as a means of removing these impurity elements (e.g., H, D, T, O, N, C) from liquid lithium.

  13. Bacterial assimilation reduction of iron in the treatment of non-metallics

    Directory of Open Access Journals (Sweden)

    Peter Malachovský

    2005-11-01

    Full Text Available Natural non-metallics, including granitoide and quartz sands, often contain iron which decreases the whiteness of these raw materials. Insoluble Fe3+ in these samples could be reduced to soluble Fe2+ by bacteria of Bacillus spp. and Saccharomyces spp. The leaching effect, observed by the measurement of Fe2+concentration in a solution, showed higher activities of a bacterial kind isolated from the Bajkal lake and also by using of yeast Saccharomyces sp. during bioleaching of quartz sands. However, allkinds of Bacillus spp. isolated from the Slovak deposit and from Bajkal lake were very active in the iron reduction during bioleaching of the feldspar raw material. This metal was efficiently removed from quartz sands as documented by the Fe2O3 decrease (from 0,317 % to 0,126 % and from feldpars raw materials by the Fe2O3 decrease (from 0,288 % to 0,115 % after bioleaching. The whiteness of these non-metallics was increased during a visual comparison of samples before and after bioleaching but samples contain selected magnetic particles. A removal of iron as well as a release of iron minerals from silicate matrix should increase the effect of the magnetic separation and should give a product which is suitable for industrial applications.

  14. PVC-based composite material containing recycled non-metallic printed circuit board (PCB) powders.

    Science.gov (United States)

    Wang, Xinjie; Guo, Yuwen; Liu, Jingyang; Qiao, Qi; Liang, Jijun

    2010-12-01

    The study is directed to the use of non-metallic powders obtained from comminuted recycled paper-based printed circuit boards (PCBs) as an additive to polyvinyl chloride (PVC) substrate. The physical properties of the non-metallic PCB (NMPCB) powders were measured, and the morphological, mechanical and thermal properties of the NMPCB/PVC composite material were investigated. The results show that recycled NMPCB powders, when added below a threshold, tended to increase the tensile strength and bending strength of PVC. When 20 wt% NMPCB powders (relative to the substrate PVC) of an average diameter of 0.08 mm were added, the composite tensile strength and bending strength reached 22.6 MPa and 39.83 MPa, respectively, representing 107.2% and 123.1% improvement over pure PVC. The elongation at break of the composite material reached 151.94% of that of pure PVC, while the Vicat softening temperature of the composite material did not increase significantly compared to the pure PVC. The above results suggest that paper-based NMPCB powders, when used at appropriate amounts, can be effective for toughening PVC. Thus, this study suggests a new route for reusing paper-based NMPCB, which may have a significant beneficial environmental impact.

  15. A Fully Non-Metallic Gas Turbine Engine Enabled by Additive Manufacturing

    Science.gov (United States)

    Grady, Joseph E.; Halbig, Michael C.; Singh, Mrityunjay

    2015-01-01

    In a NASA Aeronautics Research Institute (NARI) sponsored program entitled "A Fully Non-Metallic Gas Turbine Engine Enabled by Additive Manufacturing", evaluation of emerging materials and additive manufacturing technologies was carried out. These technologies may enable fully non-metallic gas turbine engines in the future. This paper highlights the results of engine system trade studies which were carried out to estimate reduction in engine emissions and fuel burn enabled due to advanced materials and manufacturing processes. A number of key engine components were identified in which advanced materials and additive manufacturing processes would provide the most significant benefits to engine operation. In addition, feasibility of using additive manufacturing technologies to fabricate gas turbine engine components from polymer and ceramic matrix composite were demonstrated. A wide variety of prototype components (inlet guide vanes (IGV), acoustic liners, engine access door) were additively manufactured using high temperature polymer materials. Ceramic matrix composite components included first stage nozzle segments and high pressure turbine nozzle segments for a cooled doublet vane. In addition, IGVs and acoustic liners were tested in simulated engine conditions in test rigs. The test results are reported and discussed in detail.

  16. Creep motion of a model frictional system

    CERN Document Server

    Blanc, Baptiste; Géminard, Jean-Christophe

    2011-01-01

    We report on the dynamics of a model frictional system submitted to minute external perturbations. The system consists of a chain of sliders connected through elastic springs that rest on an incline. By introducing cyclic expansions and contractions of the springs we observe a reptation of the chain. We account for the average reptation velocity theoretically. The velocity of small systems exhibits a series of plateaus as a function of the incline angle. Due to elastic e ects, there exists a critical amplitude below which the reptation is expected to cease. However, rather than a full stop of the creep, we observe in numerical simulations a transition between a continuous-creep and an irregular-creep regime when the critical amplitude is approached. The latter transition is reminiscent of the transition between the continuous and the irregular compaction of granular matter submitted to periodic temperature changes.

  17. Transitional Thermal Creep of Early Age Concrete

    DEFF Research Database (Denmark)

    Hauggaard-Nielsen, Anders Boe; Damkilde, Lars; Freiesleben Hansen, Per

    1999-01-01

    Couplings between creep of hardened concrete and temperature/water effects are well-known. Both the level and the gradients in time of temperature or water content influence the creep properties. In early age concrete the internal drying and the heat development due to hydration increase the effect...... of these couplings. The purpose of this work is to set up a mathematical model for creep of concrete which includes the transitional thermal effect. The model govern both early age concrete and hardened concrete. The development of the material properties in the model are assumed to depend on the hydration process...... and the thermal activation of the water in the microstructure. The thermal activation is assumed to be governed by the Arrhenius principle and the activation energy of the viscosity of water is found applicable in the analysis of experimental data. Changes in temperature create an imbalance in the microstructure...

  18. Transitional Thermal Creep of Early Age Concrete

    DEFF Research Database (Denmark)

    Hauggaard, A. B.; Damkilde, L.; Hansen, Per Freiesleben

    1999-01-01

    Couplings between creep of hardened concrete and temperature/water effects are well-known. Both the level and the gradients in time of temperature or water content influence the creep properties. In early age concrete the internal drying and the heat development due to hydration increase the effect...... of these couplings. The purpose of this work is to set up a mathematical model for creep of concrete that includes the transitional thermal effect. The model governs both early age concrete and hardened concrete. The development of the material properties in the model is assumed to depend on the hydration process...... and the thermal activation of water in the microstructure. The thermal activation is assumed to be governed by the Arrhenius principle, and the activation energy of the viscosity of water is found applicable in the analysis of the experimental data. Changes in temperature create an imbalance in the microstructure...

  19. Creep Effects in Pultruded FRP Beams

    Science.gov (United States)

    Boscato, G.; Casalegno, C.; Russo, S.

    2016-03-01

    The paper presents results of two creep tests on pultruded open-section GFRP beams aimed to evaluate the long-term deformations, the residual deflection after unloading, and the influence of creep strains on the flexuraltorsional buckling phenomenon. Two beams were subjected to a constant load for about one year. Then one of the beams was unloaded to evaluate its residual deflection. For the other beam, the load was increased up to failure, and the residual buckling strength was compared with that of a similar beam tested up to failure. The parameters of the Findley power law are evaluated, and the experimental results are compared with those of numerical analyses and with available formulations for prediction of the time-dependent properties of composite beams. Results of the investigation testify, in particular, to a noninsignificant time-dependent increment in deflections of the beams and to a significant reduction in their buckling strength due to creep deformations.

  20. Measurement of local creep properties in stainless steel welds

    OpenAIRE

    Sakanashi, Y.; Gungor, S; Bouchard, J.

    2012-01-01

    A high temperature measurement system for creep deformation based on the digital image correlation (DIC) technique is described. The new system is applied to study the behaviour of a multi-pass welded joint in a high temperature tensile test and a load controlled creep test at 545°C. Spatially resolved tensile properties and time dependent creep deformation properties across a thick section type 316 stainless steel multi-pass welded joint are presented and discussed. Significantly lower creep...

  1. Nanoindentation investigation of creep properties of calcium silicate hydrates

    OpenAIRE

    Vandamme, Matthieu; ULM, Franz Josef

    2013-01-01

    The creep properties of calcium silicate hydrates (C-S-H) are assessed by means of nanoindentation creep experiments on a wide range of substoichiometric cement pastes. We observe that, after a few seconds, the measured creep compliance of C-S-H is very well captured by a logarithmic time function. The rate of the logarithmic creep is found to scale in a unique manner with indentation modulus, indentation hardness, and packing density, independent of processing, mix proportions, indenter geom...

  2. Recommendation for Creep and Creep-fatigue assessment for P91 Components

    OpenAIRE

    Pohja, Rami; HOLMSTROM BJORN; LEE Hyeong-Yeon

    2015-01-01

    This report is based on the results and experience gained in assessing both public domain and MATTER data, some previously reported in the MATTER deliverable D4.5: “Creep-fatigue interaction rules for P91” and some assessed here. A number of methods, including interaction diagram based methods and simplified methods, have been compared for predicting the creep-fatigue life of P91 steel. The effect of cyclic softening on creep properties have been considered in the evaluations presented in thi...

  3. Modelling of creep damage development in ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Sandstroem, R. [Swedish Institute for Metals Research, Stockholm (Sweden)

    1998-12-31

    The physical creep damage, which is observed in fossil-fired power plants, is mainly due to the formation of cavities and their interaction. It has previously been demonstrated that both the nucleation and growth of creep cavities can be described by power functions in strain for low alloy and 12 % CrMoV creep resistant steels. It possible to show that the physical creep damage is proportional to the product of the number of cavities and their area. Hence, the physical creep damage can also be expressed in terms of the creep strain. In the presentation this physical creep damage is connected to the empirical creep damage classes (1-5). A creep strain-time function, which is known to be applicable to low alloy and 12 % CrMoV creep resistant steels, is used to describe tertiary creep. With this creep strain - time model the residual lifetime can be predicted from the observed damage. For a given damage class the remaining life is directly proportional to the service time. An expression for the time to the next inspection is proposed. This expression is a function of fraction of the total allowed damage, which is consumed till the next inspection. (orig.) 10 refs.

  4. Micromechanical studies of cyclic creep fracture under stress controlled loading

    DEFF Research Database (Denmark)

    van der Giessen, Erik; Tvergaard, Viggo

    1996-01-01

    This paper deals with a study of intergranular failure by creep cavitation under stress-controlled cyclic loading conditions. Loading is assumed to be slow enough that diffusion and creep mechanisms (including grain boundary sliding) dominate, leading to intergranular creep fracture. This study i...

  5. The Creep Properties of Fine Sandstone under Uniaxial Tensile Stress

    Directory of Open Access Journals (Sweden)

    Jiang Haifei

    2015-09-01

    Full Text Available A graduated uniaxial direct tensile creep test for fine sandstone is conducted by adopting a custom-designed direct tensile test device for rock. The experiment shows that the tensile creep of fine sandstone has similar creep curve patterns to those of compression creep, while the ratios of the creep strain to the total strain obtained in the tensile tests are substantially higher than those obtained for similar compression tests, which indicates that the creep ability of rock in the tensile process is higher than that in the uniaxial compression process. Based on the elastic modulus in the approximately linear portion of the obtained isochronous stress-strain curves of the tensile creep, the time dependence of the elasticity modulus for the Kelvin model is evaluated, and a revised generalized Kelvin model is obtained by substitution into the generalized Kelvin model. A new viscousplastic model is proposed to describe the accelerated creep properties, and this model is combined in series with the revised generalized Kelvin model to form a new nonlinear viscoelastic-plastic creep model that can describe the properties of attenuation creep, steady creep, and accelerated creep. Comparison of the test and theoretical curves demonstrates that they are nearly identical, which verifies the performance of the model.

  6. Micromechanical studies of cyclic creep fracture under stress- controlled loading

    NARCIS (Netherlands)

    Giessen, E. van der; Tvergaard, V.

    1996-01-01

    This paper deals with a study of intergranular failure by creep cavitation under stress-controlled cyclic loading conditions. Loading is assumed to be slow enough that diffusion and creep mechanisms (including grain boundary sliding) dominate, leading to intergranular creep fracture. This study is

  7. New constitutive model for the study of creeping solids

    Institute of Scientific and Technical Information of China (English)

    王世文; 杨兆建; 冯建玲

    2002-01-01

    In this paper, a incremental form of constitutive laws for creeping studies are proposed. The equations are based on the concept of creep hardening surface. Damage effects were introduced to the new constitutive relations to study solids creeping effects with pre-existing damages. The present formula is easy to be adopted into other numerical procedures such as finite element methods.

  8. Nanoindentation creep versus bulk compressive creep of dental resin-composites.

    Science.gov (United States)

    El-Safty, S; Silikas, N; Akhtar, R; Watts, D C

    2012-11-01

    To evaluate nanoindentation as an experimental tool for characterizing the viscoelastic time-dependent creep of resin-composites and to compare the resulting parameters with those obtained by bulk compressive creep. Ten dental resin-composites: five conventional, three bulk-fill and two flowable were investigated using both nanoindentation creep and bulk compressive creep methods. For nano creep, disc specimens (15mm×2mm) were prepared from each material by first injecting the resin-composite paste into metallic molds. Specimens were irradiated from top and bottom surfaces in multiple overlapping points to ensure optimal polymerization using a visible light curing unit with output irradiance of 650mW/cm(2). Specimens then were mounted in 3cm diameter phenolic ring forms and embedded in a self-curing polystyrene resin. Following grinding and polishing, specimens were stored in distilled water at 37°C for 24h. Using an Agilent Technologies XP nanoindenter equipped with a Berkovich diamond tip (100nm radius), the nano creep was measured at a maximum load of 10mN and the creep recovery was determined when each specimen was unloaded to 1mN. For bulk compressive creep, stainless steel split molds (4mm×6mm) were used to prepare cylindrical specimens which were thoroughly irradiated at 650mW/cm(2) from multiple directions and stored in distilled water at 37°C for 24h. Specimens were loaded (20MPa) for 2h and unloaded for 2h. One-way ANOVA, Levene's test for homogeneity of variance and the Bonferroni post hoc test (all at p≤0.05), plus regression plots, were used for statistical analysis. Dependent on the type of resin-composite material and the loading/unloading parameters, nanoindentation creep ranged from 29.58nm to 90.99nm and permanent set ranged from 8.96nm to 30.65nm. Bulk compressive creep ranged from 0.47% to 1.24% and permanent set ranged from 0.09% to 0.38%. There was a significant (p=0.001) strong positive non-linear correlation (r(2)=0.97) between bulk

  9. Low Temperature Creep of Hot-Extruded Near-Stoichiometric NiTi Shape Memory Alloy. Part I; Isothermal Creep

    Science.gov (United States)

    Raj, S. V.; Noebe, R. D.

    2013-01-01

    This two-part paper is the first published report on the long term, low temperature creep of hot-extruded near-stoichiometric NiTi. Constant load tensile creep tests were conducted on hot-extruded near-stoichiometric NiTi at 300, 373 and 473 K under initial applied stresses varying between 200 and 350 MPa as long as 15 months. These temperatures corresponded to the martensitic, two-phase and austenitic phase regions, respectively. Normal primary creep lasting several months was observed under all conditions indicating dislocation activity. Although steady-state creep was not observed under these conditions, the estimated creep rates varied between 10(exp -10) and 10(exp -9)/s. The creep behavior of the two phases showed significant differences. The martensitic phase exhibited a large strain on loading followed by a primary creep region accumulating a small amount of strain over a period of several months. The loading strain was attributed to the detwinning of the martensitic phase whereas the subsequent strain accumulation was attributed to dislocation glide-controlled creep. An "incubation period" was observed before the occurrence of detwinning. In contrast, the austenitic phase exhibited a relatively smaller loading strain followed by a primary creep region, where the creep strain continued to increase over several months. It is concluded that the creep of the austenitic phase occurs by a dislocation glide-controlled creep mechanism as well as by the nucleation and growth of deformation twins.

  10. Inclusive Education in China

    Institute of Scientific and Technical Information of China (English)

    杨永芳

    2005-01-01

    This paper is concerned about inclusive education in China,which is exemplified bythe following aspects:creating inclusive culture,producing inclusive policies and evolving inclusivepractice.Also,problems related to the inclusion are identified in this paper.

  11. A study of many-body phenomena in metal nanoclusters (Au, Cu) close to their transition to the nonmetallic state

    NARCIS (Netherlands)

    Borman, VD; Borisyuk, PV; Lebid'ko, VV; Pushkin, AA; Tronin, VN; Troyan, [No Value; Antonov, DA; Filatov, DO

    2006-01-01

    The results of a study of many-body phenomena in gold and copper nanoclusters are presented. The measured conductivity as a function of nanocluster height h was found to have a minimum at h approximate to 0.6 nm. Conductivity was local in character at nanocluster sizes l infinity) to nonmetallic (ep

  12. Creep and creep-fatigue behavior of high chromium steel weldment

    Institute of Scientific and Technical Information of China (English)

    Yukio TAKAHASHI; Masaaki TABUCHI

    2011-01-01

    Manuscript received I December 2010; in revised form 9 March 2011Strength of welded joints of high chromium steels is one of the important concerns for fabricators and operators of ultra supercritical thermal power plants. A number of creep as well as creep-fatigue tests with tensile hold have been carried out on the welded joints of two types of high chromium steels widely used in Japan, I.e. Grade 91 and 122 steels. It was found that failure occurred in fine grain heat-affected zone in all the creep-fatigue tests, even at a relatively low temperature and fairly short time where failure occurred in plain base metal region in simple creep testing. Four procedures were used to predict failure lives and their results were compared with the test results. A newly proposed energy-based approach gave the best estimation of failure life, without respect of the material and temperature.

  13. Renewal theory applied to creep and inelastic behavior of copper

    Energy Technology Data Exchange (ETDEWEB)

    Gibbons, K.A.; Cook, D.E. [Wright-Patterson Air Force Base, Dayton, OH (United States); Bearden, K.L. [Air Force Academy, Colorado Springs, CO (United States)

    1995-12-31

    A series of constant load creep tests on C11000 copper are described. The copper microstructure was closely controlled through appropriate heat treatment. Renewal theory was applied to interpret creep test data while developing the parameters of a general inelasticity model suitable for prediction. Creep experiments were predicted using renewal theory. Time varying load and load control stress-strain experiments were also predicted using renewal inelasticity theory. Results show that renewal theory is an efficient and effective approach to modeling creep of copper, needing a limited number of parameters. The simplicity of applying this theory to creep, variable load conditions, and a stress-strain experiment predictions for copper has been demonstrated.

  14. Creep rupture behavior of welded Grade 91 steel

    Energy Technology Data Exchange (ETDEWEB)

    Shrestha, Triratna [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Basirat, Mehdi [Department of Mechanical Engineering, University of Idaho, Moscow, ID 83844 (United States); Alsagabi, Sultan; Sittiho, Anumat [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Charit, Indrajit, E-mail: icharit@uidaho.edu [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Potirniche, Gabriel P. [Department of Mechanical Engineering, University of Idaho, Moscow, ID 83844 (United States)

    2016-07-04

    Creep rupture behavior of fusion welded Grade 91 steel was studied in the temperature range of 600 – 700 °C and at stresses of 50–200 MPa. The creep data were analyzed in terms of the Monkman-Grant relation and Larson-Miller parameter. The creep damage tolerance factor was used to identify the origin of creep damage. The creep damage was identified as the void growth in combination with microstructural degradation. The fracture surface morphology of the ruptured specimens was studied by scanning electron microscopy and deformed microstructure examined by transmission electron microscopy, to further elucidate the rupture mechanisms.

  15. Creep properties and microstructure of the new wrought austenitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Vlasak, T.; Hakl, J.; Novak, P. [SVUM a.s., Prague (Czech Republic); Vyrostkova, A. [Slovak Academy of Sciences, Kosice (Slovakia). Inst. of Materials Research

    2010-07-01

    The contribution is oriented on the new wrought austenitic steel BGA4 (Cr23Ni15Mn6Cu3W1.5NbVMo) developed by the British Corus Company. Our main aim is to present creep properties studied in SVUM a.s. Prague during COST 536 programme. The dependencies of the creep strength, strength for specific creep strain and minimum creep strain rate were evaluated on the basis of long term creep tests carried out at temperature interval (625; 725) C. Important part of a paper is metallographic analysis. (orig.)

  16. Steady-state creep in the mantle

    Directory of Open Access Journals (Sweden)

    G. RANALLI

    1977-06-01

    Full Text Available SUMMARY - The creep equations for steady-state flow of olivine at high
    pressure and temperature are compared in an attempt to elucidate the rheological
    behaviour of the mantle. Results are presented in terms of applied deformation
    maps and curves of effective viscosity v depth.
    In the upper mantle, the transition stress between dislocation and diffusion
    creep is between 10 to 102 bar (as orders of magnitude for grain sizes from
    0.01 to 1 cm. The asthenosphere under continents is deeper, and has higher
    viscosity, than under oceans. Predominance of one creep mechanism above the
    others depends on grain size, strain rate, and volume fraction of melt; the
    rheological response can be different for different geodynamic processes.
    In the lower mantle, on the other hand, dislocation creep is predominant
    at all realistic grain sizes and strain rates. If the effective viscosity has to be only
    slightly higher than in the upper mantle, as some interpretations of glacioisostatic
    rebound suggest, then the activation volume cannot be larger than
    11 cm3 mole^1.

  17. Creep measurements on curing epoxy systems

    DEFF Research Database (Denmark)

    Kammer, Charlotte; Szabo, Peter

    1998-01-01

    The chemical curing of a stoichiometric mixture of the diglycidyl ether of bisphenol A and a 1,3-bis-(aminomethyl)-cyclohexane is studied.Creep experiments are combined with measurements in a Differential Scanning Calorimeter (DSC) to determine the change in bulk viscosity due to network formation....

  18. First principles model of carbonate compaction creep

    Science.gov (United States)

    Keszthelyi, Daniel; Dysthe, Dag Kristian; Jamtveit, Bjørn

    2016-05-01

    Rocks under compressional stress conditions are subject to long-term creep deformation. From first principles we develop a simple micromechanical model of creep in rocks under compressional stress that combines microscopic fracturing and pressure solution. This model was then upscaled by a statistical mechanical approach to predict strain rate at core and reservoir scale. The model uses no fitting parameter and has few input parameters: effective stress, temperature, water saturation porosity, and material parameters. Material parameters are porosity, pore size distribution, Young's modulus, interfacial energy of wet calcite, the dissolution, and precipitation rates of calcite, and the diffusion rate of calcium carbonate, all of which are independently measurable without performing any type of deformation or creep test. Existing long-term creep experiments were used to test the model which successfully predicts the magnitude of the resulting strain rate under very different effective stress, temperature, and water saturation conditions. The model was used to predict the observed compaction of a producing chalk reservoir.

  19. Irreversible thermodynamics of creep in crystalline solids

    Science.gov (United States)

    Mishin, Y.; Warren, J. A.; Sekerka, R. F.; Boettinger, W. J.

    2013-11-01

    We develop an irreversible thermodynamics framework for the description of creep deformation in crystalline solids by mechanisms that involve vacancy diffusion and lattice site generation and annihilation. The material undergoing the creep deformation is treated as a nonhydrostatically stressed multicomponent solid medium with nonconserved lattice sites and inhomogeneities handled by employing gradient thermodynamics. Phase fields describe microstructure evolution, which gives rise to redistribution of vacancy sinks and sources in the material during the creep process. We derive a general expression for the entropy production rate and use it to identify of the relevant fluxes and driving forces and to formulate phenomenological relations among them taking into account symmetry properties of the material. As a simple application, we analyze a one-dimensional model of a bicrystal in which the grain boundary acts as a sink and source of vacancies. The kinetic equations of the model describe a creep deformation process accompanied by grain boundary migration and relative rigid translations of the grains. They also demonstrate the effect of grain boundary migration induced by a vacancy concentration gradient across the boundary.

  20. Creep measurements on curing epoxy systems

    DEFF Research Database (Denmark)

    Kammer, Charlotte; Szabo, Peter

    1998-01-01

    The chemical curing of a stoichiometric mixture of the diglycidyl ether of bisphenol A and a 1,3-bis-(aminomethyl)-cyclohexane is studied.Creep experiments are combined with measurements in a Differential Scanning Calorimeter (DSC) to determine the change in bulk viscosity due to network formation....

  1. Creep of granulated loose-fill insulation

    DEFF Research Database (Denmark)

    Rasmussen, Torben Valdbjørn

    with SP-Building Physics in Sweden and VTT Building Technology in Finland. For the round robin test a cellulosic fibre insulation material was used. The proposed standardised method for creep tests and theories are limited to cases when the granulated loose-fill material is exposed to a constant...

  2. Time constant of logarithmic creep and relaxation

    CSIR Research Space (South Africa)

    Nabarro, FRN

    2001-07-15

    Full Text Available of logarithmic creep have been proposed, the work-hardening of a set of barriers to dislocation motion, all having the same activation energy, or the progressive exhaustion of the weaker barriers in a set which has a distribution of activation energies...

  3. Influence of the Inclusion Shape on the Rolling Contact Fatigue Life of Carburized Steels

    Science.gov (United States)

    Neishi, Yutaka; Makino, Taizo; Matsui, Naoki; Matsumoto, Hitoshi; Higashida, Masashi; Ambai, Hidetaka

    2013-05-01

    It has been well known that the flaking failure in rolling contact fatigue (RCF) originates from nonmetallic inclusions in steels, and their apparent size is one of the important factors affecting RCF life. However, the influence of inclusion shape on the RCF life has not been fully clarified. In this study, attention was paid to the influence of the inclusion shape on the RCF life. This was evaluated by using carburized JIS-SCM420 (SAE4320) steels that contained two different shapes of MnS—stringer type and spheroidized type—as inclusions. Sectional observations were made to investigate the relation between the occurrence of shear crack in the subsurface and the shape of MnS. It was found that the RCF life was well correlated with the length of MnS projected to the load axis, and the initiation of shear crack in subsurface was accelerated as the length of MnS increased.

  4. A Novel Method for the Prediction of Critical Inclusion Size Leading to Fatigue Failure

    Science.gov (United States)

    Saberifar, S.; Mashreghi, A. R.

    2012-06-01

    The fatigue behavior of two commercial 30MnVS6 steels with similar microstructure and mechanical properties containing inclusions of different sizes were studied in the 107 cycles fatigue regime. The scanning electron microscopy (SEM) investigations of the fracture surfaces revealed that the nonmetallic inclusions are the main sources of fatigue crack initiation. Calculated according to the Murakami's model, the stress intensity factors were found to be suitable for the assessment of fatigue behavior. In this article, a new method is proposed for the prediction of the critical inclusion size, using Murakami's model. According to this method, a critical stress intensity factor was determined for the estimation of the critical inclusion size causing the fatigue failure.

  5. Mechanism of removing inclusions from molten aluminum by stirring active molten flux

    Institute of Scientific and Technical Information of China (English)

    周鸣; 李克; 孙宝德; 疏达; 倪红军; 王俊; 张佼

    2003-01-01

    Removal of inclusions from industrial pure molten aluminum(A01) by stirring active molten flux wasstudied. Wettability of nonmetallic inclusions in the molten aluminum was worse than that in active molten flux. Ac-cording to the surface renewal model, the inclusions were easily transferred into molten active flux from fine alumi-num droplets and then reacted chemically when molten aluminum was dispersed into fine aluminum droplets in stir-ring active molten flux. Tensile tests show that tensile strength of purified tensile sample(as-cast) increases by8.59%. SEM photographs show that the fracture cracks of purified tensile sample are homogeneous, and the dim-ples are small and homogeneous. From metallographs and statistic results of Leco analysis software, it is found thatthe quantities and sizes of the inclusions in purified sample are obviously fewer and smaller than in unpurified tensilesample(as-cast).

  6. Creep and creep rupture of fiber reinforced polymers: Long term variability

    Science.gov (United States)

    Jensen, Eric M.

    Fiber reinforced polymers continue to be used in ever increasing quantities for large weight critical structures which are designed to be in service for decades. Catastrophic failure of these structures can have dire consequences. Therefore, long term creep and creep rupture predictions are of critical importance. To this end, a multiscale creep rupture model based on the kinetic concept of strength is developed to predict failure. A linkage between damage evolution and the apparent modulus degradation is proposed, which allows for the prediction of creep strain. This combined creep strain and creep rupture model is implemented in a progressive failure user subroutine for finite element software. Model calibration experiments were conducted on Panex 35/M9.7 material system. Combining structural quantification, full field strain measurements and finite element simulations, mechanisms behind material variability and scatter have been identified and modeled resulting in improved life predictions. The material data collected and a video of the two-dimensional strain evolution during a transverse load and unload test have been provided as supplemental materials.

  7. Creep properties of aged duplex stainless steels containing [sigma] phase

    Energy Technology Data Exchange (ETDEWEB)

    Shek, C.H.; Wong, K.W.; Lai, J.K.L. (City Univ. of Hong Kong, Kowloon (Hong Kong). Dept. of Physics and Materials Science); Li, D.J. (Department of Materials Engineering, Dalian University of Technology, Dalian 116 024 (China))

    1999-06-30

    The creep properties of a cast of duplex stainless steel were characterized at temperatures 550-800 C under different loading conditions. For fully aged specimens containing [sigma], the stress exponent for creep was close to 3 and the activation energy was 281[+-]9 kJ mol[sup -1]. The results suggested that the creep mechanism in the samples in this investigation was controlled by dislocation movement. Extensive [sigma]/[gamma][sub 2] interfaces introduced during ageing improved the creep resistance of the material and related to a reduction of the creep rate in Stage II creep and an increase in the creep rupture strength of the material. Microstructural studies revealed the dependence of the creep properties on the morphology of the microstructure. Among the aged specimens containing [sigma], the creep strength and ductility were higher for specimens having larger [gamma] grain thickness measured on the longitudinal plane. This characteristic was related to the crack propagation and interconnection of voids within [gamma] matrix during tertiary creep. With appropriate solution treatment, the creep strength of [sigma]-containing steels can be improved to a value exceeding that of type 316 steels. (orig.) 14 refs.

  8. The creep experiment and theoretical model analysis of gascontaining coal

    Institute of Scientific and Technical Information of China (English)

    YIN Guang-zhi; ZHANG Dong-ming; WANG Wei-zhong

    2007-01-01

    A creep experiment of preformed molding coal under different confining pressures were carried out using self-developed 3-triaxial creep loading device for gas-containing coal, which loaded by Shimadzu AGI-250 kN electrical servo-controlled stiffness testing machine. Based on the experimental results, the variation trend of axial deformation under different stress states was studied, and creep failure characteristics of gascontaining coal under different confining pressures were analyzed. The experimental results were identified with seven-component nonlinear viscoelasto-plastic creep model (Hohai model), and the creep material parameters were obtained. The experimental result complies well with the theoretical value of this model. It indicates that creep constitutive relation of gas-containing coal can be expressed by nonlinear viscoelasto-plastic creep model correctly.

  9. An Overview of Irradiation Creep of Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Woo Seog [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    This paper reviewed systematically a state-of-art of irradiation creep for stainless steels to provide a background information for performing irradiation creep tests and establishing the creep model for advanced domestic steels effectively. An irradiation creep model of SFR core materials is necessary to apply to the fuel cladding and assembly materials of domestic SFR reactor system. The document of in-reactor irradiation creep has been obtained by investing a long time and large-scale cost using limited experimental research reactors. This paper will provide the knowledge to understand the irradiation creep and to obtain the background information of advanced domestic steels, so that it hopes to practically apply for timely producing the documents of irradiation creep of advanced domestic steels necessary for the national SFR program.

  10. Soil creep and historic landscape changes

    Science.gov (United States)

    Lucke, Bernhard

    2017-04-01

    Many erosion models assume that soil sediments are transported grain-by-grain, and thus calculate loss and deposition according to parameters such as bulk density and average grain size. However, clay-rich soils, such as the widespread Red Mediterranean Soils or Terrae Rossae that are often found near important archaeological sites, can behave differently. This is illustrated by a case study of historic landscape changes in Jordan, where evidence for soil creep as main process of soil movement was found in the context of ancient cemeteries. Due to a dominance of smectites, the Red Mediterranean Soils in this area shrink and form cracks during the dry period. Because of the cracks and underlying limestone karst, they can swallow strong rains without high erosion risk. However, when water-saturated, these soils expand and can start creeping. Buried geoarchaeological features like small water channels on formerly cleared rocks suggest that soils can move a few cm uplslope when wet, and buried graves illustrate that soil creep can create new level surfaces, sealing cavities but not completely filling them. Such processes seem associated with slumping and earth flows as instable rocks might collapse under the weight of a creeping soil. While it is very difficult to measure such processes, landscape archaeology offers at least an indirect approach that could be suited to estimate the scale and impact of soil creep. Analogies with modern rainfalls, including record levels of precipitation during the winter 1991/1992, indicate that similar levels of soil moisture have not been reached during times of modern instrumental rainfall monitoring. This suggests that very strong deluges must have occurred during historical periods, that could potentially cause tremendous damage to modern infrastructure if happening again.

  11. The Impact of Weld Metal Creep Strength on the Overall Creep Strength of 9% Cr Steel Weldments

    OpenAIRE

    Mayr, Peter; Mitsche, Stefan; Cerjak, Horst; Allen, Samuel Miller

    2010-01-01

    In this work, three joints of a X11CrMoWVNb9-1-1 (P911) pipe were welded with three filler metals by conventional arc welding. The filler metals varied in creep strength level, so that one overmatched, one undermatched, and one matched the creep strength of the P911 grade pipe base material. The long-term objective of this work was to study the influence of weld metal creep strength on the overall creep behavior of the welded joints and their failure mechanism. Uniaxial creep tests at 600°C a...

  12. Calculating the Carrying Capacity of Flexural Prestressed Concrete Beams with Non-Metallic Reinforcement

    Directory of Open Access Journals (Sweden)

    Mantas Atutis

    2011-04-01

    Full Text Available The article reviews moment resistance design methods of prestressed concrete beams with fibre-reinforced polymer (FRP reinforcement. FRP tendons exhibit linear elastic response to rupture without yielding and thus failure is expected to be brittle. The structural behaviour of beams prestressed with FRP tendons is different from beams with traditional steel reinforcement. Depending on the reinforcement ratio, the flexural behaviour of the beam can be divided into several groups. The numerical results show that depending on the nature of the element failure, moment resistance calculation results are different by using reviewed methods. It was found, that the use of non-metallic reinforcement in prestressed concrete structures is effective: moment capacity is about 5% higher than that of the beams with conventional steel reinforcement.Article in Lithuanian

  13. Capacitance probe for detection of anomalies in non-metallic plastic pipe

    Science.gov (United States)

    Mathur, Mahendra P.; Spenik, James L.; Condon, Christopher M.; Anderson, Rodney; Driscoll, Daniel J.; Fincham, Jr., William L.; Monazam, Esmail R.

    2010-11-23

    The disclosure relates to analysis of materials using a capacitive sensor to detect anomalies through comparison of measured capacitances. The capacitive sensor is used in conjunction with a capacitance measurement device, a location device, and a processor in order to generate a capacitance versus location output which may be inspected for the detection and localization of anomalies within the material under test. The components may be carried as payload on an inspection vehicle which may traverse through a pipe interior, allowing evaluation of nonmetallic or plastic pipes when the piping exterior is not accessible. In an embodiment, supporting components are solid-state devices powered by a low voltage on-board power supply, providing for use in environments where voltage levels may be restricted.

  14. Ambipolar surface state transport in nonmetallic stoichiometric Bi2Se3 crystals

    Science.gov (United States)

    Syers, Paul; Paglione, Johnpierre

    2017-01-01

    Achieving true bulk insulating behavior in Bi2Se3 , the archetypal topological insulator with a simplistic one-band electronic structure and sizable band gap, has been prohibited by a well-known self-doping effect caused by selenium vacancies, whose extra electrons shift the chemical potential into the bulk conduction band. We report a synthesis method for achieving stoichiometric Bi2Se3 crystals that exhibit nonmetallic behavior in electrical transport down to low temperatures. Hall-effect measurements indicate the presence of both electron- and holelike carriers, with the latter identified with surface state conduction and the achievement of ambipolar transport in bulk Bi2Se3 crystals without gating techniques. With carrier mobilities surpassing the highest values yet reported for topological surface states in this material, the achievement of ambipolar transport via upward band bending is found to provide a key method to advancing the potential of this material for future study and applications.

  15. Combined nonmetallic electronegativity equalisation and point-dipole interaction model for the frequency-dependent polarisability

    Science.gov (United States)

    Smalø, Hans S.; Åstrand, Per-Olof; Mayer, Alexandre

    2013-07-01

    A molecular mechanics model for the frequency-dependent polarisability is presented. It is a combination of a recent model for the frequency dependence in a charge-dipole model [Nanotechnology 19, 025203, 2008] and a nonmetallic modification of the electronegativity equalisation model rephrased as atom-atom charge-transfer terms [J. Chem. Phys. 131, 044101, 2009]. An accurate model for the frequency-dependent polarisability requires a more accurate partitioning into charge and dipole contributions than the static polarisability, which has resulted in several modifications of the charge-transfer model. Results are presented for hydrocarbons, including among others, alkanes, polyenes and aromatic systems. Although their responses to an electric field are quite different in terms of the importance of charge-transfer contributions, it is demonstrated that their frequency-dependent polarisabilities can be described with the same model and the same set of atom-type parameters.

  16. Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon

    Science.gov (United States)

    Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

    2014-10-01

    The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65 mV, an apparent exchange current density of 5.7 × 10-2 mA cm-2 and a high hydrogen production rate of 20.8 mL cm-2 h-1 at -0.35 V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density.

  17. Modelling of degradation processes in creep resistant steels through accelerated creep tests after long-term isothermal ageing

    Energy Technology Data Exchange (ETDEWEB)

    Sklenicka, V.; Kucharova, K.; Svoboda, M.; Kroupa, A.; Kloc, L. [Academy of Sciences of the Czech Republic, Brno (Czech Republic). Inst. of Physics of Materials; Cmakal, J. [UJP PRAHA a.s., Praha-Zbraslav (Czech Republic)

    2010-07-01

    Creep behaviour and degradation of creep properties of creep resistant materials are phenomena of major practical relevance, often limiting the lives of components and structures designed to operate for long periods under stress at elevated and/or high temperatures. Since life expectancy is, in reality, based on the ability of the material to retain its high-temperature creep strength for the projected designed life, methods of creep properties assessment based on microstructural evolution in the material during creep rather than simple parametric extrapolation of short-term creep tests are necessary. In this paper we will try to further clarify the creep-strength degradation of selected advanced creep resistant steels. In order to accelerate some microstructural changes and thus to simulate degradation processes in long-term service, isothermal ageing at 650 C for 10 000 h was applied to P91 and P23 steels in their as-received states. The accelerated tensile creep tests were performed at temperature 600 C in argon atmosphere on all steels both in the as-received state and after long-term isothermal ageing, in an effort to obtain a more complete description of the role of microstructural stability in high temperature creep of these steels. Creep tests were followed by microstructural investigations by means of both transmission and scanning electron microscopy and by the thermodynamic calculations. The applicability of the accelerated creep tests was verified by the theoretical modelling of the phase equilibria at different temperatures. It is suggested that under restructed oxidation due to argon atmosphere microstructural instability is the main detrimental process in the long-term degradation of the creep rupture strength of these steels. (orig.)

  18. Development of a probabilistic model for the prediction of fatigue life in the very high cycle fatigue (VHCF range based on inclusion population

    Directory of Open Access Journals (Sweden)

    Kolyshkin A.

    2014-06-01

    Full Text Available The VHCF behaviour of metallic materials containing microstructural defects such as non-metallic inclusions is determined by the size and distribution of the damage dominating defects. In the present paper, the size and location of about 60.000 inclusions measured on the longitudinal and transversal cross sections of AISI 304 sheet form a database for the probabilistic determination of failure-relevant inclusion distribution in fatigue specimens and their corresponding fatigue lifes. By applying the method of Murakami et al. the biggest measured inclusions were used in order to predict the size of failure-relevant inclusions in the fatigue specimens. The location of the crack initiating inclusions was defined based on the modeled inclusion population and the stress distribution in the fatigue specimen, using the probabilistic Monte Carlo framework. Reasonable agreement was obtained between modeling and experimental results.

  19. Active fault creep variations at Chihshang, Taiwan, revealed by creep meter monitoring, 1998-2001

    Science.gov (United States)

    Lee, Jian-Cheng; Angelier, Jacques; Chu, Hao-Tsu; Hu, Jyr-Ching; Jeng, Fu-Shu; Rau, Ruey-Juin

    2003-11-01

    The daily creep meter data recorded at Chihshang in 1998-2001 are presented. The Chihshang creep meter experiment was set up across the Chihshang thrust fault, the most active segment of the Longitudinal Valley Fault, which is the present-day plate suture between the Eurasian and the Philippine Sea plates in eastern Taiwan. Near-continuous data recording at two sites revealed different surface fault motions yet similar annual shortening rates: 16.2 mm at the Tapo site (comprising two connected creep meters) and 15.0 mm at the Chinyuan site (three creep meters straddling parallel fault branches). Four of the five creep meters showed a seasonal variation, with the fault moving steadily during the rainy season from April to October, and remaining quiescent during the rest of the year. The only exception was recorded by the creep meter located on a mélange-composed hillslope, where local gravitational landsliding played an additional role other than tectonic faulting. Through comparison with daily precipitation data, we inferred that moderate rainfall suffices to trigger or facilitate slippage on the surface fault, during the transition period of the dry/wet season. During the observation period from 1998 to 2001, the subsurface seismicity exhibited clusters of microearthquakes on the Chihshang Fault at depths of 10-25 km. Recurrent earthquakes occurred regardless of whether the season was wet or dry, indicating that the stress relaxation associated with seismicity in the seismogenic zone did not transfer immediately up to the surface. The accumulated strain on the Chihshang Fault at shallow surface levels was released through creep during the wet season. In addition to these short-term seasonal variations, an apparent decrease in the annual slipping rate on the Chihshang Fault during the last few years deserves further investigation in order to mitigate against seismic hazard.

  20. Creep Damage Analysis of a Lattice Truss Panel Structure

    Science.gov (United States)

    Jiang, Wenchun; Li, Shaohua; Luo, Yun; Xu, Shugen

    2017-01-01

    The creep failure for a lattice truss sandwich panel structure has been predicted by finite element method (FEM). The creep damage is calculated by three kinds of stresses: as-brazed residual stress, operating thermal stress and mechanical load. The creep damage at tensile and compressive loads have been calculated and compared. The creep rate calculated by FEM, Gibson-Ashby and Hodge-Dunand models have been compared. The results show that the creep failure is located at the fillet at both tensile and creep loads. The damage rate at the fillet at tensile load is 50 times as much as that at compressive load. The lattice truss panel structure has a better creep resistance to compressive load than tensile load, because the creep and stress triaxiality at the fillet has been decreased at compressive load. The maximum creep strain at the fillet and the equivalent creep strain of the panel structure increase with the increase of applied load. Compared with Gibson-Ashby model and Hodge-Dunand models, the modified Gibson-Ashby model has a good prediction result compared with FEM. However, a more accurate model considering the size effect of the structure still needs to be developed.

  1. Creep testing of nodular iron at ambient and elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Martinsson, Aasa; Andersson-Oestling, Henrik C.M.; Seitisleam, Facredin; Wu, Rui; Sandstroem, Rolf (Swerea KIMAB AB, Stockholm (Sweden))

    2010-12-15

    The creep strain at room temperature, 100 and 125 deg C has been investigated for the ferritic nodular cast iron insert intended for use as the load-bearing part of canisters for long term disposal of spent nuclear fuel. The microstructure consisted of ferrite, graphite nodules of different sizes, compacted graphite and pearlite. Creep tests have been performed for up to 41,000 h. The specimens were cut out from material taken from two genuine inserts, I30 and I55. After creep testing, the specimens from the 100 deg C tests were hardness tested and a metallographic examination was performed. Creep strains at all temperatures appear to be logarithmic, and accumulation of creep strain diminishes with time. The time dependence of the creep strain is consistent to the W-model for primary creep. During the loading plastic strains up to 1% appeared. The maximum recorded creep strain after the loading phase was 0.025%. This makes the creep strains technically insignificant. Acoustic emission recordings during the loading of the room temperature tests showed no sounds or other evidence of microcracking during the loading phase. There is no evidence that the hardness or the graphite microstructure changed during the creep tests

  2. Influence of phosphorus on the creep ductility of copper

    Energy Technology Data Exchange (ETDEWEB)

    Sandström, Rolf, E-mail: rsand@kth.se [Materials Science and Engineering, KTH, Brinellvägen 23, S-100 44 Stockholm (Sweden); Swerea KIMAB, Box 7074, S-164 07 Kista (Sweden); Wu, Rui [Swerea KIMAB, Box 7074, S-164 07 Kista (Sweden)

    2013-10-15

    Around 1990 it was discovered that pure copper could have extra low creep ductility in the temperature interval 180–250 °C. The material was intended for use in canisters for nuclear waste disposal. Although extra low creep ductility was not observed much below 180 °C and the temperature in the canister will never exceed 100 °C, it was feared that the creep ductility could reach low values at lower temperatures after long term exposure. If 50 ppm phosphorus was added to the copper the low creep ductility disappeared. A creep cavitation model is presented that can quantitatively describe the cavitation behaviour in uniaxial and multiaxial creep tests as well as the observed creep ductility for copper with and without phosphorus. A so-called double ledge model has been introduced that demonstrates why the nucleation rate of creep cavities is often proportional to the creep rate. The phosphorus agglomerates at the grain boundaries and limits their local deformation and thereby reduces the formation and growth of cavities. This explains why extra low creep ductility does not occur in phosphorus alloyed copper.

  3. Modelling anelastic contribution to nuclear fuel cladding creep and stress relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Tulkki, Ville, E-mail: ville.tulkki@vtt.fi; Ikonen, Timo

    2015-10-15

    In fuel behaviour modelling accurate description of the cladding mechanical response is important for both operational and safety considerations. While accuracy is desired, a certain level of simplicity is needed as both computational resources and detailed information on properties of particular cladding may be limited. Most models currently used in the integral codes divide the mechanical response into elastic and viscoplastic contributions. These have difficulties in describing both creep and stress relaxation, and often separate models for the two phenomena are used. In this paper we implement anelastic contribution to the cladding mechanical model, thus enabling consistent modelling of both creep and stress relaxation. We show that the model based on assumption of viscoelastic behaviour can be used to explain several experimental observations in transient situations and compare the model to published set of creep and stress relaxation experiments performed on similar samples. Based on the analysis presented we argue that the inclusion of anelastic contribution to the cladding mechanical models provides a way to improve the simulation of cladding behaviour during operational transients.

  4. Numerical 2D and 3D Investigation of Non-Metallic (Glass, Carbon) Fiber Pull-Out Micromechanics 9in Concrete Matrix)

    OpenAIRE

    Khabaz, A; Krasņikovs, A; Kononova, O; Mačanovskis, A

    2010-01-01

    Short non-metallic (glass, carbon) fibre use for concrete disperse reinforcment is of particular interest, because of much higher fibre/matrix interface area value comparing to industrially produced steel fibres.

  5. Creep fatigue damage under multiaxial conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lobitz, D.W.; Nickell, R.E.

    1977-01-01

    When structural components are subjected to severe cyclic loading conditions with intermittent periods of sustained loading at elevated temperature, the designer must guard against a failure mode caused by the interaction of time-dependent and time-independent deformation. This phenomena is referred to as creep-fatigue interaction. The most elementary form of interaction theory (called linear damage summation) is now embodied in the ASME Boiler and Pressure Vessel Code. In recent years, a competitor for the linear damage summation theory has emerged, called strainrange partitioning. This procedure is based upon the visualization of the cyclic strain in a uniaxial creep-fatigue test as a hysteresis loop, with the inelastic strains in the loop counter-balanced in one of two ways. The two theories are compared and contrasted in terms of ease of use, possible inconsistencies, and component life prediction. Future work to further test the damage theories is recommended. (TFD)

  6. Cake creep during filtration of flocculated manure

    DEFF Research Database (Denmark)

    Christensen, Morten Lykkegaard; Keiding, Kristian

    the distribution of N and P on the fields. Filtration is a useful method for such a separation. Furthermore, chemicals can be added to flocculate the solids and thereby increase the filterability i.e. the specific filter-cake resistance can be reduced from 1015 m/kg to 1011 m/kg. Both the amount of added chemicals......, and the mixing procedure affect the result, and lab-scale experiments are often used to study how these pre-treatments influence the filtration process. However, the existing mathematical filtration models are based on filtration of inorganic particles and cannot simulate the filtration data obtained when manure...... that the discrepancy between the filtration theory and the observed filtration behaviour is due to a time-dependent collapse of the formed cake (creep). This can also explain the observed behaviour when flocculated manure is filtered. The filtration data can be simulated if cake creep is adopted in the filtration...

  7. Transient effects in friction fractal asperity creep

    CERN Document Server

    Goedecke, Andreas

    2013-01-01

    Transient friction effects determine the behavior of a wide class of mechatronic systems. Classic examples are squealing brakes, stiction in robotic arms, or stick-slip in linear drives. To properly design and understand mechatronic systems of this type, good quantitative models of transient friction effects are of primary interest. The theory developed in this book approaches this problem bottom-up, by deriving the behavior of macroscopic friction surfaces from the microscopic surface physics. The model is based on two assumptions: First, rough surfaces are inherently fractal, exhibiting roughness on a wide range of scales. Second, transient friction effects are caused by creep enlargement of the real area of contact between two bodies. This work demonstrates the results of extensive Finite Element analyses of the creep behavior of surface asperities, and proposes a generalized multi-scale area iteration for calculating the time-dependent real contact between two bodies. The toolset is then demonstrated both...

  8. The Creep of Laminated Synthetic Resin Plastics

    Science.gov (United States)

    Perkuhn, H

    1941-01-01

    The long-time loading strength of a number of laminated synthetic resin plastics was ascertained and the effect of molding pressure and resin content determined. The best value was observed with a 30 to 40 percent resin content. The long-time loading strength also increases with increasing molding pressure up to 250 kg/cm(exp 2); a further rise in pressure affords no further substantial improvement. The creep strength is defined as the load which in the hundredth hour of loading produces a rate of elongation of 5 X 10(exp -4) percent per hour. The creep strength values of different materials were determined and tabulated. The effect of humidity during long-term tests is pointed out.

  9. Very slow creep tests on salt samples

    Directory of Open Access Journals (Sweden)

    de Greef V.

    2010-06-01

    Full Text Available Long-term creep tests have been performed on rock-salt and argillite samples under very small uniaxial loadings (σ = 0.02 to 0.1 MPa . To minimize the effects of temperature variations, testing devices were set in a mine where temperature fluctuations are of the order of one-hundredth of a degree Celsius. The mechanical loading was provided by dead weights. The deformations were measured through special displacement sensors with a resolution of ∆ε = 10-8. Strain rates as small as έ = 7 × 10-13s-1 were measured. These tests allow rock-sample creep to be investigated at very small strain rates. The tests also prove that extrapolation of constitutive laws at very small rates is often incorrect.

  10. Failure of bacterial streamers in creeping flows

    Science.gov (United States)

    Biswas, Ishita; Ghosh, Ranajay; Sadrzadeh, Mohtada; Kumar, Aloke

    2016-11-01

    In the recent years, the dynamical response of filamentous bacterial aggregates called bacterial streamer in creeping flows has attracted attention. We report the observation of 'necking-type' instability leading to failure in bacterial (Pseudomonas fluorescens) streamers formed in creeping flows. Quantification of the failure process was made possible through the use of 200 nm red fluorescent polystyrene tracer particles embedded in the bacterial extracellular polymeric substances (EPS). The nonlinear failure behavior shows distinct phases of deformation with mutually different characteristic times, which end with a distinct localized failure of the streamer. We also develop a simplified analytical model to describe the experimental observations of the failure phenomena. The theoretical power law relationship between critical stretch ratio and the fluid velocity scale matches closely experimental observations.

  11. The effect of dissolved magnesium on creep of calcite II: transition from diffusion creep to dislocation creep

    Science.gov (United States)

    Xu, Lili; Renner, Jörg; Herwegh, Marco; Evans, Brian

    2009-03-01

    We extended a previous study on the influence of Mg solute impurity on diffusion creep in calcite to include deformation under a broader range of stress conditions and over a wider range of Mg contents. Synthetic marbles were produced by hot isostatic pressing (HIP) mixtures of calcite and dolomite powders for different intervals (2-30 h) at 850°C and 300 MPa confining pressure. The HIP treatment resulted in high-magnesian calcite aggregates with Mg content ranging from 0.5 to 17 mol%. Both back-scattered electron images and chemical analysis suggested that the dolomite phase was completely dissolved, and that Mg distribution was homogeneous throughout the samples at the scale of about two micrometers. The grain size after HIP varied from 8 to 31 μm, increased with time at temperature, and decreased with increasing Mg content (>3.0 mol%). Grain size and time were consistent with a normal grain growth equation, with exponents from 2.4 to 4.7, for samples containing 0.5-17.0 mol% Mg, respectively. We deformed samples after HIP at the same confining pressure with differential stresses between 20 and 200 MPa using either constant strain rate or stepping intervals of loading at constant stresses in a Paterson gas-medium deformation apparatus. The deformation tests took place at between 700 and 800°C and at strain rates between 10-6 and 10-3 s-1. After deformation to strains of about 25%, a bimodal distribution of large protoblasts and small recrystallized neoblasts coexisted in some samples loaded at higher stresses. The deformation data indicated a transition in mechanism from diffusion creep to dislocation creep. At stresses below 40 MPa, the strength was directly proportional to grain size and decreased with increasing Mg content due to the reductions in grain size. At about 40 MPa, the sensitivity of log strain rate to log stress, ( n), became greater than 1 and eventually exceeded 3 for stresses above 80 MPa. At a given strain rate and temperature, the stress at

  12. Shark skin effect in creeping films

    CERN Document Server

    Scholle, M

    2006-01-01

    If a body in a stream is provided with small ridges aligned in the local flow direction, a remarkable drag reduction can be reached under turbulent flow conditions. This surprising phenomenon is called the 'shark skin effect'. We demonstrate, that a reduction of resistance can also be reached in creeping flows if the ridges are aligned perpendicular to the flow direction. We especially consider in gravity-driven film flows the effect of the bottom topography on the mean transport velocity.

  13. Zinc alloy enhances strength and creep resistance

    Energy Technology Data Exchange (ETDEWEB)

    Machler, M. [Fisher Gauge Ltd., Peterborough, Ontario (Canada). Fishercast Div.

    1996-10-01

    A family of high-performance ternary zinc-copper-aluminum alloys has been developed that provides higher strength, hardness, and creep resistance than the traditional zinc-aluminum alloys Zamak 3, Zamak 5, and ZA-8. Designated ACuZinc, mechanical properties comparable to those of more expensive materials make it suitable for high-load applications and those at elevated temperatures. This article describes the alloy`s composition, properties, and historical development.

  14. Creep Deformation by Dislocation Movement in Waspaloy

    Directory of Open Access Journals (Sweden)

    Mark Whittaker

    2017-01-01

    Full Text Available Creep tests of the polycrystalline nickel alloy Waspaloy have been conducted at Swansea University, for varying stress conditions at 700 °C. Investigation through use of Transmission Electron Microscopy at Cambridge University has examined the dislocation networks formed under these conditions, with particular attention paid to comparing tests performed above and below the yield stress. This paper highlights how the dislocation structures vary throughout creep and proposes a dislocation mechanism theory for creep in Waspaloy. Activation energies are calculated through approaches developed in the use of the recently formulated Wilshire Equations, and are found to differ above and below the yield stress. Low activation energies are found to be related to dislocation interaction with γ′ precipitates below the yield stress. However, significantly increased dislocation densities at stresses above yield cause an increase in the activation energy values as forest hardening becomes the primary mechanism controlling dislocation movement. It is proposed that the activation energy change is related to the stress increment provided by work hardening, as can be observed from Ti, Ni and steel results.

  15. Steady-State Creep of Asphalt Concrete

    Directory of Open Access Journals (Sweden)

    Alibai Iskakbayev

    2017-02-01

    Full Text Available This paper reports the experimental investigation of the steady-state creep process for fine-grained asphalt concrete at a temperature of 20 ± 2 °С and under stress from 0.055 to 0.311 MPa under direct tension and was found to occur at a constant rate. The experimental results also determined the start, the end point, and the duration of the steady-state creep process. The dependence of these factors, in addition to the steady-state creep rate and viscosity of the asphalt concrete on stress is satisfactorily described by a power function. Furthermore, it showed that stress has a great impact on the specific characteristics of asphalt concrete: stress variation by one order causes their variation by 3–4.5 orders. The described relations are formulated for the steady-state of asphalt concrete in a complex stressed condition. The dependence is determined between stress intensity and strain rate intensity.

  16. Experimental studies of fiber concrete creep

    Directory of Open Access Journals (Sweden)

    Korneeva Irina

    2017-01-01

    Full Text Available The results of two-stage experimental studies of the strength and deformation characteristics of fibrous concrete reinforced with steel fiber. In the experiments we used steel fiber with bent ends, which practically does not form "hedgehogs", which allows to achieve an even distribution of the fiber by volume. At the first stage, the cube and prismatic strength, deformability at central compression, a number of special characteristics are determined: water absorption, frost resistance, abrasion; the optimal percentage of fiber reinforcement and the maximum size of the coarse aggregate fraction were selected. Fiber reinforcement led to an increase in the strength of concrete at compression by 1,35 times and an increase in the tensile strength at bending by 3,4 times. At the second stage, the creep of fibrous concrete and plain concrete of similar composition at different stress levels was researched. Creep curves are plotted. It is shown that the use of fiber reinforcement leads to a decrease in creep strain by 21 to 30 percent, depending on the stress level.

  17. Magnetic field annealing for improved creep resistance

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Michael P.; Ludtka, Gail M.; Ludtka, Gerard M.; Muralidharan, Govindarajan; Nicholson, Don M.; Rios, Orlando; Yamamoto, Yukinori

    2015-12-22

    The method provides heat-resistant chromia- or alumina-forming Fe-, Fe(Ni), Ni(Fe), or Ni-based alloys having improved creep resistance. A precursor is provided containing preselected constituents of a chromia- or alumina-forming Fe-, Fe(Ni), Ni(Fe), or Ni-based alloy, at least one of the constituents for forming a nanoscale precipitate MaXb where M is Cr, Nb, Ti, V, Zr, or Hf, individually and in combination, and X is C, N, O, B, individually and in combination, a=1 to 23 and b=1 to 6. The precursor is annealed at a temperature of 1000-1500.degree. C. for 1-48 h in the presence of a magnetic field of at least 5 Tesla to enhance supersaturation of the M.sub.aX.sub.b constituents in the annealed precursor. This forms nanoscale M.sub.aX.sub.b precipitates for improved creep resistance when the alloy is used at service temperatures of 500-1000.degree. C. Alloys having improved creep resistance are also disclosed.

  18. Creep Damage Characteristics of Soft Rock under Disturbance Loads

    Institute of Scientific and Technical Information of China (English)

    Fu Zhiliang; Guo Hua; Gao Yanfa

    2008-01-01

    This article focuses on the process of rock creep damage and micro-damage evolution properties of gray green mudstone under impacting disturbance load conditions for the first time using the real time computerized tomography (CT) testing technique. The results indicate that axial load comes into limit strength neighborhood, rock micro-crack links into larger crack, creep rate increases in a short time, larger plastic deformation happens; this is called disturbance accelerating creep stage. When rock is within limit strength neighborhood, there occurs creep micro-damage under smaller disturbance load. When disturbance load is larger, rock directly enters into disturbance accelerating creep stage, failure occurs instantaneously. On the basis of experimental research, the CT scanning method was used to describe the creep micro-damage of soft rock, also helpful in the prediction of roadways' service life and evaluation of geotechnicai engineering stability.

  19. Creep Test of Polymer-matrix 3-D Braided Composites

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The long-term creep behavior of polymer-matrix 3-D braided composites was studied by using the tensile creep test method, and the effect of braiding structure, braiding angle and fiber volume fraction were discussed. The creep curve appears as expected, and can be defimed two phases,namely, the primary phase and the secondary phase. For each sample, strain increases with time rapidly, and then the strain rate decreases and appears to approach a constant rate of change (steady-state creep). The experiment results show that the creep resistant properties are improved while the braiding angle decreases or the fiber volume fraction increases, and that the five-directional braiding structure offers better creep resistant properties than the fourdirectional braiding structure.

  20. The role of creep in high temperature low cycle fatigue.

    Science.gov (United States)

    Manson, S. S.; Halford, G. R.; Spera, D. A.

    1971-01-01

    The significance of the role that creep can play in governing high-temperature, low-cycle fatigue resistance is investigated by conducting strain cycling tests on two high-temperature stainless steel alloys and making concurrent measurements of stress, temperature, and strain at various frequencies. The results are then analyzed in terms of damage imposed by creep and fatigue components. It is shown that creep can play an important and sometimes dominant role in low cycle fatigue at high temperatures. The results of the study include the findings that: (1) the simple life-fraction theory described is adequate for calculating creep damage when the cyclic creep rupture curve is used as a basis for analysis; (2) a method of universal slopes originally developed for room temperature use is sufficiently accurate at high temperature to be used to calculate pure fatigue damage; and (3) a linear creep-fatigue damage rule can explain the transitions observed from one failure mode to another.

  1. Inclusions in DKDP crystal

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The shape and the size of inclusions in DKDP crystal have been observed and measured microscopically.Three kinds of inclusions were found and the components of the inclusions were measured. The formation mechanisms were proposed and discussed.``

  2. Degradation of mechanical properties of CrMo creep resistant steel operating under conditions of creep

    Directory of Open Access Journals (Sweden)

    J. Michel

    2012-01-01

    Full Text Available Mechanical properties of a steam tube made of CrMo creep resistant steel are analysed in this contribution after up to 2,6•105 hours service life in creep conditions at temperature 530 °C and calculated stress level in the tube wall 46,5 MPa. During service life there were in the steel gradual micro structure changes, fi rst pearlite spheroidization, precipitation, coaugulation and precipitate coarsening. Nevertheless the strength and deformation properties of the steel (Re, Rm, A5, Z, and the resistance to brittle fracture and the creep strength limit, were near to unchanged after 2,1•105 hours in service. The steam tube is now in service more than 2,6•105 h.

  3. MICROSTRUCTURE AND MECHANICAL PROPERTIES DEGRADATION OF CrMo CREEP RESISTANT STEEL OPERATING UNDER CREEP CONDITIONS

    Directory of Open Access Journals (Sweden)

    Ján Micheľ

    2011-07-01

    Full Text Available In this contribution microstructure degradation of a steam tube is analysed. The tube is made of CrMo creep resistant steel and was in service under creep conditions at temperature 530°C and calculated stress level in the tube wall 46.5 MPa. During service life in the steel gradual micro structure changes were observed, first pearlite spheroidization, precipitation, coagulation and precipitate coarsening. Despite the fact that there were evident changes in the micro structure the strength and deformation properties of the steel (Re, Rm, A5, Z, the resistance to brittle fracture and the creep strength limit, were near to unchanged after 2.1x10 5 hours in service. The steam tube is now in service more than 2.6x10 5 h.

  4. 非金属矿物在医药行业的应用与前景%Medicinal Application and Prospect of Non-metallic Mineral

    Institute of Scientific and Technical Information of China (English)

    鲍康德; 周春晖

    2012-01-01

    Deep procession of non-metallic mineral and application on bio-/medicinal area is a new high-technical industry. This paper summarizes the appl ication history and status in quo of non-metallic minerals in pharmaceutical industry; identification, classification and development tendency of non-metallic minerals for pharmaceutical use. The focus is to introduce the development history of non-metallic minerals for pharmaceutical use, and explore the application prospect of non-metallic minerals in pharmaceutical industry, so as to provide theory basis for sufficiently exploring the potential of non-metallic minerals.%非金属矿物深加工并被用于生物医药领域系高新技术产业.本文综述了非金属矿物的医药应用历史、现状;药用非金属矿物的鉴别、分类和发展趋势.重点介绍了非金属矿物的药用开发历程,并展望了非金属矿物在医药行业的应用前景,以期为充分发掘非金属矿物的潜能提供理论指导.

  5. An aviation security (AVSEC) screening demonstrator for the detection of non-metallic threats at 28-33 GHz

    Science.gov (United States)

    Salmon, Neil A.; Bowring, Nick; Hutchinson, Simon; Southgate, Matthew; O'Reilly, Dean

    2013-10-01

    The unique selling proposition of millimetre wave technology for security screening is that it provides a stand-off or portal scenario sensing capability for non-metallic threats. The capabilities to detect some non-metallic threats are investigated in this paper, whilst recommissioning the AVSEC portal screening system at the Manchester Metropolitan University. The AVSEC system is a large aperture (1.6 m) portal screening imager which uses spatially incoherent illumination at 28-33 GHz from mode scrambling cavities to illuminate the subject. The imaging capability is critically analysed in terms of this illumination. A novel technique for the measurement of reflectance, refractive index and extinction coefficient is investigated and this then use to characterise the signatures of nitromethane, hexane, methanol, bees wax and baking flour. Millimetre wave images are shown how these liquids in polycarbonate bottles and the other materials appear against the human body.

  6. Study of creep cavitation in a stainless steel weldment

    OpenAIRE

    Jazaeri, H.; Bouchard, P. J.; Hutchings, M; Lindner, P.

    2012-01-01

    A study of creep cavities near reheat cracking in AISI Type 316H austenitic stainless steel headers, removed from long-time high temperature operation in nuclear power plants, is reported. It is shown how application of scanning electron microscopy (SEM), cryogenic fractography and small angle neutron scattering (SANS) can be applied, in a complementary way, to observe and quantify creep cavitation damage. Creep cavities in the vicinity of the crack are found to be mainly surrounding inter-gr...

  7. Viscous Creep in Dry Unconsolidated Gulf of Mexico Shale

    Science.gov (United States)

    Chang, C.; Zoback, M. D.

    2002-12-01

    We conducted laboratory experiments to investigate creep characteristics of dry unconsolidated shale recovered from the pathfinder well, Gulf of Mexico (GOM). We subjected jacketed cylindrical specimens (25.4 mm diameter) to hydrostatic pressure that increased from 10 to 50 MPa in steps of 5 MPa. We kept the pressure constant in each step for at least 6 hours and measured axial and lateral strains (provided by LVDTs) and ultrasonic velocities (provided by seismic-wave transducers). The dry shale exhibited pronounced creep strain at all pressure levels, indicating that the dry frame of the shale possesses an intrinsic viscous property. Interestingly, the creep behavior of the shale is different above and below 30 MPa confining pressure. Above 30 MPa, the amount of creep strain in 6 hours is nearly constant with equal pressurization steps, indicating a linear viscous rheology. Below 30 MPa, the amount of creep increases linearly as pressure is raised in constant incremental steps, suggesting that the creep deformation accelerates as pressure increases within this pressure range. Thus, the general creep behavior of the GOM shale is characterized by a bilinear dependence on pressure magnitude. This creep characteristic is quite different from that observed in unconsolidated reservoir sands (Hagin and Zoback, 2002), which exhibited nearly constant amount of creep regardless of the pressure magnitude for equal increasing steps of pressure. The shale exhibits a lack of creep (and nearly negligible strain recovery) when unloaded, suggesting that the creep strain is irrecoverable and can be considered viscoplastic deformation. SEM observations show that the major mechanism of compaction of the dry shale appears to be packing of clay and a progressive collapse of pore (void) spaces. Creep compaction is considerably more significant than compaction that occurs instantaneously, indicating that the process of shale compaction is largely time-dependent.

  8. Stability of MC Carbide Particles Size in Creep Resisting Steels

    Directory of Open Access Journals (Sweden)

    Vodopivec, F.

    2006-01-01

    Full Text Available Theoretical analysis of the dependence microstructure creep rate. Discussion on the effects of carbide particles size and their distribution on the base of accelerated creep tests on a steel X20CrMoV121 tempered at 800 °C. Analysis of the stability of carbide particles size in terms of free energy of formation of the compound. Explanation of the different effect of VC and NbC particles on accelerated creep rate.

  9. Control of Early Age Concrete. Phase 3: Creep in Concrete

    DEFF Research Database (Denmark)

    Hauggaard-Nielsen, Anders Boe; Damkilde, Lars; Hansen, Per Freiesleben

    1997-01-01

    The mechanical properties of the "Road Directorate Concrete" at early ages are studied. Creep in tension at 24 and 72 maturity hours are measured on dogbone shaped specimens. The development of tensile modulus of elasticity and strength are measured with a method developed here. The results...... are compared to compression values and splitting strengths. It is found that the properties of creep in tension are similar to the properties in compression. Further the influence form temperature on creep is found to be significant....

  10. Comparison of creep of the cement pastes included fly ash

    Directory of Open Access Journals (Sweden)

    Padevět Pavel

    2017-01-01

    Full Text Available The paper is devoted to comparison of creep of cement pastes containing fly ash admixture. The size of creep in time depends on the amount of components of the cement paste. Attention is paid to the content of classical fly ash in cement paste and its impact on the size of creep. The moisture of cement pastes is distinguished because it significantly affects the rheological properties of the material.

  11. ANALYSIS METHODS ON STABILITY OF TALL AND BEDDIIG CREEP SLOPE

    Institute of Scientific and Technical Information of China (English)

    RUIYongqin; JIANGZhiming; LIUJinghui

    1995-01-01

    Based on the model of slope engineering geology,the creep and its failure mechanism of tall and bedding slope are deeply analyzed in this paper .The creep laws of weak intercalations are also discussed.The analysis om the stability of creep slope and the age forecasting of sliding slope have been conducted through mumerical simulations using Finite Element Method (FEM)and Dintimct Element Method(DEM).

  12. Creep damage and expected creep life for welded 9-11% Cr steels

    Energy Technology Data Exchange (ETDEWEB)

    Auerkari, P. [VTT Technical Research Centre of Finland, P.O. Box 1000, 02044 (Finland)]. E-mail: Pertti.Auerkari@vtt.fi; Holmstroem, S. [VTT Technical Research Centre of Finland, P.O. Box 1000, 02044 (Finland); Veivo, J. [VTT Technical Research Centre of Finland, P.O. Box 1000, 02044 (Finland); Salonen, J. [VTT Technical Research Centre of Finland, P.O. Box 1000, 02044 (Finland)

    2007-01-15

    The damage mechanisms affecting engineering steels at high-temperatures include creep cavitation and cracking that can form the path for final failure in susceptible locations such as welds. The evolution of observed damage is widely used in condition monitoring, timing of inspections and support of life management. However, the damage evolution is material dependent, and requires confirmation from inspection data. For most low-alloy steels, compilations of inspection data have been applied to establish guidelines for this purpose. Useful experience of the in-service damage is less easily available from newer steels, and infrequently reported from e.g. the 9-11% chromium (Cr) steels that are used in hot steam lines of power plants. However, even then the expected damage evolution can be characterised by using high tensile multi-axiality for damage acceleration. This approach is also useful for ductile steels with relatively slow development of creep cavitation in conventional creep testing. The inspection experience shows very modest creep cavitation in the conventional 11% Cr steel X20CrMoV11-1 even after long-term service. This is of particular interest also because early creep failures have been reported from steam systems made of P91 (X10CrMoVNb9-1). The differences between these steels appear to be largely related to the extent precipitation hardening is utilized in providing creep strength. With more efficient precipitation hardening, P91 and other new high chromium steels are more susceptible than X20 to deviations in e.g. heat treatments.

  13. Toward environmentally-benign utilization of nonmetallic fraction of waste printed circuit boards as modifier and precursor

    Energy Technology Data Exchange (ETDEWEB)

    Hadi, Pejman; Ning, Chao; Ouyang, Weiyi; Xu, Meng [Chemical and Biomolecular Engineering Department, Hong Kong University of Science and Technology, Clear Water Bay Road, Hong Kong Special Administrative Region (Hong Kong); Lin, Carol S.K. [School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong Special Administrative Region (Hong Kong); McKay, Gordon, E-mail: kemckayg@ust.hk [Chemical and Biomolecular Engineering Department, Hong Kong University of Science and Technology, Clear Water Bay Road, Hong Kong Special Administrative Region (Hong Kong); Division of Sustainable Development, College of Science, Engineering and Technology, Hamad bin Khalifa University, Doha (Qatar)

    2015-01-15

    Highlights: • Environmental impacts of electronic waste and specifically waste printed circuit boards. • Review of the recycling techniques of waste printed circuit boards. • Advantages of physico-mechanical recycling techniques over chemical methods. • Utilization of nonmetallic fraction of waste printed circuit boards as modifier/filler. • Recent advances in the use of nonmetallic fraction of waste printed circuit boards as precursor. - Abstract: Electronic waste, including printed circuit boards, is growing at an alarming rate due to the accelerated technological progress and the shorter lifespan of the electronic equipment. In the past decades, due to the lack of proper economic and environmentally-benign recycling technologies, a major fraction of e-waste generated was either destined to landfills or incinerated with the sole intention of its disposal disregarding the toxic nature of this waste. Recently, with the increasing public awareness over their environment and health issues and with the enaction of more stringent regulations, environmentally-benign recycling has been driven to be an alternative option partially replacing the traditional eco-unfriendly disposal methods. One of the most favorable green technologies has been the mechanical separation of the metallic and nonmetallic fraction of the waste printed circuit boards. Although metallic fraction, as the most profitable component, is used to generate the revenue of the separation process, the nonmetallic fraction (NMF) has been left isolated. Herein, the recent developments in the application of NMF have been comprehensively reviewed and an eco-friendly emerging usage of NMF as a value-added material for sustainable remediation has been introduced.

  14. A computer controlled mass spectrometer system for investigating the decomposition of non-metallic materials under atmospheric conditions

    Science.gov (United States)

    Thompson, J. M.

    1985-01-01

    A PDP 11/23 quadrupole mass spectrometer system was coupled to a nondiscriminating gas inlet system permitting gases at atmospheric pressure to be admitted into a high vacuum chamber containing the ion source of the mass spectrometer without separation of the gaseous components. The resolution of related software problems has resulted in a convenient computer-mass spectrometer system capable of generating masses, relative intensities and related data on the gaseous products resulting from the atmospheric thermal decomposition of nonmetallic materials.

  15. A computer controlled mass spectrometer system for investigating the decomposition of non-metallic materials under atmospheric conditions

    Science.gov (United States)

    Thompson, J. M.

    1985-01-01

    A PDP 11/23 quadrupole mass spectrometer system was coupled to a nondiscriminating gas inlet system permitting gases at atmospheric pressure to be admitted into a high vacuum chamber containing the ion source of the mass spectrometer without separation of the gaseous components. The resolution of related software problems has resulted in a convenient computer-mass spectrometer system capable of generating masses, relative intensities and related data on the gaseous products resulting from the atmospheric thermal decomposition of nonmetallic materials.

  16. Creep strength and ductility of 9 to 12% chromium steels

    DEFF Research Database (Denmark)

    Hald, John

    2004-01-01

    Steels", which covers creep data development and analysis for parent materials and welds of all ferritic creep resistant steels ranging from low alloy steels up to 12%Cr steels. The opinions stated in the paper represent the views of the author rather than the whole ECCC WG3A group.......The present paper focuses in on long-term creep properties of parent material of the new 9-12%Cr creep resistant steels, P91, E911 and P92 developed for use in advanced ultrasupercritical power plants. These steels have been at the center of activities in the ECCC Working Group 3A (WG3A) "Ferritic...

  17. A Study of the Creep Effect in Loudspeaker Suspension

    DEFF Research Database (Denmark)

    Agerkvist, Finn T.; Thorborg, Knud; Tinggaard, Carsten

    2008-01-01

    This paper investigates the creep effect, the visco elastic behaviour of loudspeaker suspension parts, which can be observed as an increase in displacement far below the resonance frequency. The creep effect means that the suspension cannot be modelled as a simple spring. The need for an accurate...... creep model is even larger as the validity of loudspeaker models are now sought extended far into the nonlinear domain of the loudspeaker. Different creep models are investigated and implemented both in simple lumped parameter models as well as time domain non-linear models, the simulation results...

  18. Shear creep characteristics and constitutive model of limestone

    Institute of Scientific and Technical Information of China (English)

    Yu Mei; Mao Xianbiao; Hu Xinyu

    2016-01-01

    The characters of limestone in weak interlayer of a high rocky slope in Xuzhou, China, are studied by shear static test and shear creep test. The results show that limestone specimens have attenuation creep properties and constant rate creep properties, almost have no accelerated creep properties. The exponen-tial type empirical formula is selected to fit creep grading curves by polynomial regression analysis method, and the square sums of the fitting results residual are in the order of 10-7. Then grade creep curves at every shear loads are set up. Combining creep rate-time curve, the creep properties of limestone are analyzed. As the physical meaning of component model is clearer, the Poytin–Thomson model is set up. Through the least square method, the optimal parameters of Poytin–Thomson model are obtained, and the sums of squared residuals belong to 10-3 order of magnitude, which can meet the accuracy requirements of engineering calculation. So the Poytin–Thomson model can reflect the shear creep char-acteristics of limestone very well.

  19. Contribution to irradiation creep arising from gas-driven bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Woo, C.H. [Hong Kong Polytechnic Univ., Kowloon (Hong Kong); Garner, F.A. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    In a previous paper the relationship was defined between void swelling and irradiation creep arising from the interaction of the SIPA and SIG creep-driven deformation and swelling-driven deformation was highly interactive in nature, and that the two contributions could not be independently calculated and then considered as directly additive. This model could be used to explain the recent experimental observation that the creep-swelling coupling coefficient was not a constant as previously assumed, but declined continuously as the swelling rate increased. Such a model thereby explained the creep-disappearance and creep-damping anomalies observed in conditions where significant void swelling occurred before substantial creep deformation developed. At lower irradiation temperatures and high helium/hydrogen generation rates, such as found in light water cooled reactors and some fusion concepts, gas-filled cavities that have not yet exceeded the critical radius for bubble-void conversion should also exert an influence on irradiation creep. In this paper the original concept is adapted to include such conditions, and its predictions then compared with available data. It is shown that a measurable increase in the creep rate is expected compared to the rate found in low gas-generating environments. The creep rate is directly related to the gas generation rate and thereby to the neutron flux and spectrum.

  20. Creep strength and ductility of 9 to 12% chromium steels

    DEFF Research Database (Denmark)

    Hald, John

    2004-01-01

    The present paper focuses in on long-term creep properties of parent material of the new 9-12%Cr creep resistant steels, P91, E911 and P92 developed for use in advanced ultrasupercritical power plants. These steels have been at the center of activities in the ECCC Working Group 3A (WG3A) "Ferritic...... Steels", which covers creep data development and analysis for parent materials and welds of all ferritic creep resistant steels ranging from low alloy steels up to 12%Cr steels. The opinions stated in the paper represent the views of the author rather than the whole ECCC WG3A group....

  1. Probabilistic models for creep-fatigue in a steel alloy

    Science.gov (United States)

    Ibisoglu, Fatmagul

    In high temperature components subjected to long term cyclic operation, simultaneous creep and fatigue damage occur. A new methodology for creep-fatigue life assessment has been adopted without the need to separate creep and fatigue damage or expended life. Probabilistic models, described by hold times in tension and total strain range at temperature, have been derived based on the creep rupture behavior of a steel alloy. These models have been validated with the observed creep-fatigue life of the material with a scatter band close to a factor of 2. Uncertainties of the creep-fatigue model parameters have been estimated with WinBUGS which is an open source Bayesian analysis software tool that uses Markov Chain Monte Carlo method to fit statistical models. Secondly, creep deformation in stress relaxation data has been analyzed. Well performing creep equations have been validated with the observed data. The creep model with the highest goodness of fit among the validated models has been used to estimate probability of exceedance at 0.6% strain level for the steel alloy.

  2. Characterization of impact damage in metallic/nonmetallic composites using x-ray computed tomography imaging

    Science.gov (United States)

    Green, William H.; Wells, Joseph M.

    1999-12-01

    Characterizing internal impact damage in composites can be difficult, especially in structurally complex composites or those consisting of many materials. Many methods for nondestructive inspection/nondestructive testing (NDI/NDT) of materials have been known and in use for many years, including x-ray film, real-time, and digital radiographic techniques, and ultrasonic techniques. However, these techniques are generally not capable of three-dimensional (3D) mapping of complex damage patterns, which is necessary to visualize and understand damage cracking modes. Conventional x-ray radiography suffers from the loss of 3D information. Structural complexity and signal dispersion in materials with many interfaces significantly effect ultrasonic inspection techniques. This makes inspection scan interpretation difficult, especially in composites containing a number of different materials (i.e., polymer, ceramic, and metallic). X-ray computed tomography (CT) is broadly applicable to any material or test object through which a beam of penetrating radiation may be passed and detected, including metals, plastics, ceramics, metallic/nonmetallic composites, and assemblies. The principal advantage of CT is that it provides densitometric (that is, radiological density and geometry) images of thin cross sections through an object. Because of the absence of structural superposition, images are much easier to interpret than conventional radiological images. The user can quickly learn to read CT data because images correspond more closely to the way the human mind visualizes 3D structures than projection radiology (that is, film radiography, real-time radiography (RTR), and digital radiography (DR)). Any number of CT images, or slices, from scanning an object can be volumetrically reconstructed to produce a 3D attenuation map of the object. The 3D attenuation data can be rendered using multiplanar or 3D solid visualization. In multiplanar visualization there are four planes of view

  3. Formation of a deposit on workpiece surface in polishing nonmetallic materials

    Science.gov (United States)

    Filatov, Yu. D.; Monteil, G.; Sidorko, V. I.; Filatov, O. Y.

    2013-05-01

    During the last decades in the theory of machining nonmetallic materials some serious advances have been achieved in the field of applying fundamental scientific approaches to the grinding and polishing technologies for high-quality precision surfaces of electronic components, optical systems, and decorative articles made of natural and synthetic stone [1-9]. These achievements include a cluster model of material removal in polishing dielectric workpieces [1-3, 6-7] and a physical-statistical model of formation of debris (wear) particles and removal thereof from a workpiece surface [8-10]. The aforesaid models made it possible to calculate, without recourse to Preston's linear law, the removal rate in polishing nonmetallic materials and the wear intensity for bound-abrasive tools. Equally important for the investigation of the workpiece surface generation mechanism and formation of debris particles are the kinetic functions of surface roughness and reflectance of glass and quartz workpiece surfaces, which have been established directly in the course of polishing. During the in situ inspection of a workpiece surface by laser ellipsometry [11] and reflectometry [12] it was found out that the periodic change of the light reflection coefficient of a workpiece surface being polished is attributed to the formation of fragments of a deposit consisting of work material particles (debris particles) and tool wear particles [13, 14]. The subsequent studies of the mechanism of interaction between the debris particles and wear particles in the tool-workpiece contact zone, which were carried out based on classical concepts [15, 16], yielded some unexpected results. It was demonstrated that electrically charged debris and wear particles, which are located in the coolant-filled gap between a tool and a workpiece, move by closed circular trajectories enclosed in spheres measuring less than one fifth of the gap thickness. This implies that the probability of the debris and wear

  4. Estimation of transient creep C(t)-integrals for SE(B) specimen under elastic-plastic creep

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Han Sang; Je, Jin Ho; Kim, Dong Jun; Kim, Yun Jae [Dept. of Mechanical Engineering, Korea University, Seoul (Korea, Republic of)

    2015-09-15

    In this paper, we estimate the time-dependent C(t) integrals under elastic-plastic-creep conditions. Finite-element (FE) transient creep analyses have been performed for single-edge-notched-bend (SEB) specimens. We investigate the effect of the initial plasticity on the transient creep by systematically varying the magnitude of the initial step load. We consider both the same stress exponent and different stress exponents in the power-law creep and plasticity to elastic-plastic-creep behavior. To estimate the C(t) integrals, we compare the FE analysis results with those obtained using formulas. In this paper, we propose a modified equation to predict the C(t) integrals for the case of creep exponents that are different from the plastic exponent.

  5. Estimation of transient creep crack-tip stress fields for SE(B) specimen under elastic-plastic-creep conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Han Sang; Je, Jin Ho; Kim, Dong Jun; Kim, Yun Jae [Dept. of Mechanical Engineering, Korea University, Seoul (Korea, Republic of)

    2015-10-15

    This paper estimates the time-dependent crack-tip stress fields under elastic-plastic-creep conditions. We perform Finite-Element (FE) transient creep analyses for a Single-Edge-notched-Bend (SEB) specimen. We investigate the effect of the initial plasticity on the transient creep by systematically varying the magnitude of the initial step-load. We consider both the same stress exponent and different stress exponent in the power-law creep and plasticity to determine the elastic-plastic-creep behaviour. To estimation of the crack-tip stress fields, we compare FE analysis results with those obtained numerically formulas. In addition, we propose a new equation to predict the crack-tip stress fields when the creep exponent is different from the plastic exponent.

  6. Recovery of creep properties of the nickel-base superalloy nimonic 105

    CSIR Research Space (South Africa)

    Girdwood, RB

    1996-01-01

    Full Text Available -crept samples and creep recovery quantitatively assessed. Microstructural damage occurring during the creep of Nimonic 105 was studied. Creep strength is lost by the coarsening of the precipitate and grain boundary carbides. The Theta Projection Concept relates...

  7. Determinants of Electricity Demand in Nonmetallic Mineral Products Industry: Evidence from a Comparative Study of Japan and China

    Directory of Open Access Journals (Sweden)

    Gang Du

    2015-06-01

    Full Text Available Electricity intensity is an important indicator for measuring production efficiency. A comparative study could offer a new perspective on investigating determinants of electricity demand. The Japanese non-metallic mineral products industry is chosen as the object for comparison considering its representative position in production efficiency. By adopting the cointegration model, this paper examines influencing factors of electricity demand in Japanese and Chinese non-metallic mineral products industries under the same framework. Results indicate that although economic growth and industrial development stages are different between the two countries, major factors that affect the sectoral energy consumption are the same. Specifically, economic growth and industrial activity contribute to the growth of sectoral electricity consumption, while R&D intensity, per capita productivity and electricity price are contributors to the decline of sectoral electricity consumption. Finally, in order to further investigate the development trend of sectoral electricity demand, future electricity consumption and conservation potential are predicted under different scenarios. Electricity demand of the Chinese non-metallic mineral products industry is predicted to be 680.53 TWh (terawatt-hours in 2020 and the sectoral electricity conservation potentials are estimated to be 118.26 TWh and 216.25 TWh under the moderate and advanced electricity-saving scenarios, respectively.

  8. VALIDATION OF AN ALGORITHM FOR NONMETALLIC INTRAOCULAR FOREIGN BODIES' COMPOSITION IDENTIFICATION BASED ON COMPUTED TOMOGRAPHY AND MAGNETIC RESONANCE IMAGING.

    Science.gov (United States)

    Moisseiev, Elad; Barequet, Dana; Zunz, Eran; Barak, Adiel; Mardor, Yael; Last, David; Goez, David; Segal, Zvi; Loewenstein, Anat

    2015-09-01

    To validate and evaluate the accuracy of an algorithm for the identification of nonmetallic intraocular foreign body composition based on computed tomography and magnetic resonance imaging. An algorithm for the identification of 10 nonmetallic materials based on computed tomography and magnetic resonance imaging has been previously determined in an ex vivo porcine model. Materials were classified into 4 groups (plastic, glass, stone, and wood). The algorithm was tested by 40 ophthalmologists, which completed a questionnaire including 10 sets of computed tomography and magnetic resonance images of eyes with intraocular foreign bodies and were asked to use the algorithm to identify their compositions. Rates of exact material identification and group identification were measured. Exact material identification was achieved in 42.75% of the cases, and correct group identification in 65%. Using the algorithm, 6 of the materials were exactly identified by over 50% of the participants, and 7 were correctly classified according to their groups by over 75% of the materials. The algorithm was validated and was found to enable correct identification of nonmetallic intraocular foreign body composition in the majority of cases. This is the first study to report and validate a clinical tool allowing intraocular foreign body composition based on their appearance in computed tomography and magnetic resonance imaging, which was previously impossible.

  9. Collect Available Creep-Fatigue Data and Study Existing Creep-Fatigue Evaluation Procedures for Grade 91 and Hastelloy XR

    Energy Technology Data Exchange (ETDEWEB)

    Tai Asayama; Yukio Tachibana

    2007-09-30

    This report describes the results of investigation on Task 5 of DOE/ASME Materials Project based on a contract between ASME Standards Technology, LLC (ASME ST-LLC) and Japan Atomic Energy Agency (JAEA). Task 5 is to collect available creep-fatigue data and study existing creep-fatigue evaluation procedures for Grade 91 steel and Hastelloy XR. Part I of this report is devoted to Grade 91 steel. Existing creep-fatigue data were collected (Appendix A) and analyzed from the viewpoints of establishing a creep-fatigue procedure for VHTR design. A fair amount of creep-fatigue data has been obtained and creep-fatigue phenomena have been clarified to develop design standards mainly for fast breeder reactors. Following this, existing creep-fatigue procedures were studied and it was clarified that the creep-fatigue evaluation procedure of the ASME-NH has a lot of conservatisms and they were analyzed in detail from the viewpoints of the evaluation of creep damage of material. Based on the above studies, suggestions to improve the ASME-NH procedure along with necessary research and development items were presented. Part II of this report is devoted to Hastelloy XR. Existing creep-fatigue data used for development of the high temperature structural design guideline for High Temperature Gas-cooled Reactor (HTGR) were collected. Creep-fatigue evaluation procedure in the design guideline and its application to design of the intermediate heat exchanger (IHX) for High Temperature Engineering Test Reactor (HTTR) was described. Finally, some necessary research and development items in relation to creep-fatigue evaluation for Gen IV and VHTR reactors were presented.

  10. Creep and creep-rupture behavior of a continuous strand, swirl mat reinforced polymer composite in automotive environments

    Energy Technology Data Exchange (ETDEWEB)

    Ren, W.; Brinkman, C.R. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1998-12-31

    Creep and creep-rupture behavior of an isocyanurate based polyurethane matrix with a continuous strand, swirl mat E-glass reinforcement was investigated for automotive applications. The material under stress was exposed to various automobile service environments. Results show that environment has substantial effects on its creep and creep-rupture properties. Proposed design guide lines and stress reduction factors were developed for various automotive environments. These composites are considered candidate structural materials for light weight and fuel efficient automobiles of the future.

  11. STUDY ABOUT THE ORIGIN OF INCLUSIONS IN THE TUNDISH OF TERNIUM SIDERAR

    Directory of Open Access Journals (Sweden)

    Alejandro Martín

    2012-12-01

    Full Text Available For the production of steels with high quality standards is essential to know accurately the different sources that generate inclusions, in order to optimize the steelmaking practices and to minimize their frequency. The use of tracer elements in the slag has shown an effective tool to determine the origin of inclusions in continuous casting slabs. In the present study different experiences were performed using BaCO3 like a tracer in the tundish slag. Using this methodology slab samples were taken at different times of the castings. The samples were exhaustively analyzed by optical microscopy and SEM/EDS. The density, size distribution and composition of the inclusions observed were evaluated. The results of this analysis revealed the presence of inclusions with Ba in the slab during the transitory state (ladle change. For another hand, samples from the stationary state did not detect this type of inclusions. Ba inclusions occur most frequently in advanced casting sequence and in those cases where the tundish level has a weight reduction during the ladle change. These results suggest that the emulsification produced by the impact of the flow of liquid steel can generate inclusions. The effect is more pronounced when there is a greater accumulation of slag in the tundish. Finally, various tests are also performed using flow modifiers within the tundish, analyzing their impact on the generation and elimination of non-metallic inclusions

  12. Activity concentration of natural radioactive nuclides in nonmetallic industrial raw materials in Japan.

    Science.gov (United States)

    Iwaoka, Kazuki; Tabe, Hiroyuki; Yonehara, Hidenori

    2014-11-01

    Natural materials such as rock, ore, and clay, containing natural radioactive nuclides are widely used as industrial raw materials in Japan. If these are high concentrations, the workers who handle the material can be unknowingly exposed to radiation at a high level. In this study, about 80 nonmetallic natural materials frequently used as industrial raw materials in Japan were comprehensively collected from several industrial companies, and the activity concentrations of (238)U series, (232)Th series and (40)K in the materials was determined by ICP-MS (inductively-coupled plasma mass spectrometer) and gamma ray spectrum analyses. Effective doses to workers handling them were estimated by using methods for dose estimation given in the RP 122. We found the activity concentrations to be lower than the critical values defined by regulatory requirements as described in the IAEA Safety Guide. The maximum estimated effective dose to workers handling these materials was 0.16 mSv y(-1), which was lower than the reference level (1-20 mSv y(-1)) for existing situation given in the ICRP Publ.103.

  13. Strength and deformability of concrete beams reinforced by non-metallic fiber and composite rebar

    Science.gov (United States)

    Kudyakov, K. L.; Plevkov, V. S.; Nevskii, A. V.

    2015-01-01

    Production of durable and high-strength concrete structures with unique properties has always been crucial. Therefore special attention has been paid to non-metallic composite and fiber reinforcement. This article describes the experimental research of strength and deformability of concrete beams with dispersed and core fiber-based reinforcement. As composite reinforcement fiberglass reinforced plastic rods with diameters 6 mm and 10 mm are used. Carbon and basalt fibers are used as dispersed reinforcement. The developed experimental program includes designing and production of flexural structures with different parameters of dispersed fiber and composite rebar reinforcement. The preliminary testing of mechanical properties of these materials has shown their effectiveness. Structures underwent bending testing on a special bench by applying flexural static load up to complete destruction. During the tests vertical displacements were recorded, as well as value of actual load, slippage of rebars in concrete, crack formation. As a result of research were obtained structural failure and crack formation graphs, value of fracture load and maximum displacements of the beams at midspan. Analysis of experimental data showed the effectiveness of using dispersed reinforcement of concrete and the need for prestressing of fiberglass composite rebar.

  14. Stepped-Frequency Ground-Penetrating Radar for Detection of Small Non-metallic Buried Objects

    DEFF Research Database (Denmark)

    Jakobsen, Kaj Bjarne; Sørensen, Helge Bjarup Dissing; Nymann, Ole

    1997-01-01

    to an HP8753C Network Analyzer through a 5 m long Sucoflex coaxial cable. The data are collected automatically using an HPIB interface. The collected data contains both the amplitude and phase information of the reflection coefficient. Data are measured at up to a maximum of 401 different frequencies...... at each measurement point using a mesh-grid with a resolution down to 1 mm by 1 mm. The size of the scan area is 1410 mm by 210 mm. Measurements have been performed on loamy soil containing a buried M-56, a non-metallic AP-mine, and various other mine-like objects made of solid plastic, brass, aluminum......, steel, and wood. The presented results are based on probe-data measured at 100 different frequencies at each measurement point and a coarser mesh-grid of 10 mm by 10 mm, since it is found that less probe-data is needed. Our experiments show that even less amount of probe-data may be necessary....

  15. Creep of trabecular bone from the human proximal tibia

    Energy Technology Data Exchange (ETDEWEB)

    Novitskaya, Ekaterina, E-mail: eevdokim@ucsd.edu [Mechanical and Aerospace Engineering, UC, San Diego, La Jolla, CA 92093 (United States); Materials Science and Engineering Program, UC, San Diego, La Jolla, CA 92093 (United States); Zin, Carolyn [Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218 (United States); Chang, Neil; Cory, Esther; Chen, Peter [Departments of Bioengineering and Orthopaedic Surgery, UC, San Diego, La Jolla, CA 92093 (United States); D’Lima, Darryl [Shiley Center for Orthopaedic Research and Education, Scripps Health, La Jolla, CA 92037 (United States); Sah, Robert L. [Materials Science and Engineering Program, UC, San Diego, La Jolla, CA 92093 (United States); Departments of Bioengineering and Orthopaedic Surgery, UC, San Diego, La Jolla, CA 92093 (United States); McKittrick, Joanna [Mechanical and Aerospace Engineering, UC, San Diego, La Jolla, CA 92093 (United States); Materials Science and Engineering Program, UC, San Diego, La Jolla, CA 92093 (United States)

    2014-07-01

    Creep is the deformation that occurs under a prolonged, sustained load and can lead to permanent damage in bone. Creep in bone is a complex phenomenon and varies with type of loading and local mechanical properties. Human trabecular bone samples from proximal tibia were harvested from a 71-year old female cadaver with osteoporosis. The samples were initially subjected to one cycle load up to 1% strain to determine the creep load. Samples were then loaded in compression under a constant stress for 2 h and immediately unloaded. All tests were conducted with the specimens soaked in phosphate buffered saline with proteinase inhibitors at 37 °C. Steady state creep rate and final creep strain were estimated from mechanical testing and compared with published data. The steady state creep rate correlated well with values obtained from bovine tibial and human vertebral trabecular bone, and was higher for lower density samples. Tissue architecture was analyzed by micro-computed tomography (μCT) both before and after creep testing to assess creep deformation and damage accumulated. Quantitative morphometric analysis indicated that creep induced changes in trabecular separation and the structural model index. A main mode of deformation was bending of trabeculae. - Highlights: • Compressive creep tests of human trabecular bone across the tibia were performed. • The creep rate was found to be inversely proportional to the density of the samples. • μ-computed tomography before and after testing identified regions of deformation. • Bending of the trabeculae was found to be the main deformation mode.

  16. Creep life simulations of EB welded copper overpack

    Energy Technology Data Exchange (ETDEWEB)

    Holmstroem, S.; Laukkanen, A.; Andersson, T. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2013-12-15

    The long term life predictions of copper overpack (sealed by EB welding in Finland) have previously been based on stress estimations that vary over a wide range, typically between 40-100 MPa. These values are usually not based on structural calculation including the EB-weld that increases the complexity of the stress state in the copper overpack. This report will attempt to pinpoint and simulate the stresses and strains developing in the copper overpack during its first decennia of repository service by advanced FEA simulations including the impact of the EB-weld. The main challenge of this work is the extrapolation of the creep strain response of OFP copper to the service relevant loads and temperatures. The uniaxial creep model is translated to a multiaxial constitutive equation form with adequate computational efficiency. The copper overpack strain and stress evolution has been simulated at up to 100 000 years at a conservative constant temperature of 80 deg C with 14 MPa of external pressure. The results indicate rapid creep relaxation in the initial stages after the load has been applied followed by limited creep strain accumulation thereafter. Local elastic-plastic and creep deformation is predicted at the EB weld root with a total strain of below 12 %. The predicted stresses after external loading and short term relaxation are moderate and the impact of weld residual stresses and the lower creep rupture properties of the EB seem not to be detrimental to the predicted long term creep response. The simulation results imply that the most crucial impact on the creep strain accumulation of the copper overpack is related to the OFP copper primary creep properties. The present study predicts sufficiently low creep strains for a 100 000 years canister life with the conservative assumption at a constant temperature of 80 deg C. However a sensitivity study on the impact of primary creep is strongly recommended due to contradicting analysis results from earlier FEA

  17. Limits to Inclusion

    Science.gov (United States)

    Hansen, Janne Hedegaard

    2012-01-01

    In this article, I will argue that a theoretical identification of the limit to inclusion is needed in the conceptual identification of inclusion. On the one hand, inclusion is formulated as a vision that is, in principle, limitless. On the other hand, there seems to be an agreement that inclusion has a limit in the pedagogical practice. However,…

  18. Limits to Inclusion

    Science.gov (United States)

    Hansen, Janne Hedegaard

    2012-01-01

    In this article, I will argue that a theoretical identification of the limit to inclusion is needed in the conceptual identification of inclusion. On the one hand, inclusion is formulated as a vision that is, in principle, limitless. On the other hand, there seems to be an agreement that inclusion has a limit in the pedagogical practice. However,…

  19. Creep and Creep Crack Growth Behaviors for SMAW Weldments of Gr. 91 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo Gon; Yin, Song Nan; Park, Ji Yeon; Hong, Sung Deok; Kim, Yong Wan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Jae Young [Pukyong National University, Busan (Korea, Republic of)

    2010-05-15

    High Cr ferritic resistance steels with tempered martensite microstructures posses enhanced creep strength at the elevated temperatures. Those steels as represented by a modified 9Cr-1Mo steel (ASME Grade 91, hereafter Gr.91) are regarded as main structural materials of sodium-cooled fast reactors (SFR) and reactor pressure vessel materials of very high temperature reactors (VHTR). The SFR and VHTR systems are designed during long-term duration reaching 60 years at elevated temperatures and often subjected to non-uniform stress and temperature distribution during service. These conditions may generate localized creep damage and propagate the cracks and ultimately may cause a fracture. A significant portion of its life is spent in crack propagation. Therefore, a creep crack growth rate (CCGR) due to creep damage should be assessed for both the base metal (BM) and welded metal (WM). Enough CCGR data for them should be provided for assessing their structural integrities. However, their CCGR data for the Gr. 91 steels is still insufficient. In this study, the CCGR for the BM and the WM of the Gr. 91 steel was comparatively investigated. A series of the CCG tests were conducted under different applied loads for the BM and the WM at 600 .deg. C. The CCGR was characterized in terms of the C parameter, and their CCG behavior were compared, respectively

  20. Variations in creep rate along the Hayward Fault, California, interpreted as changes in depth of creep

    Science.gov (United States)

    Simpson, R.W.; Lienkaemper, J.J.; Galehouse, J.S.

    2001-01-01

    Variations ill surface creep rate along the Hayward fault are modeled as changes in locking depth using 3D boundary elements. Model creep is driven by screw dislocations at 12 km depth under the Hayward and other regional faults. Inferred depth to locking varies along strike from 4-12 km. (12 km implies no locking.) Our models require locked patches under the central Hayward fault, consistent with a M6.8 earthquake in 1868, but the geometry and extent of locking under the north and south ends depend critically on assumptions regarding continuity and creep behavior of the fault at its ends. For the northern onshore part of the fault, our models contain 1.4-1.7 times more stored moment than the model of Bu??rgmann et al. [2000]; 45-57% of this stored moment resides in creeping areas. It is important for seismic hazard estimation to know how much of this moment is released coseismically or as aseismic afterslip.

  1. Diffusional creep and creep degradation in the dispersion-strengthened alloy TD-NiCr

    Science.gov (United States)

    Whittenberger, J. D.

    1972-01-01

    Dispersoid-free regions were observed in TD-NiCr (Ni-20Cr-2ThO2) after slow strain rate testing in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional creep. The net effect of this creep is the degradation of TD-NiCr to a duplex microstructure. Degradation is further enhanced by the formation of voids and integranular oxidation in the thoria-free regions. These regions apparently provided sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20Cr is much less than Ni-20Cr-2ThO2. This localized oxidation does not appear to reduce the static load bearing capacity of TD-NiCr since long stress rupture lives were observed even with heavily oxidized microstructures. But this oxidation does significantly reduce the ductility and impact resistance of the material. Dispersoid-free bands and voids were also observed for two other dispersion strengthened alloys, TD-NiCrAl and IN-853. Thus, it appears that diffusional creep is charactertistic of dispersion-strengthened alloys and can play a major role in the creep degradation of these materials.

  2. Boron effects on creep rupture strength of W containing advanced ferritic creep resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Mito, N.; Hasegawa, Y. [Tohoku Univ., Sendai (Japan)

    2010-07-01

    The creep strength in ferritic creep resistant steels is increased by boron addition. However, the strengthening mechanisms have not yet been studied. This study clarifies the strengthening mechanism of 9% chromium steels with 10{proportional_to}100ppm boron and 0.5{proportional_to}2.0mass% tungsten in the laboratory. The strengthening effect of simultaneous addition of boron and tungsten was analyzed by hardenability, room-temperature strength and creep tests at 650 C. Changes in the microstructure as a result of the addition of boron and tungsten were also examined by optical microscope and transmission electron microscope (TEM). In addition, Alpha-ray Track Etching (ATE) method was used to detect the boron distribution and analyze the mechanisms change in the mechanical properties. Boron addition did not affect room-temperature strength, however, simultaneous addition of boron and tungsten increased room-temperature and high-temperature strength. According to ATE analysis, boron exists at the grain boundary. Therefore, synergistic effects of boron and tungsten on the creep strength suggest the tungsten precipitates stabilization by boron at the grain boundary. (orig.)

  3. Social imaginaries and inclusion

    DEFF Research Database (Denmark)

    Hansen, Janne Hedegaard

    2016-01-01

    The main goal of this entry is to introduce inclusion as a sociological concept consistent with which exclusion is an internal part of inclusion. When exclusion is the basis of inclusion, the establishment of communities will always involve both inclusion and exclusion processes. Similarly......, the development of inclusive schools and inclusive learning environments will involve both inclusion and exclusion processes. With this starting point, international educational research knowledge about inclusive schools and inclusive learning environments in general will be related to the fundamental dilemma...... that inclusion on the one hand may be seen to be about human rights, solidarity, and democracy, and on the other hand, it is about ensuring the cohesion of neoliberal society by means of every person’s obligation to realize one’s potential through learning, development, and education regardless of one’s needs...

  4. Creep, fatigue and creep-fatigue interactions in modified 9% Chromium - 1% Molybdenum (P91) steels

    Science.gov (United States)

    Kalyanasundaram, Valliappa

    Grade P91 steel, from the class of advanced high-chrome ferritic steels, is one of the preferred materials for many elevated temperature structural components. Creep-fatigue (C-F) interactions, along with oxidation, can accelerate the kinetics of damage accumulation and consequently reduce such components' life. Hence, reliable C-F test data is required for meticulous consideration of C-F interactions and oxidation, which in turn is vital for sound design practices. It is also imperative to develop analytical constitutive models that can simulate and predict material response under various long-term in-service conditions using experimental data from short-term laboratory experiments. Consequently, the major objectives of the proposed research are to characterize the creep, fatigue and C-F behavior of grade P91 steels at 625 C and develop robust constitutive models for simulating/predicting their microstructural response under different loading conditions. This work will utilize experimental data from 16 laboratories worldwide that conducted tests (creep, fatigue and C-F) on grade P91 steel at 625°C in a round-robin (RR) program. Along with 7 creep deformation and rupture tests, 32 pure fatigue and 46 C-F tests from the RR are considered in this work. A phenomenological constitutive model formulated in this work needs just five fitting parameters to simulate/predict the monotonic, pure fatigue and C-F behavior of grade P91 at 625 C. A modified version of an existing constitutive model is also presented for particularly simulating its isothermal creep deformation and rupture behavior. Experimental results indicate that specimen C-F lives, as measured by the 2% load drop criterion, seem to decrease with increasing strain ranges and increasing hold times at 625°C. Metallographic assessment of the tested specimens shows that the damage mode in both pure fatigue and 600 seconds hold time cyclic tests is predominantly transgranular fatigue with some presence of

  5. Index of Financial Inclusion

    OpenAIRE

    Mandira Sarma

    2008-01-01

    The promotion of an inclusive financial system is considered a policy priority in many countries. While the importance of financial inclusion is widely recognized, the literature lacks a comprehensive measure that can be used to measure the extent of financial inclusion across economies. This paper attempts to fill this gap by proposing an index of financial inclusion (IFI). The IFI is a multi-dimensional index that captures information on various dimensions of financial inclusion in one sing...

  6. Study of irradiation creep of vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, H.; Strain, R.V.; Smith, D.L. [Argonne National Lab., IL (United States)] [and others

    1997-08-01

    Thin-wall tubing was produced from the 832665 (500 kg) heat of V-4 wt.% Cr-4 wt.% Ti to study its irradiation creep behavior. The specimens, in the form of pressurized capsules, were irradiated in Advanced Test Reactor and High Flux Isotope Reactor experiments (ATR-A1 and HFIR RB-12J, respectively). The ATR-A1 irradiation has been completed and specimens from it will soon be available for postirradiation examination. The RB-12J irradiation is not yet complete.

  7. Revisiting Creeping Competences in the EU

    DEFF Research Database (Denmark)

    Citi, Manuele

    2014-01-01

    case where secondary legislation was employed to extend a formal treaty-based competence (civilian research and technology policy) to an area that, for historical and strategic reasons, has always been a policy monopoly of national governments: research and technology development policy for security...... and defence. Through the analysis of a large pool of documentary data, I elaborate a set of linked hypotheses about the empirical dynamics of creeping competences, and show how the theory of incomplete contracting is best suited to explain this phenomenon....

  8. Jojoba could stop the desert creep

    Energy Technology Data Exchange (ETDEWEB)

    1982-03-25

    The Sahara desert is estimated to be expanding at a rate of 5km a year. The Sudanese government is experimenting with jojoba in six different regions as the bush has the potential to stop this ''desert creep''. The plant, a native to Mexico, is long known for its resistance to drought and for the versatile liquid wax that can be extracted from its seeds. It is estimated that one hectare of mature plants could produce 3000 kg of oil, currently selling at $50 per litre, and so earn valuable foreign currency.

  9. Crack barriers improve the mechanical and thermal properties of non-metallic sinter materials

    Science.gov (United States)

    Gruenthaler, K. H.; Heinrich, W.; Janes, S.; Nixdorf, J.

    1979-01-01

    Means of improving the tensile strength of ceramic composites by introducing ductile intermediate layers capable of absorbing the elastic energy at the rupture front are studied. Tests with an Al203 laminate with niobium inclusions showed that crack propagation could be successfully precluded by dissipation of the energy by deformation and/or delamination at the inclusion/matrix interface.

  10. Accelerated Creep Testing of High Strength Aramid Webbing

    Science.gov (United States)

    Jones, Thomas C.; Doggett, William R.; Stnfield, Clarence E.; Valverde, Omar

    2012-01-01

    A series of preliminary accelerated creep tests were performed on four variants of 12K and 24K lbf rated Vectran webbing to help develop an accelerated creep test methodology and analysis capability for high strength aramid webbings. The variants included pristine, aged, folded and stitched samples. This class of webbings is used in the restraint layer of habitable, inflatable space structures, for which the lifetime properties are currently not well characterized. The Stepped Isothermal Method was used to accelerate the creep life of the webbings and a novel stereo photogrammetry system was used to measure the full-field strains. A custom MATLAB code is described, and used to reduce the strain data to produce master creep curves for the test samples. Initial results show good correlation between replicates; however, it is clear that a larger number of samples are needed to build confidence in the consistency of the results. It is noted that local fiber breaks affect the creep response in a similar manner to increasing the load, thus raising the creep rate and reducing the time to creep failure. The stitched webbings produced the highest variance between replicates, due to the combination of higher local stresses and thread-on-fiber damage. Large variability in the strength of the webbings is also shown to have an impact on the range of predicted creep life.

  11. Out-of-pile creep behavior of uranium carbide

    Science.gov (United States)

    Wright, T. R.; Seltzer, M. S.

    1974-01-01

    Compression creep tests were investigated on various UC-based fuel materials having a variation in both density and composition. Specimens were prepared by casting and by hot pressing. Steady-state creep rates were measured under vacuum at 1400 to 1800 C in the stress range 500-4000 psi.

  12. Mullite—corundum Refractories with High Creep Resistance

    Institute of Scientific and Technical Information of China (English)

    LIANGYong-be; LINan; 等

    1996-01-01

    Mullite-corundum bricks and kiln furni-ture with high creep resistance and good thermal shock resistance were fabricated based on low cost raw materials,the approaches of introducing some additives and optimisig,chemical composition and partical size were mployed to produce a high temperature matrix phase with high creep resistance and good thermal shock resistance.

  13. Creep behavior of abaca fibre reinforced composite material

    Energy Technology Data Exchange (ETDEWEB)

    Tobias, B.C.; Lieng, V.T. [Victoria Univ. of Technology, Victoria (Australia)

    1996-12-31

    This study investigates the creep behavior of abaca fibre reinforced composite lamina. The optimum proportions of constituents and loading conditions, temperature and stresses, are investigated in terms of creep properties. Lamina with abaca fibre volume fractions of 60, 70 and 80 percent, embedded in polyester resin were fabricated. Creep tests in tension at three temperature levels 20{degrees}C, 100{degrees}C and 120{degrees}C and three constant stress levels of 0. 1 MPa, 0. 13 Mpa and 0. 198 MPa using a Dynamic Mechanical Analyzer (DMA) were performed. The creep curves show standard regions of an ideal creep curve such as primary and secondary creep stage. The results also show that the minimum creep rate of abaca fibre reinforced composite increases with the increase of temperature and applied stress. Plotting the minimum creep rate against stress, depicts the variations of stress exponents which vary from 1.6194 at 20{degrees}C to 0.4576 at 120{degrees}C.

  14. Creep degradation in oxide-dispersion-strengthened alloys

    Science.gov (United States)

    Whittenberger, J. D.

    1977-01-01

    Oxide dispersion strengthened Ni-base alloys in wrought bar form are studied for creep degradation effects similar to those found in thin gage sheet. The bar products evaluated included ODS-Ni, ODS-NiCr, and three types of advanced ODS-NiCrAl alloys. Tensile test specimens were exposed to creep at various stress levels at 1365 K and then tensile tested at room temperature. Low residual tensile properties, change in fracture mode, the appearance of dispersoid-free bands, grain boundary cavitation, and internal oxidation in the microstructure were interpreted as creep degradation effects. This work showed that many ODS alloys are subject to creep damage. Degradation of tensile properties occurred after very small amounts of creep strain, ductility being the most sensitive property. All the ODS alloys which were creep damaged possessed a large grain size. Creep damage appears to have been due to diffusional creep which produced dispersoid-free bands around boundaries acting as vacancy sources. Low angle and possibly twin boundaries acted as vacancy sources.

  15. A Comparison of the Irradiation Creep Behavior of Several Graphites

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, Timothy D [ORNL; Windes, Will [Idaho National Laboratory (INL)

    2016-01-01

    Graphite creep strain data from the irradiation creep capsule Advanced Graphite Creep-1 (AGC-1) are reported. This capsule was the first (prototype) of a series of five or six capsules planned as part of the AGC experiment, which was designed to fully characterize the effects of neutron irradiation and the radiation creep behavior of current nuclear graphite. The creep strain data and analysis are reported for the six graphite grades incorporated in the capsule. The AGC-1 capsule was irradiated in the Advanced Test Reactor at Idaho National Laboratory (INL) at approximately 700 C and to a peak dose of 7 dpa (displacements per atom). The specimen s final dose, temperature, and stress conditions have been reported by INL and were used during this analysis. The derived creep coefficients (K) were calculated for each grade and were found to compare well to literature data for the creep coefficient, even under the wide range of AGC-1 specimen temperatures. Comparisons were made between AGC-1 data and historical grade data for creep coefficients.

  16. ON INTEGRITY ASSESSMENT OF AXISYMMETRIC COMPONENTS OPERATING WITHIN CREEP REGIME

    Institute of Scientific and Technical Information of China (English)

    ZARRABI K; LAWRENCE Ng

    2006-01-01

    A multiaxial paradigm for predicting creep damage/lives of components is described. Although in principle the paradigm is general, it is verified using axisymmetric experimental data. It is shown that the proposed paradigm is capable of predicting creep lives with an error of less than 2%. It is also shown that the proposed paradigm is more accurate than the reference stress method.

  17. Creep deformation and rupture behavior of CLAM steel at 823 K and 873 K

    Science.gov (United States)

    Zhong, Boyu; Huang, Bo; Li, Chunjing; Liu, Shaojun; Xu, Gang; Zhao, Yanyun; Huang, Qunying

    2014-12-01

    China Low Activation Martensitic (CLAM) steel is selected as the candidate structural material in Fusion Design Study (FDS) series fusion reactor conceptual designs. The creep property of CLAM steel has been studied in this paper. Creep tests have been carried out at 823 K and 873 K over a stress range of 150-230 MPa. The creep curves showed three creep regimes, primary creep, steady-state creep and tertiary creep. The relationship between minimum creep rate (ε˙min) and the applied stress (σ) could be described by Norton power law, and the stress exponent n was decreased with the increase of the creep temperature. The creep mechanism was analyzed with the fractographes of the rupture specimens which were examined by scanning electron microscopy (SEM). The coarsening of precipitates observed with transmission electron microscope (TEM) indicated the microstructural degradation after creep test.

  18. Effect of misalignment on mechanical behavior of metals in creep. [computer programs

    Science.gov (United States)

    Wu, H. C.

    1979-01-01

    Application of the endochronic theory of viscoplasticity to creep, creep recovery, and stress relaxation at the small strain and short time range produced the following results: (1) The governing constitutive equations for constant-strain-rate stress-strain behavior, creep, creep recovery, and stress relaxation were derived by imposing appropriate constraints on the general constitutive equation of the endochronic theory. (2) A set of material constants was found which correlate strain-hardening, creep, creep recovery, and stress relaxation. (3) The theory predicts with reasonable accuracy the creep and creep recovery behaviors at short time. (4) The initial strain history prior to the creep stage affects the subsequent creep significantly. (5) A critical stress was established for creep recovery. A computer program, written for the misalignment problem is reported.

  19. Experimental Research on Creep Characteristics of Nansha Soft Soil

    Directory of Open Access Journals (Sweden)

    Qingzi Luo

    2014-01-01

    Full Text Available A series of tests were performed to investigate the creep characteristics of soil in interactive marine and terrestrial deposit of Pearl River Delta. The secondary consolidation test results show that the influence of consolidation pressure on coefficient of secondary consolidation is conditional, which is decided by the consolidation state. The ratio of coefficient of secondary consolidation and coefficient of compressibility Ca/Cc is almost a constant, and the value is 0.03. In the shear-box test, the direct sheer creep failure of soil is mainly controlled by shear stress rather than the accumulation of shear strain. The triaxial creep features are closely associated with the drainage conditions, and consolidation can weaken the effect of creep. When the soft soil has triaxial creep damage, the strain rate will increase sharply.

  20. Optimum design of inhomogeneous rotating discs under secondary creep

    Energy Technology Data Exchange (ETDEWEB)

    Farshi, Behrooz [Department of Mechanical Engineering, Iran University of Science and Technology, Tehran 16846 (Iran, Islamic Republic of)], E-mail: Farshi@iust.ac.ir; Bidabadi, Jalal [Department of Mechanical Engineering, Iran University of Science and Technology, Tehran 16846 (Iran, Islamic Republic of)

    2008-07-15

    Rotating discs commonly used in the aerospace industry often operate under high mechanical stresses due to centrifugal forces, while subject to high temperature gradients. High stresses and temperatures lead to creep in such rotating disc applications. This problem is particularly important in turbine discs under continuous operation. Since such discs are subject to secondary creep effects during most of their useful lives, it is important that they be optimized for minimum weight for the steady-state creep stresses. In this investigation, by considering the variable physical properties of the rotating disc materials under a high temperature gradient, a procedure for weight minimization for the steady-state creep stresses is proposed. The method aims to design the disc thickness profile so as to have minimum weight while the equivalent secondary creep stresses of the rotating disc under a high temperature gradient at all points simultaneously approach but do not exceed an allowable stress. An example is given to illustrate the method.

  1. Accelerated creep of Ni-YSZ anodes during reduction

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Greco, Fabio; Ni, De Wei

    2014-01-01

    by the thermomechanical history of the stack (e.g. sintering temperature, time at temperature etc.). During operation the stress state will depend on time as stresses are relaxed by creep processes. Creep has mainly been studied at operating conditions, where the Ni-YSZ anode is in the reduced state and YSZ is the main...... load-carrying component. In this work we report on a new creep-reduction phenomenon observed to take place during the reduction process itself, where stresses are relaxed at a rate much faster (~×104) than during operation where the anode is in fully reduced state. Furthermore, samples exposed...... to a very small tensile stress (0.004 MPa) were observed to expand during reduction, which is in contrast with reports in literature [Ref].The “accelerated” creep has a tremendous impact on the stress field in an operating SOFC stack. Creep experiments, where carried out on NiO-YSZ anode support structures...

  2. Uniaxial tension and tensile creep behaviors of EPS

    Institute of Scientific and Technical Information of China (English)

    康颖安; 李显方; 谭加才

    2008-01-01

    The mechanical behavior of EPS(Expanded polystyrene) with three densities at room temperature and under tension loading was studied.The results show that EPS material is characterized by brittle behavior in the tension tests,and tensile properties of EPS increase with the increase of density.Volume fraction has no a significant effect on the modulus of these foams.The tensile creep strain increases with stress for EPS with same density,indicating that the creep behavior is of the stress dependency.And the creep behavior of EPS exhibits density dependency,which the creep strain decreases with densities for a fixed stress value.Moreover the creep behavior under the constant tension load is well in coincidence with the three-parameter solid model.

  3. Creep in refractory materials; Fluencia en materiales refractarios

    Energy Technology Data Exchange (ETDEWEB)

    Tomba Martinez, A. G.; Luz, A. P.; Pandolfelli, V. C.

    2013-10-01

    Refractory materials are widely used in various industrial fields due to their outstanding properties and performance in aggressive environments. However, although creep resistance is one of the most important properties for the selection of these materials, few researches were carried out focused on the fundamentals and technological understanding of their performance at high temperatures. In this context, this work addresses: 1) the creep mechanisms, 2) the mathematical models proposed for the analysis and to forecast the creep deformation at high temperature, 3) technical procedures and experimental testing, and 4) a critical analysis of some basic and practical aspects considering the literature available on this issue. Based on the collected information, mathematical models (such as the Projection concept) were considered as a powerful tool for the prediction of the refractories creep behavior, helping to identify the main creep mechanisms in these materials and to induce the development of optimized compositions able to attend the end-users requirements. (Author)

  4. Indentation creep in zirconia ceramics under variable loads

    Energy Technology Data Exchange (ETDEWEB)

    Ren, X.J. [School of Engineering, Liverpool John Moores Univ., Liverpool (United Kingdom); Hooper, R.M. [School of Engineering and Computer Science, Univ. of Exeter, Exeter (United Kingdom); Henshall, J.L. [Mechanical and Mfg. Engineering Dept., Nottingham Trent Univ., Nottingham (United Kingdom)

    2005-07-01

    Time dependent deformation at room and elevated temperature is a significant property of zirconia ceramics and has a direct influence on their use. An understanding of this time dependent behaviour is therefore important in predicting the service life of a component. In this work, the indentation creep behaviour of two typical zirconia ceramics - ceria stabilised polycrystalline tetragonal (Ce-TZP) and yttria (6%) stabilized polycrystalline cubic zirconia, YCPZ, have been investigated from room temperature to 600 C. Indentation creep tests with various loads yielded identical creep rate, which indicates that indentation size effect has no significant effect on the indentation creep of zirconia ceramics. Tests with variable loads, using a spring loaded apparatus, exhibited comparable indentation creep rates to that under constant loading. (orig.)

  5. Dislocation-mediated creep process in nanocrystalline Cu

    Institute of Scientific and Technical Information of China (English)

    Mu Jun-Wei; Sun Shi-Cheng; Jiang Zhong-Hao; Lian Jian-She; Jiang Qing

    2013-01-01

    Nanocrystalline Cu with average grain sizes ranging from ~ 24.4 to 131.3 nm were prepared by the electric brushplating technique.Nanoindentation tests were performed within a wide strain rate range,and the creep process of nanocrystalline Cu during the holding period and its relationship to dislocation and twin structures were examined.It was demonstrated that creep strain and creep strain rate are considerably significant for smaller grain sizes and higher loading strain rates,and are far higher than those predicted by the models of Cobble creep and grain boundary sliding.The analysis based on the calculations and experiments reveals that the significant creep deformation arises from the rapid absorption of high density dislocations stored in the loading regime.Our experiments imply that stored dislocations during loading are highly unstable and dislocation activity can proceed and lead to significant post-loading plasticity.

  6. Creep damage development in welded X20 and P91

    Energy Technology Data Exchange (ETDEWEB)

    Brett, Steve; Holmstrom, Stefan; Hald, John; Borg, Ulrik; Aakjaer Jensen, Soeren; Vulpen, Rijk Van; Degnan, Craig; Vinter Dahl, Kristian; Vilhelmsen, Tommy

    2011-03-15

    The Martensitic steel X20CrMoV121 (hereinafter called X20) and the modified 9Cr1Mo steel (hereinafter called P91) have been used for a number of years in high temperature applications since they posses superior creep strength compared to low alloyed steels. Due to the simple fact that very few failures were observed, almost no knowledge as to the evolution of creep damage in welds were available despite long operation times exceeding well over 100.000 hours. It has been suggested that X20 will develop creep damage in a different manner compared to low alloyed steel, i.e damage initiation should be slow followed by accelerated growth. The research work presented in this report included systematic investigations of the first components of X20, which has developed creep during long-term operation. All of the investigated components showed creep damage evolution similar to low alloy steels

  7. Determination of the Creep Parameters of Linear Viscoelastic Materials

    Directory of Open Access Journals (Sweden)

    Alibay Iskakbayev

    2016-01-01

    Full Text Available Creep process of linear viscoelastic materials is described by the integral equation of Boltzmann-Volterra in which creep kernel is approximated by Rabotnov’s fractional exponential function. The creep equation contains four unknown parameters: α, singularity parameter; β, fading parameter; λ, rheological parameter; and ε0, conditionally instantaneous strain. Two-stage determination method of creep parameters is offered. At the first stage, taking into account weak singularity properties of Abel’s function at the initial moment of loading, parameters ε0 and α are determined. At the second stage, using already known parameters ε0 and α, parameters β and λ are determined. Analytical expressions for calculating these parameters are obtained. An accuracy evaluation of the offered method with using experimentally determined creep strains of material Nylon 6 and asphalt concrete showed its high accuracy.

  8. A New Creep Constitutive Model for 7075 Aluminum Alloy Under Elevated Temperatures

    Science.gov (United States)

    Lin, Y. C.; Jiang, Yu-Qiang; Zhou, Hua-Min; Liu, Guan

    2014-12-01

    Exposure of aluminum alloy to an elastic loading, during "creep-aging forming" or other manufacturing processes at relatively high temperature, may lead to the lasting creep deformation. The creep behaviors of 7075 aluminum alloy are investigated by uniaxial tensile creep experiments over wide ranges of temperature and external stress. The results show that the creep behaviors of the studied aluminum alloy strongly depend on the creep temperature, external stress, and creep time. With the increase of creep temperature and external stress, the creep strain increases quickly. In order to overcome the shortcomings of the Bailey-Norton law and θ projection method, a new constitutive model is proposed to describe the variations of creep strain with time for the studied aluminum alloy. In the proposed model, the dependences of creep strain on the creep temperature, external stress, and creep time are well taken into account. A good agreement between the predicted and measured creep strains shows that the established creep constitutive model can give an accurate description of the creep behaviors of 7075 aluminum alloy. Meanwhile, the obtained stress exponent indicates that the creep process is controlled by the dislocation glide, which is verified by the microstructural observations.

  9. Study of creep cavity growth for power plant lifetime assessment

    Energy Technology Data Exchange (ETDEWEB)

    Wu Rui; Sandstroem, Rolf

    2001-01-01

    This report aims to the sub project lifetime assessment by creep (livslaengdspredikteringar vid kryp), which is involved in the project package strength in high temperature power plant, KME 708. The physical creep damage includes mainly cavities and their development. Wu and Sandstroem have observed that cavity size increases linearly with increasing creep strain in a 12%Cr steel. Sandstroem has showed that, based on the relations between the nucleation and growth of creep cavities with creep strain, the physical creep damage can be modelled as a function of creep strain. In the present paper the growth of creep cavity radius R in relation to time t and strain {epsilon} in low alloy and 12%Cr steels as well as a Type 347 steel has been studied. The results exhibit that the power law cavity radius with creep time (R-t) and with creep strain (R-{epsilon}) relations are found for these materials at various testing conditions. The power law R-t and R-{epsilon} relations are in most cases dependent and independent on testing conditions, respectively. The empirical power law R-{epsilon} relations give a description of cavity evolution, which can be used for lifetime assessment. Experimental data have also been compared to the estimations by the classical models for cavity growth, including the power law growth due to Hancock, the diffusion growth due to Speight and Harris, the constrained diffusion growths due to Dyson and due to Rice and the enhanced diffusion growth due to Beere. It appears that the constraint diffusion growth models give a reasonable estimation of R-{epsilon} relation in many cases. The diffusion growth model is only applicable for limited cases where the power over t in R-t relation takes about 1/3. The power law and the enhanced diffusion models are found in most cases to overestimate the cavity growth.

  10. Analysis of Multistage and Other Creep Data for Domal Salts

    Energy Technology Data Exchange (ETDEWEB)

    Munson, D.E.

    1998-10-01

    There have existed for some time relatively sparse creep databases for a number of domal salts. Although all of these data were analyzed at the time they were reported, to date there has not been a comprehensive, overall evaluation within the same analysis framework. Such an evaluation may prove of value. The analysis methodology is based on the Multimechanism Deformation (M-D) description of salt creep and the corresponding model parameters determined from conventional creep tests. The constitutive model of creep wss formulated through application of principles involved in micromechanical modeling. It was possible, at minimum, to obtain the steady state parameters of the creep model from the data on the domal salts. When this was done, the creep of the domal salts, as compared to the well-defined Waste Isolation Pilot Plant (WIPP) bedded clean salt, was either essentially identical to, or significantly harder (more creep resistant) than WIPP salt. Interestingly, the domal salts form two distinct groups, either sofl or hard, where the difference is roughly a factor often in creep rate between the twcl groups. As might be expected, this classification corresponds quite well to the differences in magnitude of effective creep volume losses of the Strategic Petroleum Reserve (SPR) caverns as determined by the CAVEMAN cavern pressure history analysis, depending upon the specific dome or region within the dome. Creep response shoulcl also correlate to interior cavern conditions that produce salt falls. WMle, in general, the caverns in hard sah have a noticeably greater propensity for salt falls, a smaller number of similar events are exhibited even in the caverns in soft salt.

  11. Addition of chromic oxide to creep feed as a fecal marker for selection of creep feed-eating suckling pigs

    NARCIS (Netherlands)

    Kuller, W.I.; Beers-Schreurs, van H.M.G.; Soede, N.M.; Taverne, M.A.M.; Kemp, B.; Verheijden, J.H.M.

    2007-01-01

    Objective-To determine whether the addition of chromic oxide (Cr2O3) to creep feed could be used as a visual marker in feces for selection of creep feed-eating suckling pigs. Animals-20 suckling pigs. Procedures-Via syringe, 5 pigs (2 to 3 days old on day 0; 1 pig/treatment) from each of 4 litters

  12. Addition of chromic oxide to creep feed as a fecal marker for selection of creep feed-eating suckling pigs

    NARCIS (Netherlands)

    Kuller, W.I.; Beers-Schreurs, van H.M.G.; Soede, N.M.; Taverne, M.A.M.; Kemp, B.; Verheijden, J.H.M.

    2007-01-01

    Objective-To determine whether the addition of chromic oxide (Cr2O3) to creep feed could be used as a visual marker in feces for selection of creep feed-eating suckling pigs. Animals-20 suckling pigs. Procedures-Via syringe, 5 pigs (2 to 3 days old on day 0; 1 pig/treatment) from each of 4 litters r

  13. The nonunjform distribution of inclusions in low-alloy steel weld deposits

    Science.gov (United States)

    Sugden, A. A. B.; Bhadeshia, H. K. D. H.

    1988-03-01

    Nonmetallic inclusions in low-alloy steel welds have an important effect on the microstructure and properties of weld deposits. This work is an attempt at understanding the factors controlling the spatial distribution of such inclusions, with particular emphasis on the uniformity of the distribution and the effect of solidification mode during manual-metal-arc welding. The solidification mode has been controlled by using unusual combinations of base plates and experimental electrodes. It is found that the first phase to solidify (in the form of columnar grains) is delta-ferrite ( δ) when a medium carbon electrode is deposited onto a low carbon substrate, but that it is austenite ( γ) when a low carbon electrode is deposited onto a high carbon substrate. Relatively large inclusions have been found to position themselves preferentially, during solidification, to the columnar grain boundaries of the first phase to solidify, whether this is 8-ferrite or austenite. The results can be understood qualitatively in terms of a surface tension driven Marangoni effect, or in terms of the pushing of solid inclusions by the solidification front. Both mechanisms drive the larger inclusions into cusps in the interface while smaller ones are passively trapped. The implications of the observed nonuniform distribution of inclusions are more severe for solidification with austenite as the primary phase, since the larger inclusions are in that case located in the weakest region of the weld where they also do not contribute to the intragranular nucleation of acicular ferrite.

  14. Recycling of non-metallic fractions from waste electrical and electronic equipment (WEEE): a review.

    Science.gov (United States)

    Wang, Ruixue; Xu, Zhenming

    2014-08-01

    The world's waste electrical and electronic equipment (WEEE) consumption has increased incredibly in recent decades, which have drawn much attention from the public. However, the major economic driving force for recycling of WEEE is the value of the metallic fractions (MFs). The non-metallic fractions (NMFs), which take up a large proportion of E-wastes, were treated by incineration or landfill in the past. NMFs from WEEE contain heavy metals, brominated flame retardant (BFRs) and other toxic and hazardous substances. Combustion as well as landfill may cause serious environmental problems. Therefore, research on resource reutilization and safe disposal of the NMFs from WEEE has a great significance from the viewpoint of environmental protection. Among the enormous variety of NMFs from WEEE, some of them are quite easy to recycle while others are difficult, such as plastics, glass and NMFs from waste printed circuit boards (WPCBs). In this paper, we mainly focus on the intractable NMFs from WEEE. Methods and technologies of recycling the two types of NMFs from WEEE, plastics, glass are reviewed in this paper. For WEEE plastics, the pyrolysis technology has the lowest energy consumption and the pyrolysis oil could be obtained, but the containing of BFRs makes the pyrolysis recycling process problematic. Supercritical fluids (SCF) and gasification technology have a potentially smaller environmental impact than pyrolysis process, but the energy consumption is higher. With regard to WEEE glass, lead removing is requisite before the reutilization of the cathode ray tube (CRT) funnel glass, and the recycling of liquid crystal display (LCD) glass is economically viable for the containing of precious metals (indium and tin). However, the environmental assessment of the recycling process is essential and important before the industrialized production stage. For example, noise and dust should be evaluated during the glass cutting process. This study could contribute

  15. Peat and its modification products as sorbents for remeval of metals, metalloids and nonmetallic elements

    Science.gov (United States)

    Klavins, Maris; Ansone, Linda; Robalds, Artis; Dudare, Diana

    2013-04-01

    For remediation of soils and purification of waters biosorbents might be considered as an prospective group of materials and amongst them peat have a special role due to low cost, biodegradability, high number of functional groups, well developed surface area and combination of hydrophilic/hydrophobic structural elements. We have demonstrated the possibilities to use peat and its thermal treatment products for oil sorption. Peat as an oil sorbent has poor buoyancy characteristics, relatively low oil sorption capacity and low hydrophobicity. However, thermal treatment (low-temperature pyrolysis and synthesis of peat-based active coal) helps to significantly improve its sorptive characteristics. The processes and structural changes taking place during low-temperature pyrolysis have been studied by means of IR spectroscopy, thermogravimetry and scanning electron microscopy. Peat can be used also as an efficient sorbent for sorption of metallic elements as it has been demonstrated on example of Tl+, Cu2+, Cr3+, however sorption capacity in respect to nonmetallic (anionic species) elements is low. To develop such application possibilities peat, peat modified with iron compounds, iron humates were prepared and tested for sorption of arsenic and phosphorous compounds in comparison with weakly basic anionites. The highest sorption capacity was observed when peat sorbents modified with iron compounds were used. Sorption of different arsenic speciation forms onto iron-modified peat sorbents was investigated as a function of pH and temperature. It was established that sorption capacity increases with a rise in temperature, and the calculation of sorption process thermodynamic parameters indicates the spontaneity of sorption process and its endothermic nature.

  16. Diffusion creep in the mantle may create and maintain anisotropy

    Science.gov (United States)

    Wheeler, John

    2014-05-01

    Diffusion creep is thought to play an important role in lower mantle deformation and hence must be understood in detail if Earth behaviour is to be explained. It is commonly claimed that diffusion creep gives rise to equant grain shapes and destroys any crystallographic preferred orientation (CPO), so all physical properties would be isotropic. Some experiments on olivine support the first assertion but other minerals, and polyphase rocks, commonly show inequant grain shapes in nature and experiment even when diffusion creep is thought to be a major contribution to strain. Numerical models allow rigorous exploration of the effects of deformation under conditions not easily reached in experiments. A numerical model named 'DiffForm' (Wheeler & Ford 2007) gives insight into how grain shapes and microstructures evolve during diffusion creep. Modelling shows that whilst grains may initially rotate in apparently chaotic fashion during diffusion creep, such rotations slow down as grains become inequant. Consequently, an initial CPO (formed, for example, by dislocation creep at higher strain rates) will be decreased in intensity but not destroyed. Seismic anisotropy will decrease but not disappear (Wheeler 2009). Diffusion creep is also predicted to have intense mechanical anisotropy. In simple models diffusion creep is controlled entirely by diffusion and sliding along grain boundaries; there is no crystallographic influence. An aggregate of equant grains must then be mechanically isotropic, but a model microstructure with inequant grains has marked mechanical anisotropy (Wheeler 2010) - an effect related to the fact that grain boundary sliding is an intrinsic part of diffusion creep. That work was based on a very simple microstructure with a single inequant grain shape but I present here new results showing that for more complicated microstructures, mechanical anisotropy is intense even for quite modest grain elongations. There will be feedback between strain and

  17. Creep and Creep-Fatigue Crack Growth at Structural Discontinuities and Welds

    Energy Technology Data Exchange (ETDEWEB)

    Dr. F. W. Brust; Dr. G. M. Wilkowski; Dr. P. Krishnaswamy; Mr. Keith Wichman

    2010-01-27

    The subsection ASME NH high temperature design procedure does not admit crack-like defects into the structural components. The US NRC identified the lack of treatment of crack growth within NH as a limitation of the code and thus this effort was undertaken. This effort is broken into two parts. Part 1, summarized here, involved examining all high temperature creep-fatigue crack growth codes being used today and from these, the task objective was to choose a methodology that is appropriate for possible implementation within NH. The second part of this task, which has just started, is to develop design rules for possible implementation within NH. This second part is a challenge since all codes require step-by-step analysis procedures to be undertaken in order to assess the crack growth and life of the component. Simple rules for design do not exist in any code at present. The codes examined in this effort included R5, RCC-MR (A16), BS 7910, API 579, and ATK (and some lesser known codes). There are several reasons that the capability for assessing cracks in high temperature nuclear components is desirable. These include: (1) Some components that are part of GEN IV reactors may have geometries that have sharp corners - which are essentially cracks. Design of these components within the traditional ASME NH procedure is quite challenging. It is natural to ensure adequate life design by modeling these features as cracks within a creep-fatigue crack growth procedure. (2) Workmanship flaws in welds sometimes occur and are accepted in some ASME code sections. It can be convenient to consider these as flaws when making a design life assessment. (3) Non-destructive Evaluation (NDE) and inspection methods after fabrication are limited in the size of the crack or flaw that can be detected. It is often convenient to perform a life assessment using a flaw of a size that represents the maximum size that can elude detection. (4) Flaws that are observed using in-service detection

  18. Long-term monitoring of creep rate along the Hayward fault and evidence for a lasting creep response to 1989 Loma Prieta earthquake

    Science.gov (United States)

    Lienkaemper, J.J.; Galehouse, J.S.; Simpson, R.W.

    2001-01-01

    We present results from over 30 yr of precise surveys of creep along the Hayward fault. Along most of the fault, spatial variability in long-term creep rates is well determined by these data and can help constrain 3D-models of the depth of the creeping zone. However, creep at the south end of the fault stopped completely for more than 6 years after the M7 1989 Loma Prieta Earthquake (LPEQ), perhaps delayed by stress drop imposed by this event. With a decade of detailed data before LPEQ and a decade after it, we report that creep response to that event does indeed indicate the expected deficit in creep.

  19. An axisymmetric method of creep analysis for primary and secondary creep

    Energy Technology Data Exchange (ETDEWEB)

    Jahed, Hamid; Bidabadi, Jalal

    2003-09-01

    A general axisymmetric method for elastic-plastic analysis was previously proposed by Jahed and Dubey [ASME J Pressure Vessels Technol 119 (1997) 264]. In the present work the method is extended to the time domain. General rate type governing equations are derived and solved in terms of rate of change of displacement as a function of rate of change in loading. Different types of loading, such as internal and external pressure, centrifugal loading and temperature gradient, are considered. To derive specific equations and employ the proposed formulation, the problem of an inhomogeneous non-uniform rotating disc is worked out. Primary and secondary creep behaviour is predicted using the proposed method and results are compared to FEM results. The problem of creep in pressurized vessels is also solved. Several numerical examples show the effectiveness and robustness of the proposed method.

  20. The Unified Creep-Fatigue Equation for Stainless Steel 316

    Directory of Open Access Journals (Sweden)

    Dan Liu

    2016-09-01

    Full Text Available Background—The creep-fatigue properties of stainless steel 316 are of interest because of the wide use of this material in demanding service environments, such as the nuclear industry. Need—A number of models exist to describe creep-fatigue behaviours, but they are limited by the need to obtain specialized coefficients from a large number of experiments, which are time-consuming and expensive. Also, they do not generalise to other situations of temperature and frequency. There is a need for improved formulations for creep-fatigue, with coefficients that determinable directly from the existing and simple creep-fatigue tests and creep rupture tests. Outcomes—A unified creep-fatigue equation is proposed, based on an extension of the Coffin-Manson equation, to introduce dependencies on temperature and frequency. The equation may be formulated for strain as ε p = C 0 c ( T , t , ε p N − β 0 , or as a power-law ε p = C 0 c ( T , t N − β 0 b ( T , t . These were then validated against existing experimental data. The equations provide an excellent fit to data (r2 = 0.97 or better. Originality—This work develops a novel formulation for creep-fatigue that accommodates temperature and frequency. The coefficients can be obtained with minimum experimental effort, being based on standard rather than specialized tests.

  1. Recent Methodologies for Creep Deformation Analysis and Its Life Prediction

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo-Gon; Park, Jae-Young; Iung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    To design the high-temperature creeping materials, various creep data are needed for codification, as follows: i) stress vs. creep rupture time for base metals and weldments (average and minimum), ii) stress vs. time to 1% total strain (average), iii) stress vs. time to onset of tertiary creep (minimum), and iv) constitutive eqns. for conducting time- and temperature- dependent stress-strain (average), and v) isochronous stress-strain curves (average). Also, elevated temperature components such as those used in modern power generation plant are designed using allowable stress under creep conditions. The allowable stress is usually estimated on the basis of up to 10{sup 5} h creep rupture strength at the operating temperature. The master curve of the “sinh” function was found to have a wider acceptance with good flexibility in the low stress ranges beyond the experimental data. The proposed multi-C method in the LM parameter revealed better life prediction than a single-C method. These improved methodologies can be utilized to accurately predict the long-term creep life or strength of Gen-IV nuclear materials which are designed for life span of 60 years.

  2. Developing Process of Negative Creeping Discharge along Aerial Insulated Wire

    Science.gov (United States)

    Nishi, Toshiyuki; Hanaoka, Ryoichi; Takata, Shinzo

    When a lightning occurs at the neighborhood of high voltage aerial distribution lines, the overvoltage due to the inductive lightning surge invades to the central line of the insulated wire. Because of the insulated wire is supported by the insulator and the binding wire at the electric light pole, the creeping discharges develop along the wire surface from the free end of the binding wire, just after a flashover of the insulator at the wire supporting point. These creeping discharges give rise to the disaster near the wire supporting point including the punch-through breakdown of wire when the weak points such as pin-holes exist in the wire insulator. To prevent these accidents, it is important to understand the behavior of creeping discharges at the insulated wire surface originating in the lightning strike. Positive and negative creeping discharges reveal the distinctive aspect by the polarities of the inductive lightning surges. In the previous paper, we have clarified the developing process of positive creeping discharge based on the data obtained from an image converter camera. In this paper, we report the developing process of negative creeping discharge. Complicated behavior of negative creeping discharge is clarified using an image converter camera and its process is discussed.

  3. Foresighting for Inclusive Development

    DEFF Research Database (Denmark)

    Dahl Andersen, Allan; Andersen, Per Dannemand

    We propose that foresight can contribute to inclusive development by making innovation policy processes more inclusive, which in turn makes innovation systems more inclusive. Processes of developing future-oriented innovation policies are often unsuccessful and rarely inclusive. We conceptualize ...... and processes in two foresight cases in two emerging economies - Brazil and South Korea. Although the research is exploratory and the results tentative, the empirical studies support our main propositions....

  4. Creep-fatigue modelling in structural steels using empirical and constitutive creep methods implemented in a strip-yield model

    Science.gov (United States)

    Andrews, Benjamin J.

    The phenomena of creep and fatigue have each been thoroughly studied. More recently, attempts have been made to predict the damage evolution in engineering materials due to combined creep and fatigue loading, but these formulations have been strictly empirical and have not been used successfully outside of a narrow set of conditions. This work proposes a new creep-fatigue crack growth model based on constitutive creep equations (adjusted to experimental data) and Paris law fatigue crack growth. Predictions from this model are compared to experimental data in two steels: modified 9Cr-1Mo steel and AISI 316L stainless steel. Modified 9Cr-1Mo steel is a high-strength steel used in the construction of pressure vessels and piping for nuclear and conventional power plants, especially for high temperature applications. Creep-fatigue and pure creep experimental data from the literature are compared to model predictions, and they show good agreement. Material constants for the constitutive creep model are obtained for AISI 316L stainless steel, an alloy steel widely used for temperature and corrosion resistance for such components as exhaust manifolds, furnace parts, heat exchangers and jet engine parts. Model predictions are compared to pure creep experimental data, with satisfactory results. Assumptions and constraints inherent in the implementation of the present model are examined. They include: spatial discretization, similitude, plane stress constraint and linear elasticity. It is shown that the implementation of the present model had a non-trivial impact on the model solutions in 316L stainless steel, especially the spatial discretization. Based on these studies, the following conclusions are drawn: 1. The constitutive creep model consistently performs better than the Nikbin, Smith and Webster (NSW) model for predicting creep and creep-fatigue crack extension. 2. Given a database of uniaxial creep test data, a constitutive material model such as the one developed for

  5. Inclusion : Conceptualization and measurement

    NARCIS (Netherlands)

    Jansen, Wiebren S.; Otten, Sabine; van der Zee, Karen I.; Jans, Lise

    In the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal

  6. Inclusion: Conceptualization and measurement

    NARCIS (Netherlands)

    Jansen, W.S.; Otten, S.; Van der Zee, K.I.; Jans, L.

    2014-01-01

    n the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal

  7. Inclusion: Conceptualization and measurement

    NARCIS (Netherlands)

    Jansens, Wiebren S.; Otten, Sabine; van der Zee, Karen; Jans, Lise

    2014-01-01

    In the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal

  8. Inclusive Education in Bangladesh

    Science.gov (United States)

    Ahsan, Mohammad Tariq; Burnip, Lindsay

    2007-01-01

    This article reports on inclusive education in Bangladesh for children with special needs. Bangladesh is not behind other developed countries in enacting laws and declarations in favour of inclusive education, but a lack of resources is the main barrier in implementing inclusive education. Special education and integrated education models exist in…

  9. Footstep towards Inclusive Education

    Science.gov (United States)

    Abbas, Faiza; Zafar, Aneeka; Naz, Tayyaba

    2016-01-01

    Inclusive education is a rising trend in the world. The first step towards inclusive education is providing the awareness to the general education teachers. This study focused to investigate the general education teachers of primary and secondary level awareness about the special education and inclusive education. This study is descriptive method…

  10. Towards Inclusive Schooling

    Science.gov (United States)

    Gafoor, K. Abdul

    2010-01-01

    Social inclusion is the process that will enable every person in society to participate in normal activities of societies they live in, including education, employment, public services and social recreational activities. For the development of an inclusive society, preparation of younger generation also needs to be inclusive. Our schools must…

  11. Inclusion in Middle Tennessee

    Science.gov (United States)

    Salter, Derrick; Ashley, Mandi; Hayes, Brandalyn

    2013-01-01

    The overall purpose of this study was to provide school districts within Tennessee with more research about how weekly hours of inclusion impact student achievement. Specifically, researchers examined which models of inclusion were in use in two school districts in Tennessee, administrators' and teachers' perceptions of inclusion, and whether or…

  12. Inclusion: Conceptualization and measurement

    NARCIS (Netherlands)

    Jansens, Wiebren S.; Otten, Sabine; Zee, van der Karen I.; Jans, Lise

    2014-01-01

    In the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal disti

  13. Inclusion: Conceptualization and measurement

    NARCIS (Netherlands)

    Jansen, W.S.; Otten, S.; Van der Zee, K.I.; Jans, L.

    2014-01-01

    n the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal distin

  14. Inclusion : Conceptualization and measurement

    NARCIS (Netherlands)

    Jansen, Wiebren S.; Otten, Sabine; van der Zee, Karen I.; Jans, Lise

    2014-01-01

    In the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal disti

  15. Creep and Creep-Fatigue Crack Growth at Structural Discontinuities and Welds

    Energy Technology Data Exchange (ETDEWEB)

    Dr. F. W. Brust; Dr. G. M. Wilkowski; Dr. P. Krishnaswamy; Mr. Keith Wichman

    2010-01-27

    The subsection ASME NH high temperature design procedure does not admit crack-like defects into the structural components. The US NRC identified the lack of treatment of crack growth within NH as a limitation of the code and thus this effort was undertaken. This effort is broken into two parts. Part 1, summarized here, involved examining all high temperature creep-fatigue crack growth codes being used today and from these, the task objective was to choose a methodology that is appropriate for possible implementation within NH. The second part of this task, which has just started, is to develop design rules for possible implementation within NH. This second part is a challenge since all codes require step-by-step analysis procedures to be undertaken in order to assess the crack growth and life of the component. Simple rules for design do not exist in any code at present. The codes examined in this effort included R5, RCC-MR (A16), BS 7910, API 579, and ATK (and some lesser known codes). There are several reasons that the capability for assessing cracks in high temperature nuclear components is desirable. These include: (1) Some components that are part of GEN IV reactors may have geometries that have sharp corners - which are essentially cracks. Design of these components within the traditional ASME NH procedure is quite challenging. It is natural to ensure adequate life design by modeling these features as cracks within a creep-fatigue crack growth procedure. (2) Workmanship flaws in welds sometimes occur and are accepted in some ASME code sections. It can be convenient to consider these as flaws when making a design life assessment. (3) Non-destructive Evaluation (NDE) and inspection methods after fabrication are limited in the size of the crack or flaw that can be detected. It is often convenient to perform a life assessment using a flaw of a size that represents the maximum size that can elude detection. (4) Flaws that are observed using in-service detection

  16. Influence of Rare Earth Metals on Microstructure and Inclusions Morphology G17CrMo5-5 Cast Steel

    Directory of Open Access Journals (Sweden)

    Kasińska J.

    2014-10-01

    Full Text Available This paper presents influence of rare earth metals (REM on the microstructure and morphology of non-metallic inclusions of G17CrMo5-5 cast carbon steel The research has been performed on successive industrial melts. Each time about 2000 kg of liquid metal was modified. The REM was in the form of mishmetal of the composition 49, 8% Ce, 21, 8% La, 17, 1% Nd, 5, 5% Pr and 5, 35% the rest of REM. Therareearth metals were put into the ladle during tapping of heat melt from the furnace.

  17. Creep of Two-Phase Microstructures for Microelectronic Applications

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, Heidi Linch [Univ. of California, Berkeley, CA (United States)

    1998-12-01

    The mechanical properties of low-melting temperature alloys are highly influenced by their creep behavior. This study investigates the dominant mechanisms that control creep behavior of two-phase, low-melting temperature alloys as a function of microstructure. The alloy systems selected for study were In-Ag and Sn-Bi because their eutectic compositions represent distinctly different microstructure.” The In-Ag eutectic contains a discontinuous phase while the Sn-Bi eutectic consists of two continuous phases. In addition, this work generates useful engineering data on Pb-free alloys with a joint specimen geometry that simulates microstructure found in microelectronic applications. The use of joint test specimens allows for observations regarding the practical attainability of superplastic microstructure in real solder joints by varying the cooling rate. Steady-state creep properties of In-Ag eutectic, Sn-Bi eutectic, Sn-xBi solid-solution and pure Bi joints have been measured using constant load tests at temperatures ranging from O°C to 90°C. Constitutive equations are derived to describe the steady-state creep behavior for In-Ageutectic solder joints and Sn-xBi solid-solution joints. The data are well represented by an equation of the form proposed by Dom: a power-law equation applies to each independent creep mechanism. Rate-controlling creep mechanisms, as a function of applied shear stress, test temperature, and joint microstructure, are discussed. Literature data on the steady-state creep properties of Sn-Bi eutectic are reviewed and compared with the Sn-xBi solid-solution and pure Bi joint data measured in the current study. The role of constituent phases in controlling eutectic creep behavior is discussed for both alloy systems. In general, for continuous, two-phase microstructure, where each phase exhibits significantly different creep behavior, the harder or more creep resistant phase will dominate the creep behavior in a lamellar microstructure. If a

  18. Deformation and rupture of stainless steel under cyclic, torsional creep

    OpenAIRE

    Rees, DWA

    2008-01-01

    Copyright 2008 @ Engineering Integrity Society. Recent results from a long-term, strain-limited, cyclic creep test program upon stainless steel tubes are given. The test conditions employed were: constant temperature 500 °C, shear stress Ƭ = ± 300 MPa and shear strain limits ƴ = ± 4%. It is believed that a cyclic creep behaviour for the material has been revealed that has not been reported before in the literature. That is, the creep curves for stainless steel under repeated, shear stress...

  19. Predicting dislocation climb and creep from explicit atomistic details.

    Science.gov (United States)

    Kabir, Mukul; Lau, Timothy T; Rodney, David; Yip, Sidney; Van Vliet, Krystyn J

    2010-08-27

    Here we report kinetic Monte Carlo simulations of dislocation climb in heavily deformed, body-centered cubic iron comprising a supersaturation of vacancies. This approach explicitly incorporates the effect of nonlinear vacancy-dislocation interaction on vacancy migration barriers as determined from atomistic calculations, and enables observations of diffusivity and climb over time scales and temperatures relevant to power-law creep. By capturing the underlying microscopic physics, the calculated stress exponents for steady-state creep rates agree quantitatively with the experimentally measured range, and qualitatively with the stress dependence of creep activation energies.

  20. Grain size, stress and creep in polycrystalline solids

    CSIR Research Space (South Africa)

    Nabarro, FRN

    2000-08-01

    Full Text Available ?Herring sources within the grain and the annihilation of dislocation pairs under their mutual attraction. This process occurs and Harper?Dorn creep is possible if inequality (4) is satisfied. If the inequality is not satisfied, dislocations climb into the grain... by glide. If, in addition, inequality (5) is satisfied, disloca- tions will multiply by glide within the cell much more rapidly than they can annihilate by climb. Harper?Dorn creep gives way to power-law creep [9]. If the product L 1/2 s is less...

  1. Understanding effects of microstructural inhomogeneity on creep response – New approaches to improve the creep resistance in magnesium alloys

    Directory of Open Access Journals (Sweden)

    Yuanding Huang

    2014-06-01

    Full Text Available Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries. These stable intermetallic phases were considered to be effective to suppress the deformation by grain boundary sliding, leading to the improvement of creep properties. Based on this point, adding the alloying elements to form the stable intermetallics with high melting point became a popular way to develop the new creep resistant magnesium alloys. The present investigation, however, shows that the creep properties of binary Mg–Sn alloy are still poor even though the addition of Sn possibly results in the precipitation of thermal stable Mg2Sn at grain boundaries. That means other possible mechanisms function to affect the creep response. It is finally found that the poor creep resistance is attributed to the segregation of Sn at dendritic and grain boundaries. Based on this observation, new approaches to improve the creep resistance are suggested for magnesium alloys because most currently magnesium alloys have the commonality with the Mg–Sn alloys.

  2. A Model for Creep and Creep Damage in the γ-Titanium Aluminide Ti-45Al-2Mn-2Nb

    Directory of Open Access Journals (Sweden)

    William Harrison

    2014-03-01

    Full Text Available Gamma titanium aluminides (γ-TiAl display significantly improved high temperature mechanical properties over conventional titanium alloys. Due to their low densities, these alloys are increasingly becoming strong candidates to replace nickel-base superalloys in future gas turbine aeroengine components. To determine the safe operating life of such components, a good understanding of their creep properties is essential. Of particular importance to gas turbine component design is the ability to accurately predict the rate of accumulation of creep strain to ensure that excessive deformation does not occur during the component’s service life and to quantify the effects of creep on fatigue life. The theta (θ projection technique is an illustrative example of a creep curve method which has, in this paper, been utilised to accurately represent the creep behaviour of the γ-TiAl alloy Ti -45Al-2Mn-2Nb. Furthermore, a continuum damage approach based on the θ-projection method has also been used to represent tertiary creep damage and accurately predict creep rupture.

  3. Compressive Creep of Prestressed Concrete Mixtures With and Without Mineral Admixtures

    OpenAIRE

    2001-01-01

    Concrete experiences volume changes throughout its service life. When loaded, concrete experiences an instantaneous recoverable elastic deformation and a slow inelastic deformation called creep. Creep of concrete is composed of two components, basic creep, or deformation under load without moisture loss and drying creep, or deformation under drying conditions only. Deformation of concrete in the absence of applied load is often called shrinkage. The deformation due to creep is attrib...

  4. Long-term creep properties of cementitious materials: Comparing microindentation testing with macroscopic uniaxial compressive testing

    OpenAIRE

    Zhang, Qing; Le Roy, Robert; VANDAMME, Mathieu; ZUBER, Bruno

    2014-01-01

    This study is dedicated to comparing minutes-long microindentation creep experiments on cement paste with years-long macroscopic creep experiments on concrete and months-long macroscopic creep experiments on cement paste. For all experiments, after a transient period the creep function was well captured by a logarithmic function of time, the amplitude of which is governed by a so-called creep modulus. The non-logarithmic transient periods lasted for days at the macroscopic scale, but only for...

  5. Investigação de inclusões não metálicas em fios elétricos de alumínio

    Directory of Open Access Journals (Sweden)

    Marcolino Fernandes Neto

    2002-04-01

    Full Text Available Atualmente, um dos grandes desafios enfrentados pelas empresas nacionais fabricantes de condutores elétricos, de alumínio, tem sido a ocorrência de inclusões não metálicas. Tais inclusões causam a ruptura dos fios ao longo dos processos de laminação, trefilação e encordoamento. Assim, a presença de inclusões não metálicas nesses materiais tem impactos significativos na capacidade de produzir fios elétricos com pequenos diâmetros, bem como no atendimento dos rigorosos requisitos de resistência à tração e à fadiga estabelecidos para esses materiais. Nesse sentido, o presente trabalho analisou as inclusões não metálicas em fios elétricos de alumínio, que causaram a ruptura dos mesmos na etapa do processo de trefilação, através do método metalográfico convencional com auxílio do MEV/EDS, na busca de identificar a origem das inclusões. Também foi desenvolvido, nesse trabalho, um método de separação de inclusões não metálicas, presentes nos fios elétricos de alumínio, através da dissolução da matriz de alumínio em solução de ácido clorídrico. A análise das inclusões isoladas da matriz de alumínio permitiu uma investigação mais ampla quanto ao tamanho, à forma e à quantidade de tais inclusões. Os resultados mostraram que as inclusões responsáveis pelo rompimento dos fios são do tipo alumina e que as mesmas são provenientes do arraste de parte da camada de óxido de alumínio que protege o metal líquido nas calhas revestidas com material refratário.Actually, one of the biggest challenge for the national electrical aluminum conductors industries has been the occurrence of non-metallic inclusions. These inclusions cause the rupture of the wires during the rolling, drawing and bunchering process. Then, the presence of non-metallic inclusions in these materials has significant impact in the capacity of small diameter wire's production, such as to reach rigorous requirements of strength

  6. In-situ Creep Testing Capability Development for Advanced Test Reactor

    Energy Technology Data Exchange (ETDEWEB)

    B. G. Kim; J. L. Rempe; D. L. Knudson; K. G. Condie; B. H. Sencer

    2010-08-01

    Creep is the slow, time-dependent strain that occurs in a material under a constant strees (or load) at high temperature. High temperature is a relative term, dependent on the materials being evaluated. A typical creep curve is shown in Figure 1-1. In a creep test, a constant load is applied to a tensile specimen maintained at a constant temperature. Strain is then measured over a period of time. The slope of the curve, identified in the figure below, is the strain rate of the test during Stage II or the creep rate of the material. Primary creep, Stage I, is a period of decreasing creep rate due to work hardening of the material. Primary creep is a period of primarily transient creep. During this period, deformation takes place and the resistance to creep increases until Stage II, Secondary creep. Stage II creep is a period with a roughly constant creep rate. Stage II is referred to as steady-state creep because a balance is achieved between the work hardening and annealing (thermal softening) processes. Tertiary creep, Stage III, occurs when there is a reduction in cross sectional area due to necking or effective reduction in area due to internal void formation; that is, the creep rate increases due to necking of the specimen and the associated increase in local stress.

  7. Recycling of non-metallic fractions from waste electrical and electronic equipment (WEEE): A review

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ruixue; Xu, Zhenming, E-mail: zmxu@sjtu.edu.cn

    2014-08-15

    Highlights: • NMFs from WEEE were treated by incineration or land filling in the past. • Environmental risks such as heavy metals and BFRs will be the major problems during the NMFs recycling processes. • Methods and technologies of recycling the two types of NMFs from WEEE, plastics, glasses are reviewed. • More environmental impact assessment should be carried out to evaluate the environmental risks of the recycling products. - Abstract: The world’s waste electrical and electronic equipment (WEEE) consumption has increased incredibly in recent decades, which have drawn much attention from the public. However, the major economic driving force for recycling of WEEE is the value of the metallic fractions (MFs). The non-metallic fractions (NMFs), which take up a large proportion of E-wastes, were treated by incineration or landfill in the past. NMFs from WEEE contain heavy metals, brominated flame retardant (BFRs) and other toxic and hazardous substances. Combustion as well as landfill may cause serious environmental problems. Therefore, research on resource reutilization and safe disposal of the NMFs from WEEE has a great significance from the viewpoint of environmental protection. Among the enormous variety of NMFs from WEEE, some of them are quite easy to recycle while others are difficult, such as plastics, glass and NMFs from waste printed circuit boards (WPCBs). In this paper, we mainly focus on the intractable NMFs from WEEE. Methods and technologies of recycling the two types of NMFs from WEEE, plastics, glass are reviewed in this paper. For WEEE plastics, the pyrolysis technology has the lowest energy consumption and the pyrolysis oil could be obtained, but the containing of BFRs makes the pyrolysis recycling process problematic. Supercritical fluids (SCF) and gasification technology have a potentially smaller environmental impact than pyrolysis process, but the energy consumption is higher. With regard to WEEE glass, lead removing is requisite

  8. Creep of metal-type organic compounds. 3: Friction stress models for creep in particle-hardened systems

    Energy Technology Data Exchange (ETDEWEB)

    Davies, G.C.; Jones, D.R.H. [Univ. of Cambridge (United Kingdom). Engineering Dept.

    1996-08-15

    The effect of a dispersed phase of small, hard particles on the creep behavior of two plastic crystals, camphene and succinonitrile, is investigated experimentally. Three models describing the creep deformation of a material containing hard particles are compared to the experimental data. Previous work has considered the particles to result in a constant friction stress which opposes creep deformation. The experimental results for plastic crystals are shown to be equally consistent with a model in which the friction stress is a linear function of the applied stress.

  9. Toward environmentally-benign utilization of nonmetallic fraction of waste printed circuit boards as modifier and precursor.

    Science.gov (United States)

    Hadi, Pejman; Ning, Chao; Ouyang, Weiyi; Xu, Meng; Lin, Carol S K; McKay, Gordon

    2015-01-01

    Electronic waste, including printed circuit boards, is growing at an alarming rate due to the accelerated technological progress and the shorter lifespan of the electronic equipment. In the past decades, due to the lack of proper economic and environmentally-benign recycling technologies, a major fraction of e-waste generated was either destined to landfills or incinerated with the sole intention of its disposal disregarding the toxic nature of this waste. Recently, with the increasing public awareness over their environment and health issues and with the enaction of more stringent regulations, environmentally-benign recycling has been driven to be an alternative option partially replacing the traditional eco-unfriendly disposal methods. One of the most favorable green technologies has been the mechanical separation of the metallic and nonmetallic fraction of the waste printed circuit boards. Although metallic fraction, as the most profitable component, is used to generate the revenue of the separation process, the nonmetallic fraction (NMF) has been left isolated. Herein, the recent developments in the application of NMF have been comprehensively reviewed and an eco-friendly emerging usage of NMF as a value-added material for sustainable remediation has been introduced. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Healing mechanism of nanocrack in nanocrystalline metals during creep process

    Science.gov (United States)

    Meraj, Md.; Pal, Snehanshu

    2017-02-01

    Molecular dynamics (MD) simulation has been performed to demonstrate the fate of cracks present inside ultrafine-grained (grain size 7 nm) nanocrystalline Ni specimen during creep deformation process. It is observed that internal nanocracks are healed within a few pico-seconds of initial part of creep process even if the constant applied load on the specimen is tensile in nature and acting normal to crack surface in the outward direction. This kind of crack-healing phenomenon can be accounted by the facts such as stress-driven grain boundary migration, grain boundary diffusion and amorphization of specimen as per results obtained from this MD simulation. This MD study also reveals that the presence of nanocrack inside ultrafine-grained NC Ni in fact slightly improves creep properties and such enhancement of the creep properties is intensified as the size of internal crack increases.

  11. Creep characterization of gels and nonlinear viscoelastic material model

    Science.gov (United States)

    Ishikawa, Kiyotaka; Fujikawa, Masaki; Makabe, Chobin; Tanaka, Kou

    2016-07-01

    In this paper, we examine gel creep behavior and develop a material model for useful and simple numerical simulation of this behavior. This study has three stages and aims: (1) gel creep behavior is examined; (2) the material model is determined and the material constants are identified; and (3) the versatility of the material model and the constants are evaluated. The creep behavior is found to be independent of the initial stress level in the present experiment. Thus, the viscoelastic model proposed by Simo is selected, and its material constants are identified using the results of creep tests. Moreover, from the results of numerical calculations and experiments, it is found that the chosen material model has good reproducibility, predictive performance and high versatility.

  12. Creep and Shrinkage of High Strength Concretes: an Experimental Analysis

    Directory of Open Access Journals (Sweden)

    Berenice Martins Toralles carbonari

    2002-01-01

    Full Text Available The creep and shrinkage behaviour of high strength silica fume concretes is significantly different from that of conventional concretes. In order to represent the proper time-dependent response of the material in structural analysis and design, these aspects should be adequately quantified. This paper discusses an experimental setup that is able to determine the creep and shrinkage of concrete from the time of placing. It also compares different gages that can be used for measuring the strains. The method is applied to five different concretes in the laboratory under controlled environmental conditions. The phenomena that are quantified can be classified as basic shrinkage, drying shrinkage, basic creep and drying creep. The relative importance of these mechanisms in high strength concrete will also be presented.

  13. Estimation of Rheological Properties of Snow Subjected to Creep

    Directory of Open Access Journals (Sweden)

    Chaman Chandel

    2007-07-01

    Full Text Available Creep is one of the most important phenomenons to determine the settlement of snow. Snow,in natural conditions, exists at temperature quite close to its melting point and deforms very fast.The settlement of snow is the result of creep phenomenon under the action of overburdenpressure as well as due to metamorphic processes going on within the snowpack. In thiscommunication, creep behaviour of snow is simulated with four-parameter viscoelastic fluidmodel. This viscoelastic character is basically controlled or monitored by various rheologicalconstants. Estimation of all the rheological constants in the four-parameter viscoelastic fluidmodel appropriate for the creep properties of snow is done. Total 91 uniaxial unconfined constantstress experiments on sieved snow were conducted at controlled temperature conditions. Theeffect of density and varying temperature on these constants is found to be remarkable.

  14. MULTIAXIAL CREEP-FATIGUE LIFE EVALUATION UNDER PROPORTIONAL LOADING

    Institute of Scientific and Technical Information of China (English)

    Y.Noguchi; M.Miyahara

    2004-01-01

    A new method was proposed for the multiaxial creep-fatigue life evaluation under proportional loadings. Because this method was derived from the strain range partitioning method with a multiaxiality factor, it was possible to consider the influence of both creep-fatigue interaction and multiaxial stress state on fatigue life. In order to predict the combined axial-torsional fatigue life the damage under combined loading was defined as linear summation of the damages under axial loading and torsional loading.Axial-torsional creep-fatigue tests were carried out using tubular specimens of 316LC austenitic stainless steel and the ferritic rotor steel. This rotor steel was developed for the permanent magnet type eddy current retarder in heavy trucks. Experimentally obtained lives of both steels were well corresponded with the lives predicted by the proposed method. It was found that the proposed method was effective in multiaxial fatigue life evaluation under proportional creep-fatigue loadings.

  15. Microstructure evolution of CLAM steel during creep at 923K

    Science.gov (United States)

    Ye, S.; Zhao, F.; Huang, F.; He, J.; Wang, J. L.

    2017-08-01

    The microstructure change of CLAM steel during creep testing process was investigated at the temperature of 923K with different stress. The results show that the fragmentation and polygonization of martensite lath, as well as the degeneration of dislocation structure are the main factors to deteriorate the creep performance. The stability of MX precipitates in CLAM steel during high temperature creep is good, but the amount and size of M23C6 precipitates are increased. The Laves phase was not found in all samples, which may be due to the experimental temperature is close to the dissolution temperature of Laves phase. The higher temperature accelerates the microstructure evolution of CLAM steel, which results in the degradation of creep properties.

  16. Microstructural evolution and creep of Fe-Al-Ta alloys

    Energy Technology Data Exchange (ETDEWEB)

    Prokopcakova, Petra; Svec, Martin [Technical University of Liberec (Czech Republic). Dept. of Material Science; Palm, Martin [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany). Structure and Nano-/Micromechanics of Materials

    2016-05-15

    The microstructural evolution in Fe-Al-Ta alloys containing 23 - 31 at.% Al and 1.5 - 2.2 at.% Ta has been studied in the temperature range 650 - 750 C by annealing for 1, 10, 100 and 1 000 h. The experiments confirm that in this temperature range the precipitation of the stable hexagonal C14 Laves phase is preceded by formation of coherent, metastable L2{sub 1} Heusler phase precipitates within the Fe-Al matrix. However, precipitates of C14 are observed after much shorter annealing times than previously assumed. Creep strength increases substantially with increasing Al content of the alloys because the solid solubility for Ta in the Fe-Al matrix increases with increasing Al content and solid-solution hardening contributes substantially to the observed high creep strength. It may therefore be that the microstructural changes during creep have no noticeable effect on creep strength.

  17. Creep and stress relaxation induced by interface diffusion in metal matrix composites

    Science.gov (United States)

    Li, Yinfeng; Li, Zhonghua

    2013-03-01

    An analytical solution is developed to predict the creep rate induced by interface diffusion in unidirectional fiber-reinforced and particle reinforced composites. The driving force for the interface diffusion is the normal stress acting on the interface, which is obtained from rigorous Eshelby inclusion theory. The closed-form solution is an explicit function of the applied stress, volume fraction and radius of the fiber, as well as the modulus ratio between the fiber and the matrix. It is interesting that the solution is formally similar to that of Coble creep in polycrystalline materials. For the application of the present solution in the realistic composites, the scale effect is taken into account by finite element analysis based on a unit cell. Based on the solution, a closed-form solution is also given as a description of stress relaxation induced by interfacial diffusion under constant strain. In addition, the analytical solution for the interface stress presented in this study gives some insight into the relationship between the interface diffusion and interface slip. This work was supported by the financial support from the Nature Science Foundation of China (No. 10932007), the National Basic Research Program of China (No. 2010CB631003/5), and the Doctoral Program of Higher Education of China (No. 20100073110006).

  18. Modification of Inclusions in Molten Steel by Mg-Ca Transfer from Top Slag: Experimental Confirmation of the `Refractory-Slag-Metal-Inclusion (ReSMI)' Multiphase Reaction Model

    Science.gov (United States)

    Shin, Jae Hong; Park, Joo Hyun

    2017-08-01

    High-temperature experiments and Refractory-Slag-Metal-Inclusion (ReSMI) multiphase reaction simulations were carried out to determine the effect of the ladle slag composition on the formation behavior of non-metallic inclusions in molten steel. Immediately after the slag-metal reaction, magnesium migrated to the molten steel and a MgAl2O4 spinel inclusion was formed due to a reaction between magnesium and alumina inclusions. However, the spinel inclusion changed entirely into a liquid oxide inclusion via the transfer of calcium from slag to metal in the final stage of the reaction. Calcium transfer from slag to metal was more enhanced for lower SiO2 content in the slag. Consequently, the spinel inclusion was modified to form a liquid CaO-Al2O3-MgO-SiO2 inclusion, which is harmless under steelmaking conditions. The modification reaction was more efficient as the SiO2 content in the slag decreases.

  19. Models of Anisotropic Creep in Integral Wing Panel Forming Processes

    Science.gov (United States)

    Oleinikov, A. I.; Oleinikov, A. A.

    2016-08-01

    For a sufficiently wide range of stresses the titanic and aluminummagnesium alloys, as a rule, strained differently in the process of creep under tension and compression along a fixed direction. There are suggested constitutive relations for the description of the steady-state creep of transversely isotropic materials with different tension and compression characteristics. Experimental justification is given to the proposed constitutive equations. Modeling of forming of wing panels of the aircraft are considered.

  20. Experimental Study on the Porosity Creep Properties of Broken Limestone

    Directory of Open Access Journals (Sweden)

    Li Shun-cai

    2016-01-01

    Full Text Available In the underground engineering, the long-term stability of the surrounding rocks (especially the broken rocks containing water and the ground settlement resulted from the seepage-creep coupling above goaf have been the important research subjects concerning the deep mining. For the broken rock, its porosity is an important structural parameter determining its creep properties, and the porosity change rate is more superior to describe the creep characteristics compared with the strain change rate at a certain direction. In this paper, MTS815.02 Rock Mechanics Test System is used to carry out the creep experiments on water-saturated broken limestone, and then the time curves of porosity and of the porosity change rate are obtained. By regression, we have got the relation equation between the porosity change rate with the instant porosity and the stress level during the creep. The study indicates that when the stress retains a constant level, the relation between the porosity change rate and the instant porosity can be fitted with a cubical polynomial. The obtained creep relation equation between the porosity change rate and the instant porosity and the instant stress provides a necessary state equation for studying the coupling between the seepage and the creep of the broken rock. Furthermore, the seepage in the broken rock has been verified to satisfy the Forchheimer’s non-Darcy flow according to our previous studies, and its seepage properties, k, β and ca can all be expressed respectively as the polynomial of the porosity, so, by combining with these three state equations we have obtained the four essential state equations for solving the coupling problems of the seepage and the creep for the broken rocks.

  1. Diametral creep prediction of pressure tube using statistical regression methods

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. [Korea Advanced Inst. of Science and Technology, Daejeon (Korea, Republic of); Lee, J.Y. [Korea Electric Power Research Inst., Daejeon (Korea, Republic of); Na, M.G. [Chosun Univ., Gwangju (Korea, Republic of); Jang, C. [Korea Advanced Inst. of Science and Technology, Daejeon (Korea, Republic of)

    2010-07-01

    Diametral creep prediction of pressure tube in CANDU reactor is an important factor for ROPT calculation. In this study, pressure tube diametral creep prediction models were developed using statistical regression method such as linear mixed model for longitudinal data analysis. Inspection and operating condition data of Wolsong unit 1 and 2 reactors were used. Serial correlation model and random coefficient model were developed for pressure tube diameter prediction. Random coefficient model provided more accurate results than serial correlation model. (author)

  2. Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic-Martensitic Steel

    Science.gov (United States)

    Vanaja, J.; Laha, Kinkar

    2015-10-01

    Tertiary creep deformation behavior of reduced activation ferritic-martensitic (RAFM) steels having different tungsten contents has been assessed. Creep tests were carried out at 823 K (550 °C) over a stress range of 180 to 260 MPa on three heats of the RAFM steel (9Cr-W-0.06Ta-0.22V) with tungsten content of 1, 1.4, and 2.0 wt pct. With creep exposure, the steels exhibited minimum in creep rate followed by progressive increase in creep rate until fracture. The minimum creep rate decreased, rupture life increased, and the onset of tertiary stage of creep deformation delayed with the increase in tungsten content. The tertiary creep behavior has been assessed based on the relationship, , considering minimum creep rate () instead of steady-state creep rate. The increase in tungsten content was found to decrease the rate of acceleration of tertiary parameter ` p.' The relationships between (1) tertiary parameter `p' with minimum creep rate and time spent in tertiary creep deformation and (2) the final creep rate with minimum creep rate revealed that the same first-order reaction rate theory prevailed in the minimum creep rate as well as throughout the tertiary creep deformation behavior of the steel. A master tertiary creep curve of the steels has been developed. Scanning electron microscopic investigation revealed enhanced coarsening resistance of carbides in the steel on creep exposure with increase in tungsten content. The decrease in tertiary parameter ` p' with tungsten content with the consequent decrease in minimum creep rate and increase in rupture life has been attributed to the enhanced microstructural stability of the steel.

  3. Creep behavior for advanced polycrystalline SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States); Kohyama, Akira [Kyoto Univ. (Japan)] [and others

    1997-08-01

    A bend stress relaxation (BSR) test is planned to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Baseline 1 hr and 100 hr BSR thermal creep {open_quotes}m{close_quotes} curves have been obtained for five selected advanced SiC fiber types and for standard Nicalon CG fiber. The transition temperature, that temperature where the S-shaped m-curve has a value 0.5, is a measure of fiber creep resistance. In order of decreasing thermal creep resistance, with the 100 hr BSR transition temperature given in parenthesis, the fibers ranked: Sylramic (1261{degrees}C), Nicalon S (1256{degrees}C), annealed Hi Nicalon (1215{degrees}C), Hi Nicalon (1078{degrees}C), Nicalon CG (1003{degrees}C) and Tyranno E (932{degrees}C). The thermal creep for Sylramic, Nicalon S, Hi Nicalon and Nicalon CG fibers in a 5000 hr irradiation creep BSR test is projected from the temperature dependence of the m-curves determined during 1 and 100 hr BSR control tests.

  4. Denuded Zones, Diffusional Creep, and Grain Boundary Sliding

    Energy Technology Data Exchange (ETDEWEB)

    Wadsworth, J; Ruano, O A; Sherby, O D

    2001-06-27

    The appearance of denuded zones following low stress creep in particle-containing crystalline materials is both a microstructural prediction and observation often cited as irrefutable evidence for the Nabarro-Herring mechanism of diffusional creep. The denuded zones are predicted to be at grain boundaries that are orthogonal to the direction of the applied stress. Furthermore, their dimensions should account for the accumulated plastic flow. In the present paper, the evidence for such denuded zones is critically examined. These zones have been observed during creep of magnesium, aluminum, and nickel-base alloys. The investigation casts serious doubts on the apparently compelling evidence for the link between denuded zones and diffusional creep. Specifically, denuded zones are clearly observed under conditions that are explicitly not diffusional creep. Additionally, the denuded zones are often found in directions that are not orthogonal to the applied stress. Other mechanisms that can account for the observations of denuded zones are discussed. It is proposed that grain boundary sliding accommodated by slip is the rate-controlling process in the stress range where denuded zones have been observed. It is likely that the denuded zones are created by dissolution of precipitates at grain boundaries that are simultaneously sliding and migrating during creep.

  5. Creep in jointed rock masses. State of knowledge

    Energy Technology Data Exchange (ETDEWEB)

    Glamheden, Rune (Golder Associates AB (Sweden)); Hoekmark, Harald (Clay Technology AB, Lund (Sweden))

    2010-06-15

    To describe creep behaviour in hard rock masses in a physically realistic way, elaborate models including various combinations of dash pots, spring elements and sliders would be needed. According to our knowledge, there are at present no numerical tools available that can handle such a creep model. In addition, there are no records over sufficient long time periods of tunnel convergence in crystalline rock that could be used to determine or calibrate values for the model parameters. A possible method to perform bounding estimates of creep movements around openings in a repository may be to use distinct element codes with standard built-in elasto-plastic models. By locally reducing the fracture shear strength near the underground openings a relaxation of fracture shear loads is reached. The accumulated displacements may then represent the maximum possible effects of creep that can take place in a jointed rock mass without reference to the actual time it takes to reach the displacements. Estimates based on results from analyses where all shear stresses are allowed to disappear completely will, however, be over-conservative. To be able to set up and analyse reasonably realistic numerical models with the proposed method, further assumptions regarding the creep movements and the creep region around the opening have to be made. The purpose of this report is to present support for such assumptions as found in the literature.

  6. Creep Behavior and Mechanism for CMCs with Continuous Ceramic Fibers

    Science.gov (United States)

    Chermant, Jean-Louis; Farizy, Gaëlle; Boitier, Guillaume; Darzens, Séverine; Vicens, Jean; Sangleboeuf, Jean-Christophe

    This paper gives an overview on the creep behavior and mechanism of some CMCs, with a SiC ceramic matrix, such as Cf-SiC, SiCf-SiC and SiCf-SiBC. Tensile creep tests were conducted under argon and air in order to have the influence of the environmental conditions on the macroscopical mechanical response. Nevertheless, multi-scale and multi-technique approaches were required to identify and quantify mechanism(s) which is (are) involved in the creep behavior. The initiation and propagation of damages which are occurring under high stress and temperature conditions were investigated at mesoscopic, microscopic and nanoscopic scales using SEM, TEM and HREM, in order to identify the mechanism(s) involved at each scale. Automatic image analysis was used in order to quantify the evolution of some damage morphological parameters. The macroscopical creep behavior has been investigated through a damage mechanics approach which seems to be the most promising route. A good correlation was found between the kinetics of the damage mechanisms and the creep behavior. For such ceramic matrix composites, the governing mechanism is a damage-creep one, with an additional delay effect due to formation of a glass when tests are performed under air.

  7. A Critical Analysis of the Conventionally Employed Creep Lifing Methods

    Directory of Open Access Journals (Sweden)

    Zakaria Abdallah

    2014-04-01

    Full Text Available The deformation of structural alloys presents problems for power plants and aerospace applications due to the demand for elevated temperatures for higher efficiencies and reductions in greenhouse gas emissions. The materials used in such applications experience harsh environments which may lead to deformation and failure of critical components. To avoid such catastrophic failures and also increase efficiency, future designs must utilise novel/improved alloy systems with enhanced temperature capability. In recognising this issue, a detailed understanding of creep is essential for the success of these designs by ensuring components do not experience excessive deformation which may ultimately lead to failure. To achieve this, a variety of parametric methods have been developed to quantify creep and creep fracture in high temperature applications. This study reviews a number of well-known traditionally employed creep lifing methods with some more recent approaches also included. The first section of this paper focuses on predicting the long-term creep rupture properties which is an area of interest for the power generation sector. The second section looks at pre-defined strains and the re-production of full creep curves based on available data which is pertinent to the aerospace industry where components are replaced before failure.

  8. Creep properties of Pb-free solder joints

    Energy Technology Data Exchange (ETDEWEB)

    Song, H.G.; Morris Jr., J.W.; Hua, F.

    2002-04-01

    Describes the creep behavior of three Sn-rich solders that have become candidates for use in Pb-free solder joints: Sn-3.5Ag, Sn-3Ag-0.5Cu and Sn-0.7Cu. The three solders show the same general behavior when tested in thin joints between Cu and Ni/Au metallized pads at temperatures between 60 and 130 C. Their steady-state creep rates are separated into two regimes with different stress exponents(n). The low-stress exponents range from {approx}3-6, while the high-stress exponents are anomalously high (7-12). Strikingly, the high-stress exponent has a strong temperature dependence near room temperature, increasing significantly as the temperature drops from 95 to 60 C. The anomalous creep behavior of the solders appears to be due to the dominant Sn constituent. Joints of pure Sn have stress exponents, n, that change with stress and temperature almost exactly like those of the Sn-rich solder joints. Research on creep in bulk samples of pure Sn suggests that the anomalous temperature dependence of the stress exponent may show a change in the dominant mechanism of creep. Whatever its source, it has the consequence that conventional constitutive relations for steady-state creep must be used with caution in treating Sn-rich solder joints, and qualification tests that are intended to verify performance should be carefully designed.

  9. Long-term creep-rupture failure envelope of epoxy

    Science.gov (United States)

    Melo, José Daniel D.; de Medeiros, Antonio M.

    2014-02-01

    An accelerated testing methodology based on the time-temperature superposition principle has been proposed in the literature for the long-term creep strength of polymer matrices and polymer composites. Also, it has been suggested that a standard master curve may be a feasible assumption to describe the creep behavior in both tension and compression modes. In the present research, strength master curves for an aerospace epoxy (8552) were generated for tension and compression, by shifting strength data measured at various temperatures. The shift function is obtained from superposition of creep-compliance curves obtained at different temperatures. A standard master curve was presented to describe the creep-rupture of the polymer under tension and compression. Moreover, long-term creep-rupture failure envelopes of the polymer were presented based on a two-part failure criterion for homogeneous and isotropic materials. Ultimately, the approach presented allows the prediction of creep-rupture failure envelopes for a time-dependent material based on tensile strengths measured at various temperatures, considering that the ratio between tensile and compressive strengths is known.

  10. ANSYS Creep-Fatigue Assessment tool for EUROFER97 components

    Directory of Open Access Journals (Sweden)

    M. Mahler

    2016-12-01

    Full Text Available The damage caused by creep-fatigue is an important factor for materials at high temperatures. For in-vessel components of fusion reactors the material EUROFER97 is a candidate for structural application where it is subjected to irradiation and cyclic thermo-mechanical loads. To be able to evaluate fusion reactor components reliably, creep-fatigue damage has to be taken into account. In the frame of Engineering Data and Design Integration (EDDI in EUROfusion Technology Work Programme rapid and easy design evaluation is very important to predict the critical regions under typical fusion reactor loading conditions. The presented Creep-Fatigue Assessment (CFA tool is based on the creep-fatigue rules in ASME Boiler Pressure Vessel Code (BPVC Section 3 Division 1 Subsection NH which was adapted to the material EUROFER97 and developed for ANSYS. The CFA tool uses the local stress, maximum elastic strain range and temperature from the elastic analysis of the component performed with ANSYS. For the assessment design fatigue and stress to rupture curves of EUROFER97 as well as isochronous stress vs. strain curves determined by a constitutive model considering irradiation influence are used to deal with creep-fatigue damage. As a result allowable number of cycles based on creep-fatigue damage interaction under given hold times and irradiation rates is obtained. This tool can be coupled with ANSYS MAPDL and ANSYS Workbench utilizing MAPDL script files.

  11. Denuded Zones, Diffusional Creep, and Grain Boundary Sliding

    Energy Technology Data Exchange (ETDEWEB)

    Wadsworth, J; Ruano, O A; Sherby, O D

    2001-06-27

    The appearance of denuded zones following low stress creep in particle-containing crystalline materials is both a microstructural prediction and observation often cited as irrefutable evidence for the Nabarro-Herring mechanism of diffusional creep. The denuded zones are predicted to be at grain boundaries that are orthogonal to the direction of the applied stress. Furthermore, their dimensions should account for the accumulated plastic flow. In the present paper, the evidence for such denuded zones is critically examined. These zones have been observed during creep of magnesium, aluminum, and nickel-base alloys. The investigation casts serious doubts on the apparently compelling evidence for the link between denuded zones and diffusional creep. Specifically, denuded zones are clearly observed under conditions that are explicitly not diffusional creep. Additionally, the denuded zones are often found in directions that are not orthogonal to the applied stress. Other mechanisms that can account for the observations of denuded zones are discussed. It is proposed that grain boundary sliding accommodated by slip is the rate-controlling process in the stress range where denuded zones have been observed. It is likely that the denuded zones are created by dissolution of precipitates at grain boundaries that are simultaneously sliding and migrating during creep.

  12. Cumulative creep fatigue damage in 316 stainless steel

    Science.gov (United States)

    Mcgaw, Michael A.

    1989-01-01

    The cumulative creep-fatigue damage behavior of 316 stainless steel at 1500 F was experimentally established for the two-level loading cases of fatigue followed by fatigue, creep fatigue followed by fatigue, and fatigue followed by creep fatigue. The two-level loadings were conducted such that the lower life (high strain) cycling was applied first for a controlled number of cycles and the higher life (low strain) cycling was conducted as the second level to failure. The target life levels in this study were 100 cycles to failure for both the fatigue and creep-fatigue lowlife loading, 5000 cycles to failure for the higher life fatigue loading and 10,000 cycles to failure for the higher life creep-fatigue loading. The failed specimens are being examined both fractographically and metallographically to ascertain the nature of the damaging mechanisms that produced failure. Models of creep-fatigue damage accumulation are being evaluated and knowledge of the various damaging mechanisms is necessary to ensure that predictive capability is instilled in the final failure model.

  13. Foresighting for Inclusive Development

    DEFF Research Database (Denmark)

    Andersen, Allan Dahl; Andersen, Per Dannemand

    2017-01-01

    We propose that foresight can contribute to inclusive development by making innovation systems more inclusive. Processes of developing future oriented innovation policies are often unsuccessful and rarely inclusive. We conceptualize such processes as foresighting. We focus on how the ex-ante design...... of policymaking processes affects the actual process with a focus on inclusion, and we discuss how it affects policy effectiveness and innovation system transformation. Our argument is that processes of policymaking must be inclusive to affect and transform innovation systems because a set of distributed actors......, rather than ministries and innovation agencies, is the gatekeepers of change. From this perspective, inclusion is a precondition rather than an obstacle for transformation. Based on the notion of innovation system foresight, we develop an analytical framework that we use to study design and processes...

  14. A triaxial creep model for coal containing gas and its stability analysis

    Institute of Scientific and Technical Information of China (English)

    YIN Guang-zhi; WANG Deng-ke; HUANG Gun; ZHANG Dong-ming; WANG Wei-zhong

    2009-01-01

    Triaxial creep tests on CCG specimens were systematically performed using a self-made creep seepage experimental apparatus for determining the creep law of CCG. An improved triaxial creep model of CCG was established on the basis of a Nishihara model and another visco-elasto-plastic model, parameters of which were fitted on test data. Furthermore, the creep model is validated according to the result of triaxial creep experi-ments, and the outcome shows that the proposed triaxial creep model can properly char-acterize the properties of various creep deformation phases of CCG, especially the accel-erating creep phase. At the same time, the instability conditions of CCG were presented based on the discussion of the improved model's stability in terms of stability theories of differential equation solution.

  15. Bott periodicity of inclusions

    CERN Document Server

    Mare, Augustin-Liviu

    2011-01-01

    When looking at Bott's original proof of his periodicity theorem for the stable homotopy groups of the orthogonal and unitary groups, one sees in the background a differential geometric periodicity phenomenon. We show that this geometric phenomenon extends to the standard inclusion of the orthogonal group into the unitary group. This explains the periodicity of the group homomorphisms between stable homotopy groups which are induced by the inclusion map. Standard inclusions between other classical Riemannian symmetric spaces are also discussed.

  16. Measuring Attitudes Toward Inclusion

    Directory of Open Access Journals (Sweden)

    André Kunz

    2010-12-01

    Full Text Available The considerable worldwide demand for an inclusive education system has driven Switzerland to reconsider the approach of segregated schooling for children with Special Educational Needs (SEN. Recently, an agreement was signed among the states with the intention to adopt a more inclusive practice in school. There is evidence suggesting that an inclusive practice established at policy level is not enough, as many times it becomes teacher’s effort to translate the policies in classroom setting. The effectiveness of inclusive practices can be tightly related to the attitude of teachers, parents and students to inclusion of children with SEN in mainstreaming classes. Attitude towards inclusion is an observable construct but it presents difficulties in terms of measurement. For this purpose, in order to evaluate the attitude to inclusion of teachers, parents and students, an American Scale, the 11-items Parent Attitude to Inclusion (Palmer et al., 1998a, 1998b, 2001 and the version for teachers (Stanley, Grimbeek, Bryer, Beamisch, 2003; Bryer, Grimbeek, Beamish, Stanley, 2004, has been slightly modified and translated into German language. The resulting scales have been used to collect data in Switzerland in two regions. Results show that the German version of the scale can be potentially used for reliable measurement of attitudes toward inclusion in German speaking countries.

  17. A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions

    Science.gov (United States)

    Evans, Mark

    2016-12-01

    A new parametric approach, termed the Wilshire equations, offers the realistic potential of being able to accurately lift materials operating at in-service conditions from accelerated test results lasting no more than 5000 hours. The success of this approach can be attributed to a well-defined linear relationship that appears to exist between various creep properties and a log transformation of the normalized stress. However, these linear trends are subject to discontinuities, the number of which appears to differ from material to material. These discontinuities have until now been (1) treated as abrupt in nature and (2) identified by eye from an inspection of simple graphical plots of the data. This article puts forward a statistical test for determining the correct number of discontinuities present within a creep data set and a method for allowing these discontinuities to occur more gradually, so that the methodology is more in line with the accepted view as to how creep mechanisms evolve with changing test conditions. These two developments are fully illustrated using creep data sets on two steel alloys. When these new procedures are applied to these steel alloys, not only do they produce more accurate and realistic looking long-term predictions of the minimum creep rate, but they also lead to different conclusions about the mechanisms determining the rates of creep from those originally put forward by Wilshire.

  18. Mechanical Behavior of Low Porosity Carbonate Rock: From Brittle Creep to Ductile Creep.

    Science.gov (United States)

    Nicolas, A.; Fortin, J.; Gueguen, Y.

    2014-12-01

    Mechanical compaction and associated porosity reduction play an important role in the diagenesis of porous rocks. They may also affect reservoir rocks during hydrocarbon production, as the pore pressure field is modified. This inelastic compaction can lead to subsidence, cause casing failure, trigger earthquake, or change the fluid transport properties. In addition, inelastic deformation can be time - dependent. In particular, brittle creep phenomena have been deeply investigated since the 90s, especially in sandstones. However knowledge of carbonates behavior is still insufficient. In this study, we focus on the mechanical behavior of a 14.7% porosity white Tavel (France) carbonate rock (>98% calcite). The samples were deformed in a triaxial cell at effective confining pressures ranging from 0 MPa to 85 MPa at room temperature and 70°C. Experiments were carried under dry and water saturated conditions in order to explore the role played by the pore fluids. Two types of experiments have been carried out: (1) a first series in order to investigate the rupture envelopes, and (2) a second series with creep experiments. During the experiments, elastic wave velocities (P and S) were measured to infer crack density evolution. Permeability was also measured during creep experiments. Our results show two different mechanical behaviors: (1) brittle behavior is observed at low confining pressures, whereas (2) ductile behavior is observed at higher confining pressures. During creep experiments, these two behaviors have a different signature in term of elastic wave velocities and permeability changes, due to two different mechanisms: development of micro-cracks at low confining pressures and competition between cracks and microplasticity at high confining pressure. The attached figure is a summary of 20 triaxial experiments performed on Tavel limestone under different conditions. Stress states C',C* and C*' and brittle strength are shown in the P-Q space: (a) 20°C and dry

  19. Comprehensive Creep and Thermophysical Performance of Refractory Materials

    Energy Technology Data Exchange (ETDEWEB)

    Ferber, M.K.; Wereszczak, A.; Hemrick, J.A.

    2006-06-29

    Furnace designers and refractory engineers recognize that optimized furnace superstructure design and refractory selection are needed as glass production furnaces are continually striving toward greater output and efficiencies. Harsher operating conditions test refractories to the limit, while changing production technology (such as the conversion to oxy-fuel from traditional air-fuel firing) can alter the way the materials perform [1-3]. Refractories for both oxy- and air-fuel fired furnace superstructures (see Fig. 1) are subjected to high temperatures that may cause them to creep excessively or subside during service if the refractory material is not creep resistant, or if it is subjected to high stress, or both. Furnace designers can ensure that superstructure structural integrity is maintained if the creep behavior of the refractory material is well understood and well represented by appropriate engineering creep models. Several issues limit the abilities of furnace designers to (1) choose the optimum refractory for their applications, (2) optimize the engineering design, or (3) predict the service mechanical integrity of their furnace superstructures. Published engineering creep data are essentially nonexistent for almost all commercially available refractories used for glass furnace superstructures. The limited data that do exist are supplied by the various refractory suppliers. Unfortunately, the suppliers generally have different ways of conducting their mechanical testing, and they interpret and report their data differently. This inconsistency makes it hard for furnace designers to draw fair comparisons between competing grades of candidate refractories. Furthermore, the refractory suppliers' data are often not available in a form that can be readily used for furnace design or for the prediction and design of long-term structural integrity of furnace superstructures. As a consequence, the U.S. Department of Energy (DOE) Industrial Technology Program

  20. Small punch creep test in a 316 austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    Saucedo-Muñoz, Maribel L.

    2015-03-01

    Full Text Available The small punch creep test was applied to evaluate the creep behavior of a 316 type austenitic stainless steel at temperatures of 650, 675 and 700 °C. The small punch test was carried out using a creep tester with a specimen size of 10×10×0.3 mm at 650, 675 and 700 °C using loads from 199 to 512 N. The small punch creep curves show the three stages found in the creep curves of the conventional uniaxial test. The conventional creep relationships which involve parameters such as creep rate, stress, time to rupture and temperature were followed with the corresponding parameters of small punch creep test and they permitted to explain the creep behavior in this steel. The mechanism and activation energy of the deformation process were the grain boundary sliding and diffusion, respectively, during creep which caused the intergranular fracture in the tested specimens.El ensayo de termofluencia por indentación se utilizó para evaluar el comportamiento a la termofluencia en un acero inoxidable austenítico 316. Este ensayo se realizó en una máquina de indentación con muestras de 10×10×0,3 mm a temperaturas de 650, 675 y 700 °C con cargas de 199 a 512 N. Las curvas de termofluencia del ensayo mostraron las tres etapas características observadas en el ensayo convencional de tensión. Asimismo, las principales relaciones de termofluencia entre parámetros como velocidad de termofluencia, esfuerzo, tiempo de ruptura y temperatura se observaron en los parámetros correspondientes al ensayo de indentación, lo que permitió caracterizar el comportamiento de termofluencia en este acero. El mecanismo y la energía de activación del proceso de deformación en la termofluencia corresponden al deslizamiento de los límites de grano y la difusión a través de los mismos, respectivamente, lo cual causó la fractura intergranular en las muestras ensayadas.

  1. Energy Consumption and Carbon Dioxide Emissions of China’s Non-Metallic Mineral Products Industry: Present State, Prospects and Policy Analysis

    Directory of Open Access Journals (Sweden)

    Hui Hu

    2014-11-01

    Full Text Available China is the largest non-metallic mineral producer in the world and one of the key consumers of four major non-metallic mineral products, including cement, refractories, plate glass and ceramics. The non-metallic mineral products industry’s rapid growth has brought about a large demand for energy. The present study provides an overview of China’s non-metallic mineral products industry in terms of production, energy consumption and carbon dioxide emissions. In this industry, the energy efficiency is relatively low and the level of carbon dioxide emission is much higher than developed countries’ average. This study interprets the effects of some newly issued policies and analyses the influential factors in achieving energy conservation and emission reduction goals. It also discusses the prospects for saving energy and emission reduction in the industry. Retrofitting facilities and using new production technologies is imperative. Additionally, implementing market-based policies, promoting industrial transformation and effective international cooperation would help decrease carbon dioxide emissions and energy consumption.

  2. AGC 2 Irradiation Creep Strain Data Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Windes, William E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rohrbaugh, David T. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Swank, W. David [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-08-01

    The Advanced Reactor Technologies Graphite Research and Development Program is conducting an extensive graphite irradiation experiment to provide data for licensing of a high temperature reactor (HTR) design. In past applications, graphite has been used effectively as a structural and moderator material in both research and commercial high temperature gas cooled reactor designs. Nuclear graphite H-451, used previously in the United States for nuclear reactor graphite components, is no longer available. New nuclear graphite grades have been developed and are considered suitable candidates for new HTR reactor designs. To support the design and licensing of HTR core components within a commercial reactor, a complete properties database must be developed for these current grades of graphite. Quantitative data on in service material performance are required for the physical, mechanical, and thermal properties of each graphite grade, with a specific emphasis on data accounting for the life limiting effects of irradiation creep on key physical properties of the HTR candidate graphite grades. Further details on the research and development activities and associated rationale required to qualify nuclear grade graphite for use within the HTR are documented in the graphite technology research and development plan.

  3. Creep and fracture of a model yoghurt

    Science.gov (United States)

    Manneville, Sebastien; Leocmach, Mathieu; Perge, Christophe; Divoux, Thibaut

    2014-11-01

    Biomaterials such as protein or polysaccharide gels are known to behave qualitatively as soft solids and to rupture under an external load. Combining optical and ultrasonic imaging to shear rheology we show that the failure scenario of a model yoghurt, namely a casein gel, is reminiscent of brittle solids: after a primary creep regime characterized by a macroscopically homogeneous deformation and a power-law behavior which exponent is fully accounted for by linear viscoelasticity, fractures nucleate and grow logarithmically perpendicularly to shear, up to the sudden rupture of the gel. A single equation accounting for those two successive processes nicely captures the full rheological response. The failure time follows a decreasing power-law with the applied shear stress, similar to the Basquin law of fatigue for solids. These results are in excellent agreement with recent fiber-bundle models that include damage accumulation on elastic fibers and exemplify protein gels as model, brittle-like soft solids. Work funded by the European Research Council under Grant Agreement No. 258803.

  4. MULTIDIMENSIONALITY OF INCLUSION

    Directory of Open Access Journals (Sweden)

    T. V. Semenovskikh

    2016-01-01

    Full Text Available The article reveals the phenomenon of "multidime nsionality of inclusion", which is considered by the author  in  two  dimensions:  "vertical"  and  "horizontal". "Vertical" dimensional model includes five fu ndamental systems functioning inclusive society: social, economic, institutional, territorial and symbolic. "Horizontal" multidimensionality of inclusion – the inclusion of a person in group activities, his su bjective feeling. The author gives a classification of socio-cultural markers of inclusion in University of Tyumen, with an emphasis on availability and motivation of quality education, additional educational opportunities,  professional  training  (described  by the course "Tutor in inclusive education". The tutor in the inclusive educational environment – the person  having  the  higher  vocational  education  in  the field of special pedagogy and psychology; experience  of  pedagogical,  practical  activities  with  persons with limited opportunities of health; having practical  ideas  of  those  spheres  of  activity  which have a direct bearing on their training. The tutor in inclusion is the reflexive and reflexing personality understanding and holding a framework of the pr ofessional activity. The tutor, during the work with the resource card of the person is also neutral. "The multidimensionality of inclusion" is a metaphor, the translational motion vector from inclusive education to inclusive society.

  5. Super long-term creep tests of advanced HP and IP rotor steels

    Energy Technology Data Exchange (ETDEWEB)

    Tchizhik, A.A. [The Polzunov Central Boiler and Turbine Institute, Department the Fatigue Life of Materials for Power Plans Equipment, St. Petersburg (Russian Federation)

    1998-12-31

    A creep model has been developed for predicting the long-term creep behavior, in excess of 200,000 h for advanced materials.The new creep theory is based on a continuum microdamage model and is used to calculate the fields of stress and strain and wedge and cavities damage in critical components of steam and gas turbines. The application of this new model increases the reliability and service life of modern turbines. The accuracy of the model to predict long - term creep behavior, creep ductility was verified using the data bank of super long-term creep tests of advanced materials. (orig.) 12 refs.

  6. Rate-controlling processes in creep of subgrain containing aluminum materials

    Energy Technology Data Exchange (ETDEWEB)

    Sherby, Oleg D. [Department Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Ruano, Oscar A. [Department Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas, CSIC, Av. Gregorio de Amo, 8, 28040 Madrid (Spain)]. E-mail: ruano@cenim.csic.es

    2005-11-25

    The creep behavior of aluminum alloys containing Bi, Zn, Ge, Cu, Fe, Mn and Ti has been investigated. Aluminum containing solutes that diffused faster than aluminum has faster creep rates and lower activation energies for creep than observed in pure aluminum. Solutes that diffused slower than aluminum have slower creep rates and higher activation energies for creep than observed in pure aluminum. A dislocation climb model in the subgrain boundary that involves solute atom diffusion as the rate-controlling creep process is proposed to explain the results.

  7. Contraction of high strength invar steel during creep test

    Energy Technology Data Exchange (ETDEWEB)

    Myslowicki, T.; Bleck, W. [Dept. of Ferrous Metallurgy, Aachen Univ., Aachen (Germany); Weirich, T.E. [Central Facility for Electron Microscopy, Aachen Univ., Aachen (Germany)

    2003-06-01

    Modern large size Cathode Ray Tubes are equipped with so called ''true flat'' shadowmasks made of Invar steel. The mask is stretched onto a solid frame and both are submitted to a final heat treatment (blackening treatment). Elevated temperatures and pretension make the mask material prone to creep, resulting in disutility of the unit for the application. In order to reduce creep elongation of the mask material to a minimum, Mo added high strength Invar steels have been considered to provide the required specifications. Depending on prior processing this type of Invar steel shows an inexplicable contraction during the creep test. Even though this effect can be perfectly used to fulfil the creep requirements, the mechanisms involved were not understood. Focus of the present work was the examination of the effect of precipitations on the ''negative creep'' behaviour of the investigated Invar steel using carbon extraction replicae, transmission electron microscopy as well as SAED. Information about the chemical composition, morphology, size and number of the precipitations in the different states could be gained. The observations revealed that during the creep test, depending on the prior annealing temperature, the chemical composition of the precipitates changed. The Nb content decreased while simultaneously the Mo content increased. Due to the volume difference caused by Mo in solid solution and in precipitated form respectively, the precipitation of Mo during the creep test is supposed to cause the observed sample contraction. The results can be confirmed by calculating the effect of Mo on the distortion of the FeNi lattice. (orig.)

  8. Proposition of Improved Methodology in Creep Life Extrapolation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo Gon; Park, Jae Young; Jang, Jin Sung [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    To design SFRs for a 60-year operation, it is desirable to have the experimental creep-rupture data for Gr. 91 steel close to 20 y, or at least rupture lives significantly higher than 10{sup 5} h. This requirement arises from the fact that, for the creep design, a factor of 3 times for extrapolation is considered to be appropriate. However, obtaining experimental data close to 20 y would be expensive and also take considerable time. Therefore, reliable creep life extrapolation techniques become necessary for a safe design life of 60 y. In addition, it is appropriate to obtain experimental longterm creep-rupture data in the range 10{sup 5} ∼ 2x10{sup 5} h to improve the reliability of extrapolation. In the present investigation, a new function of a hyperbolic sine ('sinh') form for a master curve in time-temperature parameter (TTP) methods, was proposed to accurately extrapolate the long-term creep rupture stress of Gr. 91 steel. Constant values used for each parametric equation were optimized on the basis of the creep rupture data. Average stress values predicted for up to 60 y were evaluated and compared with those of French Nuclear Design Code, RCC-MRx. The results showed that the master curve of the 'sinh' function was a wider acceptance with good flexibility in the low stress ranges beyond the experimental data. It was clarified clarified that the 'sinh' function was reasonable in creep life extrapolation compared with polynomial forms, which have been used conventionally until now.

  9. Irradiation creep relaxation of void swelling-driven stresses

    Energy Technology Data Exchange (ETDEWEB)

    Hall, M.M., E-mail: hallmm63@comcast.net [MacRay Consulting, 1366 Hillsdale Drive, Monroeville, PA (United States)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Irradiation void swelling can cause distortion of reactor core components. Black-Right-Pointing-Pointer Constrained swelling can drive stresses beyond acceptable levels. Black-Right-Pointing-Pointer Compressive stresses decrease irradiation swelling rates. Black-Right-Pointing-Pointer Irradiation creep relaxes swelling-driven stresses and core restraint forces. Black-Right-Pointing-Pointer Swelling-driven creep stresses are consistent with predictions of a proposed model. - Abstract: Swelling-driven-creep test specimens are used to measure the compressive stresses that develop due to constraint of irradiation void swelling. These specimens use a previously non-irradiated 20% CW Type 316 stainless steel holder to axially restrain two Type 304 stainless steel tubular specimens that were previously irradiated in the US Experimental Breeder Reactor (EBR-II) at 490 Degree-Sign C. One specimen was previously irradiated to fluence levels in the void nucleation regime (9 dpa) and the other in the quasi-steady void growth regime (28 dpa). A lift-off compliance measurement technique was used post-irradiation to determine compressive stresses developed during reirradiation of the two specimen assemblies in Row 7 of EBR-II at temperatures of 547 Degree-Sign C and 504 Degree-Sign C, respectively, to additional damage levels each of about 5 dpa. Results obtained on the higher fluence swelling-driven-creep specimen show that compressive stress due to constraint of swelling retards void swelling to a degree that is consistent with active load uniaxial compression specimens that were irradiated as part of a previously reported multiaxial in-reactor creep experiment. Swelling results obtained on the lower fluence swelling-driven creep specimen show a much larger effect of compressive stress in reducing swelling, demonstrating that the larger effect of stress on swelling is on void nucleation as compared to void growth. Test results are

  10. Inclusive Mathematics Classrooms

    Science.gov (United States)

    Ollerton, Mike

    2009-01-01

    In this article, the author explores the theme of inclusion. Inclusion is one of the themes within the recent Qualifications and Curriculum Authority (QCA) publication: "Engaging mathematics for all learners" and the author had the good fortune to participate in this project. This involved working with five schools which, frivolously, all had a…

  11. Understanding Inclusion in Cyprus

    Science.gov (United States)

    Mamas, Christoforos

    2013-01-01

    This paper provides a framework for understanding inclusion in Cyprus. The evidence base is the result of a six-month qualitative research study in five Cypriot mainstream primary schools. Despite the rhetoric in favour of inclusion, it seems that the Cypriot educational system is still highly segregating in its philosophy and does not fully…

  12. What Counts as Inclusion?

    Science.gov (United States)

    Walton, E.; Nel, N.

    2012-01-01

    In the years since the publication in South Africa of White Paper Six: Special needs education (Department of Education (DoE) 2001) various schools in the state and independent sectors have begun to implement inclusive policies and practices. With reference to the Guidelines for full-service/inclusive schools issued in 2009, and by discussing a…

  13. Understanding Inclusion in Cyprus

    Science.gov (United States)

    Mamas, Christoforos

    2013-01-01

    This paper provides a framework for understanding inclusion in Cyprus. The evidence base is the result of a six-month qualitative research study in five Cypriot mainstream primary schools. Despite the rhetoric in favour of inclusion, it seems that the Cypriot educational system is still highly segregating in its philosophy and does not fully…

  14. Towards Inclusive Schooling.

    Science.gov (United States)

    Ainscow, Mel

    1997-01-01

    Uses classroom vignettes to examine reasons why schools in the United Kingdom are not yet generally successful in including students with disabilities and suggests simple ways that ordinary teachers can implement inclusive practices. These include the importance of teamwork, a school climate which encourages inclusive practices, and teacher…

  15. Index for Inclusion

    Science.gov (United States)

    Smith, Allister

    2005-01-01

    Index for Inclusion is a programme to assist in developing learning and participation in schools. It was written by Tony Booth and Mel Ainscow from the Centre for Studies on Inclusive Education, UK. Central Normal School was pleased to have the opportunity to trial this programme.

  16. Inclusive Services Innovation Configuration

    Science.gov (United States)

    Holdheide, Lynn R.; Reschly, Daniel J.

    2011-01-01

    Teacher preparation to deliver inclusive services to students with disabilities is increasingly important because of changes in law and policy emphasizing student access to, and achievement in, the general education curriculum. This innovation configuration identifies the components of inclusive services that should be incorporated in teacher…

  17. "Opioid creep" is real and may be the cause of "fluid creep".

    Science.gov (United States)

    Sullivan, Stephen R; Friedrich, Jeffrey B; Engrav, Loren H; Round, Kurt A; Heimbach, David M; Heckbert, Susan R; Carrougher, Gretchen J; Lezotte, Dennis C; Wiechman, Shelley A; Honari, Shari; Klein, Matthew B; Gibran, Nicole S

    2004-09-01

    Recent studies have shown that burn patients receive larger volumes of fluids than predicted by the Baxter formula and the reason for this is unclear. One potential reason is that increased analgesics are used which could blunt the response to fluid resuscitation. The purpose of this study was to compare the administration of opioid agonists in patients treated at a single burn center in the 1970s and in the year 2000. We performed a retrospective chart review comparing two matched cohorts. Group I consisted of 11 patients admitted between 1975 and 1978. Group II consisted of 11 patients admitted in 2000 matched for age, sex and %TBSA. Patients in Group II received a significantly higher mean opioid equivalent than those in Group I (26.5 +/- 12.3 versus 3.9 +/- 2.2 in the first 24h, P < 0.001). In addition, in Group II, a larger variety and combination of opioid agonists were used. This review demonstrates a significant increase from the 1970s to 2000 in the type, dose prescribed and dose delivered of opioid agonists. Along with "fluid creep", we have also increased our use of opioid agonists or "opioid creep". Higher doses of opioid agonists may have hemodynamic consequences, which may contribute to the increased fluid volumes.

  18. Diffusional creep and diffusion-controlled dislocation creep and their relation to denuded zones in Mg-ZrH{sub 2} materials

    Energy Technology Data Exchange (ETDEWEB)

    Ruano, O.A. [C.S.I.C., Madrid (Spain). Centro Nacional de Investigaciones Metalurgicas; Sherby, O.D. [Stanford Univ., CA (United States). Dept. of Materials Science and Engineering; Wadsworth, J. [Lawrence Livermore National Lab., CA (United States); Wolfenstine, J. [Univ. of Texas, San Antonio, TX (United States). Div. of Engineering

    1998-03-13

    Langdon`s contention that creep of Mg-0.5 wt% Zr is well characterized by diffusional creep at 400 C is in error. It is shown that Langdon and Gifkins` single analysis of denuded zones formed during creep at 2 MPa, purporting to occur as a result of diffusional creep, in fact, took place in the power-law dislocation creep range where solute atoms are interacting with moving dislocations. This observation supports the earlier conclusions made for creep and denuded zones observed in the hydrided Mg-Zr alloy at 500 C. Furthermore, it is shown that Pickles` data at stresses below 2 MPa at 400 C are not related to diffusional creep as considered by Langdon. In this region, denuded zones appear in both longitudinal and transverse boundaries indicating that grain boundary sliding, accompanied by grain boundary migration, is the principal deformation process. It is proposed that denuded zones are caused by dissolution of precipitates at moving grain boundaries.

  19. Shear creep parameters of simulative soil for deep-sea sediment

    Institute of Scientific and Technical Information of China (English)

    马雯波; 饶秋华; 李鹏; 郭帅成; 冯康

    2014-01-01

    Based on mineral component and in-situ vane shear strength of deep-sea sediment, four kinds of simulative soils were prepared by mixing different bentonites with water in order to find the best simulative soil for the deep-sea sediment collected from the Pacific C-C area. Shear creep characteristics of the simulative soil were studied by shear creep test and shear creep parameters were determined by Burgers creep model. Research results show that the shear creep curves of the simulative soil can be divided into transient creep, unstable creep and stable creep, where the unstable creep stage is very short due to its high water content. The shear creep parameters increase with compressive stress and change slightly or fluctuate to approach a constant value with shear stress, and thus average creep parameters under the same compressive stress are used as the creep parameters of the simulative soil. Traction of the deep-sea mining machine walking at a constant velocity can be calculated by the shear creep constitutive equation of the deep-sea simulative soil, which provides a theoretical basis for safe operation and optimal design of the deep-sea mining machine.

  20. Time-Dependent Behavior of Diabase and a Nonlinear Creep Model

    Science.gov (United States)

    Yang, Wendong; Zhang, Qiangyong; Li, Shucai; Wang, Shugang

    2014-07-01

    Triaxial creep tests were performed on diabase specimens from the dam foundation of the Dagangshan hydropower station, and the typical characteristics of creep curves were analyzed. Based on the test results under different stress levels, a new nonlinear visco-elasto-plastic creep model with creep threshold and long-term strength was proposed by connecting an instantaneous elastic Hooke body, a visco-elasto-plastic Schiffman body, and a nonlinear visco-plastic body in series mode. By introducing the nonlinear visco-plastic component, this creep model can describe the typical creep behavior, which includes the primary creep stage, the secondary creep stage, and the tertiary creep stage. Three-dimensional creep equations under constant stress conditions were deduced. The yield approach index (YAI) was used as the criterion for the piecewise creep function to resolve the difficulty in determining the creep threshold value and the long-term strength. The expression of the visco-plastic component was derived in detail and the three-dimensional central difference form was given. An example was used to verify the credibility of the model. The creep parameters were identified, and the calculated curves were in good agreement with the experimental curves, indicating that the model is capable of replicating the physical processes.

  1. Effect of Inclusion Size and Distribution on the Corrosion Behavior of Medical-Device Grade Nitinol Tubing

    Science.gov (United States)

    Wohlschlögel, Markus; Steegmüller, Rainer; Schüßler, Andreas

    2014-07-01

    Nonmetallic inclusions in Nitinol, such as carbides (TiC) and intermetallic oxides (Ti4Ni2O x ), are known to be triggers for fatigue failure of Nitinol medical devices. These mechanically brittle inclusions are introduced during the melting process. As a result of hot and cold working in the production of Nitinol tubing inclusions are fractionalized due to the mechanical deformation imposed. While the role of inclusions regarding Nitinol fatigue performance has been studied extensively in the past, their effect on Nitinol corrosion behavior was investigated in only a limited number of studies. The focus of the present work was to understand the effect of inclusion size and distribution on the corrosion behavior of medical-device grade Nitinol tubing made from three different ingot sources during different manufacturing stages: (i) for the initial stage (hollow: round bar with centric hole), (ii) after hot drawing, and (iii) after the final drawing step (final tubing dimensions: outer diameter 0.3 mm, wall thickness 0.1 mm). For one ingot source, two different material qualities were investigated. Potentiodynamic polarization tests were performed for electropolished samples of the above-mentioned stages. Results indicate that inclusion size rather than inclusion quantity affects the susceptibility of electropolished Nitinol to pitting corrosion.

  2. Minerogenic System of Magnesian Nonmetallic Deposits in Early Proterozoic Mg-rich Carbonate Formations in Eastern Liaoning Province

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In the early Proterozoic the Liryu Formation and Dashiqiao Formation of eastern Liaoning province, China, there are distributed Mg-rich carbonate rock formations, in which large to superlarge deposits of boron, magnesite, talc, Xiuyan jade etc. occur. The formation of these magnesian nonmetallic deposits was related to early Proterozoic evaporates; then these deposits underwent reworking of regional metamorphism and hydrothermal metasomatism during the Lüliang orogeny and tectono-magmatism during the Indosinian-Yanshanian. Among other things, the Mg-rich carbonates formations, minerogenetic structures and ore-forming fluids played a controlling role in the formation of the mineral deposits. The refore, it can be concluded that the mineral deposits are products of combined processes of the coupling of ore source field, fluid field, thermal field (energy field) and stress field under certain time-space conditions in the early Proterozoic and the late-stage superimposed reworking of tectono-magmatism.

  3. Estimation of the ionic charge of non-metallic species into an electrical discharge through a web application

    Science.gov (United States)

    Pérez Gutiérrez, B. R.; Vera-Rivera, F. H.; Niño, E. D. V.

    2016-08-01

    Estimate the ionic charge generated in electrical discharges will allow us to know more accurately the concentration of ions implanted on the surfaces of nonmetallic solids. For this reason, in this research a web application was developed to allow us to calculate the ionic charge generated in an electrical discharge from the experimental parameters established in an ion implantation process performed in the JUPITER (Joint Universal Plasma and Ion Technologies Experimental Reactor) reactor. The estimated value of the ionic charge will be determined from data acquired on an oscilloscope, during startup and shutdown of electrical discharge, which will then be analyzed and processed. The study will provide best developments with regard to the application of ion implantation in various industrial sectors.

  4. A comparative study of sliding wear of nonmetallic dental restorative materials with emphasis on micromechanical wear mechanisms.

    Science.gov (United States)

    Dupriez, Nataliya Deyneka; von Koeckritz, Ann-Kristin; Kunzelmann, Karl-Heinz

    2015-05-01

    The purpose of this study is to investigate the in vitro tribological behavior of modern nonmetallic restorative materials. Specimen prepared of IPS e.max Press lithium disilicate glass ceramic, IPS Empress Esthetic leucite-reinforced glass ceramic, Everest ZS Blanks yttria-stabilized zirconia and Lava Ultimate composite were subjected to wear using a wear machine designed to simulate occlusal loads. The wear of the investigated materials and antagonists were evaluated by a three-dimensional surface scanner. The quantitative wear test results were used to compare and rank the materials. Specimens were divided into two groups with steatite and alumina antagonists. For each antagonist material an analysis of variance was applied. As a post hoc test of the significant differences, Tukey's honest significant difference test was used. With steatite antagonist: wear of zirconia materials mechanical properties (hardness and fracture toughness) and with materials microstructure. Wear mechanisms are discussed. © 2014 Wiley Periodicals, Inc.

  5. Detection of Surface and Subsurface Cracks in Metallic and Non-Metallic Materials Using a Complementary Split-Ring Resonator

    Directory of Open Access Journals (Sweden)

    Ali Albishi

    2014-10-01

    Full Text Available Available microwave techniques for crack detection have some challenges, such as design complexity and working at a high frequency. These challenges make the sensing apparatus design complex and relatively very expensive. This paper presents a simple method for surface and subsurface crack detection in metallic and non-metallic materials based on complementary split-ring resonators (CSRRs. A CSRR sensor can be patterned on the ground plane of a microstrip line and fabricated using printed circuit board technology. Compared to available microwave techniques for sub-millimeter crack detection, the methods presented here show distinct advantages, such as high spatial resolution, high sensitivity and design simplicity. The response of the CSRR as a sensor for crack detection is studied and analysed numerically. Experimental validations are also presented.

  6. Extreme creep resistance in a microstructurally stable nanocrystalline alloy

    Science.gov (United States)

    Darling, K. A.; Rajagopalan, M.; Komarasamy, M.; Bhatia, M. A.; Hornbuckle, B. C.; Mishra, R. S.; Solanki, K. N.

    2016-09-01

    Nanocrystalline metals, with a mean grain size of less than 100 nanometres, have greater room-temperature strength than their coarse-grained equivalents, in part owing to a large reduction in grain size. However, this high strength generally comes with substantial losses in other mechanical properties, such as creep resistance, which limits their practical utility; for example, creep rates in nanocrystalline copper are about four orders of magnitude higher than those in typical coarse-grained copper. The degradation of creep resistance in nanocrystalline materials is in part due to an increase in the volume fraction of grain boundaries, which lack long-range crystalline order and lead to processes such as diffusional creep, sliding and rotation. Here we show that nanocrystalline copper-tantalum alloys possess an unprecedented combination of properties: high strength combined with extremely high-temperature creep resistance, while maintaining mechanical and thermal stability. Precursory work on this family of immiscible alloys has previously highlighted their thermo-mechanical stability and strength, which has motivated their study under more extreme conditions, such as creep. We find a steady-state creep rate of less than 10-6 per second—six to eight orders of magnitude lower than most nanocrystalline metals—at various temperatures between 0.5 and 0.64 times the melting temperature of the matrix (1,356 kelvin) under an applied stress ranging from 0.85 per cent to 1.2 per cent of the shear modulus. The unusual combination of properties in our nanocrystalline alloy is achieved via a processing route that creates distinct nanoclusters of atoms that pin grain boundaries within the alloy. This pinning improves the kinetic stability of the grains by increasing the energy barrier for grain-boundary sliding and rotation and by inhibiting grain coarsening, under extremely long-term creep conditions. Our processing approach should enable the development of

  7. Extreme creep resistance in a microstructurally stable nanocrystalline alloy.

    Science.gov (United States)

    Darling, K A; Rajagopalan, M; Komarasamy, M; Bhatia, M A; Hornbuckle, B C; Mishra, R S; Solanki, K N

    2016-09-15

    Nanocrystalline metals, with a mean grain size of less than 100 nanometres, have greater room-temperature strength than their coarse-grained equivalents, in part owing to a large reduction in grain size. However, this high strength generally comes with substantial losses in other mechanical properties, such as creep resistance, which limits their practical utility; for example, creep rates in nanocrystalline copper are about four orders of magnitude higher than those in typical coarse-grained copper. The degradation of creep resistance in nanocrystalline materials is in part due to an increase in the volume fraction of grain boundaries, which lack long-range crystalline order and lead to processes such as diffusional creep, sliding and rotation. Here we show that nanocrystalline copper-tantalum alloys possess an unprecedented combination of properties: high strength combined with extremely high-temperature creep resistance, while maintaining mechanical and thermal stability. Precursory work on this family of immiscible alloys has previously highlighted their thermo-mechanical stability and strength, which has motivated their study under more extreme conditions, such as creep. We find a steady-state creep rate of less than 10(-6) per second-six to eight orders of magnitude lower than most nanocrystalline metals-at various temperatures between 0.5 and 0.64 times the melting temperature of the matrix (1,356 kelvin) under an applied stress ranging from 0.85 per cent to 1.2 per cent of the shear modulus. The unusual combination of properties in our nanocrystalline alloy is achieved via a processing route that creates distinct nanoclusters of atoms that pin grain boundaries within the alloy. This pinning improves the kinetic stability of the grains by increasing the energy barrier for grain-boundary sliding and rotation and by inhibiting grain coarsening, under extremely long-term creep conditions. Our processing approach should enable the development of

  8. The uncertainties calculation of acoustic method for measurement of dissipative properties of heterogeneous non-metallic materials

    Directory of Open Access Journals (Sweden)

    Мaryna O. Golofeyeva

    2015-12-01

    Full Text Available The effective use of heterogeneous non-metallic materials and structures needs measurement of reliable values of dissipation characteristics, as well as common factors of their change during the loading process. Aim: The aim of this study is to prepare the budget for measurement uncertainty of dissipative properties of composite materials. Materials and Methods: The method used to study the vibrational energy dissipation characteristics based on coupling of vibrations damping decrement and acoustic velocity in a non-metallic heterogeneous material is reviewed. The proposed method allows finding the dependence of damping on vibrations amplitude and frequency of strain-stress state of material. Results: Research of the accuracy of measurement method during the definition of decrement attenuation of fluctuations in synthegran was performed. The international approach for evaluation of measurements quality is used. It includes the common practice international rules for uncertainty expression and their summation. These rules are used as internationally acknowledged confidence measure to the measurement results, which includes testing. The uncertainties budgeting of acoustic method for measurement of dissipative properties of materials were compiled. Conclusions: It was defined that there are two groups of reasons resulting in errors during measurement of materials dissipative properties. The first group of errors contains of parameters changing of calibrated bump in tolerance limits, displacement of sensor in repeated placement to measurement point, layer thickness variation of contact agent because of irregular hold-down of resolvers to control surface, inaccuracy in reading and etc. The second group of errors is linked with density and Poisson’s ratio measurement errors, distance between sensors, time difference between signals of vibroacoustic sensors.

  9. Driven Interfaces: From Flow to Creep Through Model Reduction

    Science.gov (United States)

    Agoritsas, Elisabeth; García-García, Reinaldo; Lecomte, Vivien; Truskinovsky, Lev; Vandembroucq, Damien

    2016-09-01

    The response of spatially extended systems to a force leading their steady state out of equilibrium is strongly affected by the presence of disorder. We focus on the mean velocity induced by a constant force applied on one-dimensional interfaces. In the absence of disorder, the velocity is linear in the force. In the presence of disorder, it is widely admitted, as well as experimentally and numerically verified, that the velocity presents a stretched exponential dependence in the force (the so-called `creep law'), which is out of reach of linear response, or more generically of direct perturbative expansions at small force. In dimension one, there is no exact analytical derivation of such a law, even from a theoretical physical point of view. We propose an effective model with two degrees of freedom, constructed from the full spatially extended model, that captures many aspects of the creep phenomenology. It provides a justification of the creep law form of the velocity-force characteristics, in a quasistatic approximation. It allows, moreover, to capture the non-trivial effects of short-range correlations in the disorder, which govern the low-temperature asymptotics. It enables us to establish a phase diagram where the creep law manifests itself in the vicinity of the origin in the force-system-size-temperature coordinates. Conjointly, we characterise the crossover between the creep regime and a linear-response regime that arises due to finite system size.

  10. Creep Behavior of Poly(lactic acid) Based Biocomposites

    Science.gov (United States)

    Morreale, Marco; Mistretta, Maria Chiara; Fiore, Vincenzo

    2017-01-01

    Polymer composites containing natural fibers are receiving growing attention as possible alternatives for composites containing synthetic fibers. The use of biodegradable matrices obtained from renewable sources in replacement for synthetic ones is also increasing. However, only limited information is available about the creep behavior of the obtained composites. In this work, the tensile creep behavior of PLA based composites, containing flax and jute twill weave woven fabrics, produced through compression molding, was investigated. Tensile creep tests were performed at different temperatures (i.e., 40 and 60 °C). The results showed that the creep behavior of the composites is strongly influenced by the temperature and the woven fabrics used. As preliminary characterization, quasi-static tensile tests and dynamic mechanical tests were carried out on the composites. Furthermore, fabrics (both flax and jute) were tested as received by means of quasi-static tests and creep tests to evaluate the influence of fabrics mechanical behavior on the mechanical response of the resulting composites. The morphological analysis of the fracture surface of the tensile samples showed the better fiber-matrix adhesion between PLA and jute fabric. PMID:28772755

  11. Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates

    Science.gov (United States)

    Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H.; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N.; Huang, Shenyan; Teng, Zhenke; Liu, Chain T.; Asta, Mark D.; Gao, Yanfei; Dunand, David C.; Ghosh, Gautam; Chen, Mingwei; Fine, Morris E.; Liaw, Peter K.

    2015-01-01

    There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. The present research will broaden the applications of ferritic alloys to higher temperatures. PMID:26548303

  12. STUDY THE CREEP OF TUBULAR SHAPED FIBER REINFORCED COMPOSITES

    Directory of Open Access Journals (Sweden)

    Najat J. Saleh

    2013-05-01

    Full Text Available Inpresent work tubular –shaped fiber reinforced composites were manufactured byusing two types of resins ( Epoxy and unsaturated polyester and separatelyreinforced with glass, carbon and kevlar-49 fibers (filament and woven roving,hybrid reinforcement composites of these fibers were also prepared. The fiberswere wet wound on a mandrel using a purposely designed winding machine,developed by modifying an ordinary lathe, in winding angle of 55° for filament. A creep test was made of either the fulltube or specimens taken from it. Creep was found to increase upon reinforcementin accordance to the rule of mixture and mainly decided by the type of singleor hybridized fibers. The creep behavior, showed that the observed strain tendsto appear much faster at higher temperature as compared with that exhibited atroom temperate. The creep rate also found to be depending on fiber type, matrixtype, and the fiber /matrix bonding. The creep energy calculated fromexperimental observations was found to exhibit highest value for hybridizedreinforcement.

  13. Creep Behaviour of Fly Ash-Based Geopolymer Concrete

    Directory of Open Access Journals (Sweden)

    Wallah S.E.

    2010-01-01

    Full Text Available Fly ash-based geopolymer concrete is manufactured using fly ash as its source material and does not use Portland cement at all. Beside fly ash, alkaline solution is also utilized to make geopolymer paste which binds the aggregates to form geopolymer concrete. This paper presents the study of creep behaviour of fly ash-based geopolymer concrete. Four series of specimens with various compressive strengths were prepared to study its creep behaviour for the duration of test up to one year. The test method followed the procedures applied for Ordinary Portland Cement (OPC concrete. Test results show that fly ash-based geopolymer concrete undergoes low creep which is generally less than that of OPC concrete. After one year of loading, the results for specific creep of fly ash-based geopolymer concrete in this study ranges from 15 to 29 microstrain for concrete compressive strength 67–40 MPa respectively. From the test results, it is also found out that the creep coefficient of fly ash-based geopolymer concrete is about half of that predicted using Gilbert’s Method for OPC concrete.

  14. Creep Behavior of Poly(lactic acid Based Biocomposites

    Directory of Open Access Journals (Sweden)

    Marco Morreale

    2017-04-01

    Full Text Available Polymer composites containing natural fibers are receiving growing attention as possible alternatives for composites containing synthetic fibers. The use of biodegradable matrices obtained from renewable sources in replacement for synthetic ones is also increasing. However, only limited information is available about the creep behavior of the obtained composites. In this work, the tensile creep behavior of PLA based composites, containing flax and jute twill weave woven fabrics, produced through compression molding, was investigated. Tensile creep tests were performed at different temperatures (i.e., 40 and 60 °C. The results showed that the creep behavior of the composites is strongly influenced by the temperature and the woven fabrics used. As preliminary characterization, quasi-static tensile tests and dynamic mechanical tests were carried out on the composites. Furthermore, fabrics (both flax and jute were tested as received by means of quasi-static tests and creep tests to evaluate the influence of fabrics mechanical behavior on the mechanical response of the resulting composites. The morphological analysis of the fracture surface of the tensile samples showed the better fiber-matrix adhesion between PLA and jute fabric.

  15. Standard test method for creep-fatigue crack growth testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This test method covers the determination of creep-fatigue crack growth properties of nominally homogeneous materials by use of pre-cracked compact type, C(T), test specimens subjected to uniaxial cyclic forces. It concerns fatigue cycling with sufficiently long loading/unloading rates or hold-times, or both, to cause creep deformation at the crack tip and the creep deformation be responsible for enhanced crack growth per loading cycle. It is intended as a guide for creep-fatigue testing performed in support of such activities as materials research and development, mechanical design, process and quality control, product performance, and failure analysis. Therefore, this method requires testing of at least two specimens that yield overlapping crack growth rate data. The cyclic conditions responsible for creep-fatigue deformation and enhanced crack growth vary with material and with temperature for a given material. The effects of environment such as time-dependent oxidation in enhancing the crack growth ra...

  16. Creep Function of a Single Living Cell

    Science.gov (United States)

    Desprat, Nicolas; Richert, Alain; Simeon, Jacqueline; Asnacios, Atef

    2005-01-01

    We used a novel uniaxial stretching rheometer to measure the creep function J(t) of an isolated living cell. We show, for the first time at the scale of the whole cell, that J(t) behaves as a power-law J(t) = Atα. For N = 43 mice myoblasts (C2-7), we find α = 0.24 ± 0.01 and A = (2.4 ± 0.3) 10−3 Pa−1 s−α. Using Laplace Transforms, we compare A and α to the parameters G0 and β of the complex modulus G*(ω) = G0ωβ measured by other authors using magnetic twisting cytometry and atomic force microscopy. Excellent agreement between A and G0 on the one hand, and between α and β on the other hand, indicated that the power-law is an intrinsic feature of cell mechanics and not the signature of a particular technique. Moreover, the agreement between measurements at very different size scales, going from a few tens of nanometers to the scale of the whole cell, suggests that self-similarity could be a central feature of cell mechanical structure. Finally, we show that the power-law behavior could explain previous results first interpreted as instantaneous elasticity. Thus, we think that the living cell must definitely be thought of as a material with a large and continuous distribution of relaxation time constants which cannot be described by models with a finite number of springs and dash-pots. PMID:15596508

  17. Primary and secondary creep in aluminum alloys as a solid state transformation

    Science.gov (United States)

    Fernández, R.; Bruno, G.; González-Doncel, G.

    2016-08-01

    Despite the massive literature and the efforts devoted to understand the creep behavior of aluminum alloys, a full description of this phenomenon on the basis of microstructural parameters and experimental conditions is, at present, still missing. The analysis of creep is typically carried out in terms of the so-called steady or secondary creep regime. The present work offers an alternative view of the creep behavior based on the Orowan dislocation dynamics. Our approach considers primary and secondary creep together as solid state isothermal transformations, similar to recrystallization or precipitation phenomena. In this frame, it is shown that the Johnson-Mehl-Avrami-Kolmogorov equation, typically used to analyze these transformations, can also be employed to explain creep deformation. The description is fully compatible with present (empirical) models of steady state creep. We used creep curves of commercially pure Al and ingot AA6061 alloy at different temperatures and stresses to validate the proposed model.

  18. Experimental Investigation on Creep Deformation Behavior of Medium-strength Marble Rock

    Directory of Open Access Journals (Sweden)

    Li Yong

    2014-01-01

    Full Text Available The creep deformation behavior of rocks has significant effect on the stability of underground structures. This study presents the short-term and creep deformation behavior of medium-strength marble rock using a conventional uniaxial compression testing machine and a servo-controlled rheology testing machine. The uniaxial compressive strength is obtained by the uniaxial compression testing machine. During the creep behavior test, two types of rock specimens (dry and water-saturated are specified to be used to perform the uniaxial creep tests. Two rheological failure modes and the relationship curves between axial/circumferential strain and stress levels of marble specimens are also obtained from the creep test results. Eventually, the creep deformation behaviors are compared with those of typical soft rocks. These creep curves combined with a given creep constitutive model would provide accurate parameters for long-term stability analyses of actual projects.

  19. Use of groundwater flow model in the analysis of a creeping landslide in western Japan

    Institute of Scientific and Technical Information of China (English)

    H.K.Shrestha; R.Yatabe; N.P.Bhandary

    2006-01-01

    @@ To predict the movement of an existing creeping landslide, monitoring and analysis of hydrological parameters are crucial. This paper analyses the hydrological parameters of an existing creeping landslide site in western Japan.

  20. The dependence of irradiation creep in austenitic alloys on displacement rate and helium to dpa ratio

    Energy Technology Data Exchange (ETDEWEB)

    Garner, F.A. [Pacific Northwest National Lab., Richland, WA (United States); Toloczko, M.B. [Washington State Univ., WA (United States); Grossbeck, M.L. [Oak Ridge National Lab., TN (United States)

    1998-03-01

    Before the parametric dependencies of irradiation creep can be confidently determined, analysis of creep data requires that the various creep and non-creep strains be separated, as well as separating the transient, steady-state, and swelling-driven components of creep. When such separation is attained, it appears that the steady-state creep compliance, B{sub o}, is not a function of displacement rate, as has been previously assumed. It also appears that the formation and growth of helium bubbles under high helium generation conditions can lead to a significant enhancement of the irradiation creep coefficient. This is a transient influence that disappears as void swelling begins to dominate the total strain, but this transient can increase the apparent creep compliance by 100--200% at relatively low ({le}20) dpa levels.