Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

Science.gov (United States)

Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

2016-01-01

The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

Precipitation and Hardening in Magnesium Alloys

Science.gov (United States)

Nie, Jian-Feng

2012-11-01

Magnesium alloys have received an increasing interest in the past 12 years for potential applications in the automotive, aircraft, aerospace, and electronic industries. Many of these alloys are strong because of solid-state precipitates that are produced by an age-hardening process. Although some strength improvements of existing magnesium alloys have been made and some novel alloys with improved strength have been developed, the strength level that has been achieved so far is still substantially lower than that obtained in counterpart aluminum alloys. Further improvements in the alloy strength require a better understanding of the structure, morphology, orientation of precipitates, effects of precipitate morphology, and orientation on the strengthening and microstructural factors that are important in controlling the nucleation and growth of these precipitates. In this review, precipitation in most precipitation-hardenable magnesium alloys is reviewed, and its relationship with strengthening is examined. It is demonstrated that the precipitation phenomena in these alloys, especially in the very early stage of the precipitation process, are still far from being well understood, and many fundamental issues remain unsolved even after some extensive and concerted efforts made in the past 12 years. The challenges associated with precipitation hardening and age hardening are identified and discussed, and guidelines are outlined for the rational design and development of higher strength, and ultimately ultrahigh strength, magnesium alloys via precipitation hardening.

High-throughput design of low-activation, high-strength creep-resistant steels for nuclear-reactor applications

Energy Technology Data Exchange (ETDEWEB)

Lu, Qi; Zwaag, Sybrand van der [Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands); Xu, Wei, E-mail: xuwei@ral.neu.edu.cn [State Key Laboratory of Rolling and Automation, Northeastern University, 110819, Shenyang (China); Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands)

2016-02-15

Reduced-activation ferritic/martensitic steels are prime candidate materials for structural applications in nuclear power reactors. However, their creep strength is much lower than that of creep-resistant steel developed for conventional fossil-fired power plants as alloying elements with a high neutron activation cannot be used. To improve the creep strength and to maintain a low activation, a high-throughput computational alloy design model coupling thermodynamics, precipitate-coarsening kinetics and an optimization genetic algorithm, is developed. Twelve relevant alloying elements with either low or high activation are considered simultaneously. The activity levels at 0–10 year after the end of irradiation are taken as optimization parameter. The creep-strength values (after exposure for 10 years at 650 °C) are estimated on the basis of the solid-solution strengthening and the precipitation hardening (taking into account precipitate coarsening). Potential alloy compositions leading to a high austenite fraction or a high percentage of undesirable second phase particles are rejected automatically in the optimization cycle. The newly identified alloys have a much higher precipitation hardening and solid-solution strengthening at the same activity level as existing reduced-activation ferritic/martensitic steels.

Thermomechanical properties of radiation hardened oligoesteracrylates

International Nuclear Information System (INIS)

Lomonosova, N.V.; Chikin, Yu.A.

1984-01-01

Thermomechanical properties of radiation hardened oligoesteracrylates are studied by the methods of isothermal heating and thermal mechanics. Films of dimethacrylate of ethylene glycol, triethylene glycol (TGM-3), tetraethylene glycol, tridecaethylene glycol and TGM-3 mixture with methyl methacrylate hardened by different doses (5-150 kGy) using Co 60 installation with a dose rate of 2x10 -3 kGy/s served as a subject of the research. During oligoesteracrylate hargening a space network is formed, chain sections between lattice points of which are in a stressed state. Maximum of deformation is observed at 210-220 deg C on thermomechanical curves of samples hardened by doses > 5 kGy, which form and intensity is dependent on an absorbed dose. Presence of a high-temperature maximum on diaqrams of isometric heating of spatially cross-linked oligoesteracrylates is discovered. High thermal stability of three-dimensional network of radiation hardened oligoesteracrylates provides satisfactory tensile properties (40% of initial strength) in sample testing an elevated temperatures (200-250 deg C)

Improving Strength-Ductility Balance of High Strength Dual-Phase Steels by Addition of Vanadium

Science.gov (United States)

Gong, Yu; Hua, M.; Uusitalo, J.; DeArdo, A. J.

For galvanized or galvannealed steels to be commercially successful, they must exhibit several attributes: (i) easy and inexpensive processing in the hot mill, cold mill and on the coating line, (ii) high strength with good formability and spot weldability, and (iii) good corrosion resistance, especially after cold forming. For good corrosion resistance, the coating must have sufficient coverage, be of uniform thickness, and most importantly, the coating must survive the cold stamping or forming operation. The purpose of this paper is to present research aiming at improving the steel substrate, such that high strength can be obtained while maintaining good global formability (tensile ductility), local formability (sheared-edge ductility), and good spot weldability. It is well-known that the strength of DP steels is controlled by several factors, including the amount of martensite found in the final microstructure. Recent research has revealed that the amount of austenite formed during intercritical annealing can be strongly influenced by the annealing temperature and the pre-annealing conditions of the hot band (coiling temperature) and cold band (% cold reduction). Current experiments have explored the combination of pre-annealing conditions and four annealing practices to help define the best practice to optimize the strength-formability balance in these higher strength DP steels. The steels used in these experiments contained (i) low carbon content for good spot weldability, (ii) the hardenability additions Mo and Cr for strength, and (iii) V for grain refinement, precipitation hardening and temper resistance. When processed correctly, these steels exhibited UTS levels up to 1000MPa, total elongation to 25%, reduction in area to 45%, and Hole Expansion Ratios to 50%. The results of this program will be presented and discussed.

Gradient twinned 304 stainless steels for high strength and high ductility

Energy Technology Data Exchange (ETDEWEB)

Chen, Aiying [School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai (China); Liu, Jiabin; Wang, Hongtao [Institute of Applied Mechanics, Zhejiang University, Hangzhou (China); Lu, Jian, E-mail: jianlu@cityu.edu.hk [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong (China); Wang, Y. Morris, E-mail: ymwang@llnl.gov [Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA (United States)

2016-06-14

Gradient materials often have attractive mechanical properties that outperform uniform microstructure counterparts. It remains a difficult task to investigate and compare the performance of various gradient microstructures due to the difficulty of fabrication, the wide range of length scales involved, and their respective volume percentage variations. We have investigated four types of gradient microstructures in 304 stainless steels that utilize submicrotwins, nanotwins, nanocrystalline-, ultrafine- and coarse-grains as building blocks. Tensile tests reveal that the gradient microstructure consisting of submicrotwins and nanotwins has a persistent and stable work hardening rate and yields an impressive combination of high strength and high ductility, leading to a toughness that is nearly 50% higher than that of the coarse-grained counterpart. Ex- and in-situ transmission electron microscopy indicates that nanoscale and submicroscale twins help to suppress and limit martensitic phase transformation via the confinement of martensite within the twin lamellar. Twinning and detwinning remain active during tensile deformation and contribute to the work hardening behavior. We discuss the advantageous properties of using submicrotwins as the main load carrier and nanotwins as the strengthening layers over those coarse and nanocrystalline grains. Our work uncovers a new gradient design strategy to help metals and alloys achieve high strength and high ductility.

Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete

Science.gov (United States)

Safiuddin, Md.; Raman, Sudharshan N.; Zain, Muhammad Fauzi Mohd.

2015-01-01

The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete. PMID:28793732

Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete.

Science.gov (United States)

Safiuddin, Md; Raman, Sudharshan N; Zain, Muhammad Fauzi Mohd

2015-12-10

The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete.

Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete

Directory of Open Access Journals (Sweden)

Md. Safiuddin

2015-12-01

Full Text Available The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete.

The microstructural origin of work hardening stages

DEFF Research Database (Denmark)

Hughes, D. A.; Hansen, N.

2018-01-01

The strain evolution of the flow stress and work hardening rate in stages III and IV is explored by utilizing a fully described deformation microstructure. Extensive measurements by transmission electron microscopy reveal a hierarchical subdivision of grains by low angle incidental dislocation...... addition of the classical Taylor and Hall-Petch formulations. Model predictions agree closely with experimental values of flow stress and work hardening rate in stages III and IV. Strong connections between the evolutionary stages of the deformation microstructure and work hardening rates create a new...... (modern) basis for the classic problem of work hardening in metals and alloys. These connections lead the way for the future development of ultra high strength ductile metals produced via plastic deformation.(c) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved....

Improving the casting properties of high-strength aluminium alloys:

OpenAIRE

Ekrt, Ondřej; Šerák, Jan; Vojtěch, Dalibor

2004-01-01

Al-Zn-Mg-Cu alloys are examples of high-strength alloys. After age-hardening they often possess tensile strengths of more than 500 MPa. However, their casting properties are relatively poor as a result of solidification intervals that are too wide. Therefore, they often require an extrusion, rolling, or forging treatment, and the production of small series of special parts can, as a consequence, be very expensive. In this study, an improvement in the castability and a reduction of the hot-tea...

Ultrafine-Grained Precipitation Hardened Copper Alloys by Swaging or Accumulative Roll Bonding

Directory of Open Access Journals (Sweden)

Igor Altenberger

2015-05-01

Full Text Available There is an increasing demand in the industry for conductive high strength copper alloys. Traditionally, alloy systems capable of precipitation hardening have been the first choice for electromechanical connector materials. Recently, ultrafine-grained materials have gained enormous attention in the materials science community as well as in first industrial applications (see, for instance, proceedings of NANO SPD conferences. In this study the potential of precipitation hardened ultra-fine grained copper alloys is outlined and discussed. For this purpose, swaging or accumulative roll-bonding is applied to typical precipitation hardened high-strength copper alloys such as Corson alloys. A detailed description of the microstructure is given by means of EBSD, Electron Channeling Imaging (ECCI methods and consequences for mechanical properties (tensile strength as well as fatigue and electrical conductivity are discussed. Finally the role of precipitates for thermal stability is investigated and promising concepts (e.g. tailoring of stacking fault energy for grain size reduction and alloy systems for the future are proposed and discussed. The relation between electrical conductivity and strength is reported.

Processing of Cu-Cr alloy for combined high strength and high conductivity

Directory of Open Access Journals (Sweden)

A.O Olofinjanaa

2017-11-01

Full Text Available High strength and high conductivity (HSHC are two intrinsic properties difficult to combine in metallic alloy design because; almost all strengthening mechanisms also lead to reduced conductivity. Precipitation hardening by nano-sized precipitates had proven to be the most adequate way to achieve the optimum combination of strength and conductivity in copper based alloys. However, established precipitation strengthened Cu- alloys are limited to very dilute concentration of solutes thereby limiting the volume proportion hardening precipitates. In this work, we report the investigation of the reprocessing of higher Cr concentration Cu- based alloys via rapid solidification. It is found that the rapid solidification in the as-cast ribbon imposed combined solution extension and ultra-refinement of Cr rich phases. X-ray diffraction evidences suggest that the solid solution extension was up to 6wt%Cr. Lattice parameters determined confirmed the many folds extension of solid solution of Cr in Cu.  Thermal aging studies of the cast ribbons indicated that peak aging treatments occurred in about twenty minutes. Peak aged hardness ranged from about 200 to well over 300Hv. The maximum peak aged hardness of 380Hv was obtained for alloy containing 6wt.%Cr but with conductivity of about 50%IACS. The best combined strength/conductivity was obtained for 4wt.%Cr  alloy with hardness of 350HV and conductivity of 80% IACS. The high strengths observed are attributed to the increased volume proportion of semi-coherent Cr rich nano-sized precipitates that evolved from the supersaturated solid solution of Cu-Cr that was achieved from the high cooling rates imposed by the ribbon casting process. The rapid overaging of the high Cr concentration Cu-Cr alloy is still a cause for concern in optimising the process for reaching peak HSHC properties. It is still important to investigate a microstructural design to slow or severely restrict the overaging process. The optimum

Recent trends in steel fibered high-strength concrete

International Nuclear Information System (INIS)

Shah, Abid A.; Ribakov, Y.

2011-01-01

Highlights: → Recent studies on steel fibred high strength concrete (SFHSC) are reviewed. → Different design provisions for SFHSC are compared. → Applications of SFHSC in new and existing structures and elements are discussed. → Using non-destructive techniques for quality control of SFHSC are reviewed. -- Abstract: Steel fibered high-strength concrete (SFHSC) became in the recent decades a very popular material in structural engineering. High strength attracts designers and architects as it allows improving the durability as well as the esthetics of a construction. As a result of increased application of SFHSC, many experimental studies are conducted to investigate its properties and to develop new rules for proper design. One of the trends in SFHSC structures is to provide their ductile behavior that is desired for proper structural response to dynamic loadings. An additional goal is to limit development and propagation of macro-cracks in the body of SFHSC elements. SFHSC is tough and demonstrates high residual strengths after appearance of the first crack. Experimental studies were carried out to select effective fiber contents as well as suitable fiber types, to study most efficient combination of fiber and regular steel bar reinforcement. Proper selection of other materials like silica fume, fly ash and super plasticizer has also high importance because of the influence on the fresh and hardened concrete properties. Combination of normal-strength concrete with SFHSC composite two-layer beams leads to effective and low cost solutions that may be used in new structures as well as well as for retrofitting existing ones. Using modern nondestructive testing techniques like acoustic emission and nonlinear ultrasound allows verification of most design parameters and control of SFHSC properties during casting and after hardening. This paper presents recent experimental results, obtained in the field SFHSC and non-destructive testing. It reviews the

Process design of press hardening with gradient material property influence

International Nuclear Information System (INIS)

Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

2011-01-01

Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

Hardening of ODS ferritic steels under irradiation with high-energy heavy ions

Science.gov (United States)

Ding, Z. N.; Zhang, C. H.; Yang, Y. T.; Song, Y.; Kimura, A.; Jang, J.

2017-09-01

Influence of the nanoscale oxide particles on mechanical properties and irradiation resistance of oxide-dispersion-strengthened (ODS) ferritic steels is of critical importance for the use of the material in fuel cladding or blanket components in advanced nuclear reactors. In the present work, impact of structures of oxide dispersoids on the irradiation hardening of ODS ferritic steels was studied. Specimens of three high-Cr ODS ferritic steels containing oxide dispersoids with different number density and average size were irradiated with high-energy Ni ions at about -50 °C. The energy of the incident Ni ions was varied from 12.73 MeV to 357.86 MeV by using an energy degrader at the terminal so that a plateau of atomic displacement damage (∼0.8 dpa) was produced from the near surface to a depth of 24 μm in the specimens. A nanoindentor (in constant stiffness mode with a diamond Berkovich indenter) and a Vickers micro-hardness tester were used to measure the hardeness of the specimens. The Nix-Gao model taking account of the indentation size effect (ISE) was used to fit the hardness data. It is observed that the soft substrate effect (SSE) can be diminished substantially in the irradiated specimens due to the thick damaged regions produced by the Ni ions. A linear correlation between the nano-hardeness and the micro-hardness was found. It is observed that a higher number density of oxide dispersoids with a smaller average diameter corresponds to an increased resistance to irradiation hardening, which can be ascribed to the increased sink strength of oxides/matrix interfaces to point defects. The rate equation approach and the conventional hardening model were used to analyze the influence of defect clusters on irradiation hardening in ODS ferritic steels. The numerical estimates show that the hardening caused by the interstitial type dislocation loops follows a similar trend with the experiment data.

Bake hardening of nanograin AA7075 aluminum alloy

International Nuclear Information System (INIS)

Dehghani, Kamran

2011-01-01

Highlights: ► The bake hardening behavior of AA7075 was studied and compared with its coarse-grain counterpart. ► Nanograin AA7075 exhibited 88–100% increase in bake hardenability. ► Nanograin AA7075 exhibited 36–38% increase in final yield strength after baking. ► Maximum bake hardenability and final yield stress were about 185 MPa and 719 MPa. - Abstract: In the present work, the bake hardening of nanostructured AA7075 aluminum alloy was compared with that of its coarse-grain counterpart. Surface severe plastic deformation (SSPD) was used to produce nanograin layers on both surfaces of workpieces. The nanostructured layers were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The thickness of nanostructured layer, having the grains of 50–110 nm, was about 75 μm on each side of workpiece. The bake hardenability of nanograin and coarse-grain AA7075 was then compared by pre-straining to 2, 4 and 6% followed by baking at 100 °C and 200 °C for 20 min. Comparing to coarse-grain case, there was about 88–100% increase in bake hardenability and about 36–38% increase in yield strength after the bake hardening of present nanograin AA7075. Such an increase in bake hardenability and strength was achieved when the thickness of two nanograin layers was about only one-tenth of the whole thickness.

Improvement of Strength-Toughness-Hardness Balance in Large Cross-Section 718H Pre-Hardened Mold Steel

Science.gov (United States)

Liu, Hanghang; Fu, Paixian; Liu, Hongwei; Li, Dianzhong

2018-01-01

The strength-toughness combination and hardness uniformity in large cross-section 718H pre-hardened mold steel from a 20 ton ingot were investigated with three different heat treatments for industrial applications. The different microstructures, including tempered martensite, lower bainite, and retained austenite, were obtained at equivalent hardness. The microstructures were characterized by using metallographic observations, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and electron back-scattered diffraction (EBSD). The mechanical properties were compared by tensile, Charpy U-notch impact and hardness uniformity tests at room temperature. The results showed that the test steels after normalizing-quenching-tempering (N-QT) possessed the best strength-toughness combination and hardness uniformity compared with the conventional quenched-tempered (QT) steel. In addition, the test steel after austempering-tempering (A-T) demonstrated the worse hardness uniformity and lower yield strength while possessing relatively higher elongation (17%) compared with the samples after N-QT (14.5%) treatments. The better ductility of A-T steel mainly depended on the amount and morphology of retained austenite and thermal/deformation-induced twined martensite. This work elucidates the mechanisms of microstructure evolution during heat treatments and will highly improve the strength-toughness-hardness trade-off in large cross-section steels. PMID:29642642

Improvement of Strength-Toughness-Hardness Balance in Large Cross-Section 718H Pre-Hardened Mold Steel

Directory of Open Access Journals (Sweden)

Hanghang Liu

2018-04-01

Full Text Available The strength-toughness combination and hardness uniformity in large cross-section 718H pre-hardened mold steel from a 20 ton ingot were investigated with three different heat treatments for industrial applications. The different microstructures, including tempered martensite, lower bainite, and retained austenite, were obtained at equivalent hardness. The microstructures were characterized by using metallographic observations, scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD, and electron back-scattered diffraction (EBSD. The mechanical properties were compared by tensile, Charpy U-notch impact and hardness uniformity tests at room temperature. The results showed that the test steels after normalizing-quenching-tempering (N-QT possessed the best strength-toughness combination and hardness uniformity compared with the conventional quenched-tempered (QT steel. In addition, the test steel after austempering-tempering (A-T demonstrated the worse hardness uniformity and lower yield strength while possessing relatively higher elongation (17% compared with the samples after N-QT (14.5% treatments. The better ductility of A-T steel mainly depended on the amount and morphology of retained austenite and thermal/deformation-induced twined martensite. This work elucidates the mechanisms of microstructure evolution during heat treatments and will highly improve the strength-toughness-hardness trade-off in large cross-section steels.

An Anisotropic Hardening Model for Springback Prediction

Science.gov (United States)

Zeng, Danielle; Xia, Z. Cedric

2005-08-01

As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test.

An Anisotropic Hardening Model for Springback Prediction

International Nuclear Information System (INIS)

Zeng, Danielle; Xia, Z. Cedric

2005-01-01

As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test

Mechanical properties of metastable austenitic steels, strengthened by hydroextruction and structural hardening

International Nuclear Information System (INIS)

Beresnev, B.I.; Georgieva, I.Ya.; Eshchenko, R.N.; Teplov, V.A.

1981-01-01

Different regimes of complex strengthening of steels of Fe-Ni-Mo-C system by phase hardening and plastic deformation by hydroextrusion are investigated. It is stated that the degree of strengthening depends on consequence of strengthening operations. Plastic deformation by hydroextrusion of steels stre--ngthened by phase hardening ensures increase of strength (Δσsub(0.2)=500 MPa) at high plasticity (delta=25%). Maximal values of strength properties can be achieved if hydroextrusion is conducted before and after thansverse α→γ-transformation [ru

Design of high-temperature high-strength Al-Ti-V-Zr alloys

International Nuclear Information System (INIS)

Lee, H.M.

1990-01-01

This paper reports that it seems plausible to develop high-strength Al-base alloys useful up to 698K in view of the behavior of nickel base superalloys which resist degradation of mechanical properties to 75 pct of their absolute melting temperature. For high temperature Al alloys, the dispersed hardening phase must not undergo phase transformation to an undesirable phase during long time exposure at the temperature of interest. An additional factor to be considered is the stability of the hardening phase with respect to Ostwald ripening. This coarsening resistance is necessary so that the required strength level can be maintained after the long-time service at high temperatures. The equilibrium crystal structures of Al 3 Ti, Al 3 V and Al 3 Zr are tetragonal D0 22 , D0 22 and D0 23 , respectively. At the temperatures of interest, around 698K, vanadium and titanium are mutually substitutable in the form of Al 3 (Ti, V). Much of titanium and vanadium can be substituted for zirconium in the D0 23 - type Al 3 Zr compound, creating Al 3 (Ti, Zr) and Al 3 (V, Zr), respectively. In particular, it has been reported that fcc L1 2 -structured Al 3 M dispersoids form in the rapidly solidified Al-V-Zr and Al-Ti-Zr systems and both L1 2 and D0 23 -structured Al 3 M phases showed slow coarsening kinetics

Technology of hardening fills for mined spaces

International Nuclear Information System (INIS)

Simek, P.; Holas, M.; Chyla, A.; Pech, P.

1985-01-01

The technology is described of hardening fills for mined spaces of uranium deposits in North Bohemian chalk. A special equipment was developed for the controlled preparation of a hardening mixture. The composition of the fill is determined by the strength of the filled rock, expecially by the standard strength, i.e., the minimal strength of the filling under uniaxial pressure. The said parameter determines the consumption of binding materials and thereby the total costs of the filling. A description is presented of the filling technology, including rabbit tube transport of the mixture and quality control. (Pu)

EFFECT OF HARDENER ON MECHANICAL PROPERTIES OF CARBON FIBRE REINFORCED PHENOLIC RESIN COMPOSITES

Directory of Open Access Journals (Sweden)

S. SULAIMAN

2008-04-01

Full Text Available In this paper the effect of hardener on mechanical properties of carbon reinforced phenolic resin composites is investigated. Carbon fibre is one of the most useful reinforcement materials in composites, its major use being the manufacture of components in the aerospace, automotive, and leisure industries. In this study, carbon fibres are hot pressed with phenolic resin with various percentages of carbon fibre and hardener contents that range from 5-15%. Composites with 15% hardener content show an increase in flexural strength, tensile strength and hardness. The ultimate tensile strength (UTS, flexural strength and hardness for 15% hardener are 411.9 MPa, 51.7 MPa and 85.4 HRR respectively.

The influence of flame hardening process to aluminum 7075 series on the mechanical strength and micro structure

Science.gov (United States)

Koin, Sudibtia Titio; Triyono, Teguh; Surojo, Eko

2018-02-01

The 7075 series alloys are heat treatable wrought aluminum alloys based on the Al-Zn-Mg(-Cu) system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effect of flame hardening process to aluminum 7075 series on the increasing hardness, tensile strength, and evolution of microstructure. A test specimen had made by machining process and flame heating. Temperature of solution heat treatment is varied on 350 °C, 400 °C, 450 °C and 500 °C. After that process a test specimen would be quenched at nitrate-nitrite liquid during 45 minutes and artificial aging at 120°C until two days. The testing specimen consist of hardness and tensile strength according to ASTM. The result showed that specimen had precipitation on microstructure lead to an increase in aluminum properties. On the temperature 450°C solution heat treatment, the aluminum properties reached the highest value, namely, hardness of 129 HVN and tensile strength 570 MPa.

Processing, Microstructures and Properties of a Dual Phase Precipitation-Hardening PM Stainless Steel

Science.gov (United States)

Schade, Christopher

To improve the mechanical properties of PM stainless steels in comparison with their wrought counterparts, a PM stainless steel alloy was developed which combines a dual-phase microstructure with precipitation-hardening. The use of a mixed microstructure of martensite and ferrite results in an alloy with a combination of the optimum properties of each phase, namely strength and ductility. The use of precipitation hardening via the addition of copper results in additional strength and hardness. A range of compositions was studied in combination with various sintering conditions to determine the optimal thermal processing to achieve the desired microstructure. The microstructure could be varied from predominately ferrite to one containing a high percentage of martensite by additions of copper and a variation of the sintering temperature before rapid cooling. Mechanical properties (transverse rupture strength (TRS), yield strength, tensile strength, ductility and impact toughness) were measured as a function of the v/o ferrite in the microstructure. A dual phase alloy with the optimal combination of properties served as the base for introducing precipitation hardening. Copper was added to the base alloy at various levels and its effect on the microstructure and mechanical properties was quantified. Processing at various sintering temperatures led to a range of microstructures; dilatometry was used utilized to monitor and understand the transformations and the formation of the two phases. The aging process was studied as a function of temperature and time by measuring TRS, yield strength, tensile strength, ductility, impact toughness and apparent hardness. It was determined that optimum aging was achieved at 538°C for 1h. Aging at slightly lower temperatures led to the formation of carbides, which contributed to reduced hardness and tensile strength. As expected, at the peak aging temperature, an increase in yield strength and ultimate tensile strength as well as

High strength and high electrical conductivity Cu–Cr system alloys manufactured by hot rolling–quenching process and thermomechanical treatments

International Nuclear Information System (INIS)

Xia Chengdong; Zhang Wan; Kang Zhanyuan; Jia Yanlin; Wu Yifeng; Zhang Rui; Xu Genying; Wang Mingpu

2012-01-01

Highlights: ► HR–Q and thermomechanical treatments are successfully developed to manufacture Cu–Cr system alloys. ► Ordered fcc structure Cr precipitates are considered to be precursors of equilibrium bcc Cr precipitates. ► The Cr precipitates are responsible for the improvement of properties. ► Additions of Zr, Mg and Si bring about significant improvement in properties of Cu–Cr alloy. ► Good properties are ascribed to grain boundary strengthening, strain hardening and precipitation hardening. - Abstract: Cu–Cr system alloy strips were manufactured by an online hot rolling–quenching (HR–Q) process and subsequent thermomechanical treatments. The microstructure and properties of the alloys were investigated by observations of optical microscopy and transmission electron microscopy, and measurements of microhardness and electrical conductivity. The results show that the HR–Q process and thermomechanical treatments are successfully developed to manufacture Cu–Cr system alloy strips with good combinations of strength, conductivity and softening resistance. Ordered fcc structure Cr precipitates, which are decomposed from the thermomechanical treated alloys, are considered to be precursors to the formation of equilibrium bcc Cr precipitates and responsible for the improvement of properties during near peak aging. Small additions of Zr, Mg and Si effectively improve the hardness and softening resistance of Cu–Cr alloy, and slightly reduce the electrical conductivity. The achievement of high strength and high electrical conductivity in the alloys is ascribed to the interactions of grain boundary strengthening, strain hardening and precipitation hardening.

Effect of Hybrid Fibers on the Mechanical Properties of High Strength Concrete

Directory of Open Access Journals (Sweden)

Hamid H. Hussein, Saeed K. Rejeb Hayder T. Abd

2014-04-01

Full Text Available In this study, high strength concrete of 75 MPa compressive strength was investigated. The experimental program was designed to study the effect of fibers and hybrid fibers (steel and polypropylene fibers on the fresh (workability and wet density and hardened properties (compressive strength, splitting strength, flexural strength and dry density of high strength concrete. Results show that decreases in slump flow of all concrete mixtures containing steel, polypropylene and hybrid fibers compared with control mix (0% fiber. Hybrid high strength concrete with steel and polypropylene fibers showed superior compressive, splitting, flexural strengths over the others concrete without or with single fibers content. The test results indicate that the maximum increase in compressive and flexural strengths are obtains with the hybridization ratio (70%steel + 30% polypropylene and were equal to 14.54% and 23.34% respectively, compared with the control mix. While, the maximum increase in splitting tensile strength with (100% steel fiber + 0 polypropylene is 21.19%. 

High Strength and Ductility of Additively Manufactured 316L Stainless Steel Explained

Science.gov (United States)

Shamsujjoha, Md.; Agnew, Sean R.; Fitz-Gerald, James M.; Moore, William R.; Newman, Tabitha A.

2018-04-01

Structure-property relationships of an additively manufactured 316L stainless steel were explored. A scanning electron microscope and electron backscattered diffraction (EBSD) analysis revealed a fine cellular-dendritic (0.5 to 2 μm) substructure inside large irregularly shaped grains ( 100 μm). The cellular structure grows along the crystallographic directions. However, texture analysis revealed that the main texture component is inclined by 15 deg from the building direction. X-ray diffraction line profile analysis indicated a high dislocation density of 1 × 1015 m-2 in the as-built material, which correlates well with the observed EBSD microstructure and high-yield strength, via the traditional Taylor hardening equation. Significant variations in strain hardening behavior and ductility were observed for the horizontal (HB) and vertical (VB) built samples. Ductility of HB and VB samples measured 49 and 77 pct, respectively. The initial growth texture and subsequent texture evolution during tensile deformation are held responsible for the observed anisotropy. Notably, EBSD analysis of deformed samples showed deformation twins, which predominately form in the grains with aligned parallel to the loading direction. The VB samples showed higher twinning activity, higher strain hardening rates at high strain, and therefore, higher ductility. Analysis of annealed samples revealed that the observed microstructures and properties are thermally stable, with only a moderate decrease in strength and very similar levels of ductility and anisotropy, compared with the as-built condition.

Computer modelling of age hardening for cast aluminium alloys

International Nuclear Information System (INIS)

Wu, Linda; Ferguson, W George

2009-01-01

Age hardening, or precipitation hardening, is one of the most widely adopted techniques for strengthening of aluminium alloys. Although various age hardening models have been developed for aluminium alloys, from the large volume of literature reviewed, it appears that the bulk of the research has been concentrated on wrought aluminium alloys, only a few of the established precipitation models have been applied to the casting aluminium alloys. In the present work, there are two modelling methods that have been developed and applied to the casting aluminium alloys A356 and A357. One is based on the Shercliff-Ashby methodology to produce a process model, by which we mean a mathematical relationship between process variables (alloy composition, ageing temperature and time) and material properties (yield strength or hardness) through microstructure evolution (precipitate radius, volume fraction). The other method is based on the Kampmann and Wagner Numerical (KWN) model which deals with concomitant nucleation, growth and coarsening and is thus capable of predicting the full evolution of the particle size distribution and then a strength model is used to evaluate the resulting change in hardness or yield strength at room temperature by taking into account contributions from lattice resistance, solid solution hardening and precipitation hardening.

Strength development of high-strength ductile concrete incorporating Metakaolin and PVA fibers.

Science.gov (United States)

Nuruddin, Muhammad Fadhil; Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

2014-01-01

The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers.

Microstructure of high-strength foam concrete

International Nuclear Information System (INIS)

Just, A.; Middendorf, B.

2009-01-01

Foam concretes are divided into two groups: on the one hand the physically foamed concrete is mixed in fast rotating pug mill mixers by using foaming agents. This concrete cures under atmospheric conditions. On the other hand the autoclaved aerated concrete is chemically foamed by adding aluminium powder. Afterwards it is cured in a saturated steam atmosphere. New alternatives for the application of foam concretes arise from the combination of chemical foaming and air curing in manufacturing processes. These foam concretes are new and innovative building materials with interesting properties: low mass density and high strength. Responsible for these properties are the macro-, meso- and microporosity. Macropores are created by adding aluminium powder in different volumes and with different particle size distributions. However, the microstructure of the cement matrix is affected by meso- and micropores. In addition, the matrix of the hardened cement paste can be optimized by the specific use of chemical additives for concrete. The influence of aluminium powder and chemical additives on the properties of the microstructure of the hardened cement matrices were investigated by using petrographic microscopy as well as scanning electron microscopy.

Prediction of the fatigue curve parameters of high strength steels in terms of the static and microplastic deformations of samples

International Nuclear Information System (INIS)

Shetulov, D.I.; Kryukov, L.T.; Myasnikov, A.M.

2015-01-01

The cycling and static strengths of a wide range of high-strength steels have been experimentally tested. Correlation between the three parameters-microplastic deformation, strain hardening coefficient, and the slope of the curve to the axis of load cycles-has been established [ru

Additively manufactured hierarchical stainless steels with high strength and ductility

Science.gov (United States)

Wang, Y. Morris; Voisin, Thomas; McKeown, Joseph T.; Ye, Jianchao; Calta, Nicholas P.; Li, Zan; Zeng, Zhi; Zhang, Yin; Chen, Wen; Roehling, Tien Tran; Ott, Ryan T.; Santala, Melissa K.; Depond, Philip J.; Matthews, Manyalibo J.; Hamza, Alex V.; Zhu, Ting

2018-01-01

Many traditional approaches for strengthening steels typically come at the expense of useful ductility, a dilemma known as strength-ductility trade-off. New metallurgical processing might offer the possibility of overcoming this. Here we report that austenitic 316L stainless steels additively manufactured via a laser powder-bed-fusion technique exhibit a combination of yield strength and tensile ductility that surpasses that of conventional 316L steels. High strength is attributed to solidification-enabled cellular structures, low-angle grain boundaries, and dislocations formed during manufacturing, while high uniform elongation correlates to a steady and progressive work-hardening mechanism regulated by a hierarchically heterogeneous microstructure, with length scales spanning nearly six orders of magnitude. In addition, solute segregation along cellular walls and low-angle grain boundaries can enhance dislocation pinning and promote twinning. This work demonstrates the potential of additive manufacturing to create alloys with unique microstructures and high performance for structural applications.

Strength Development of High-Strength Ductile Concrete Incorporating Metakaolin and PVA Fibers

Directory of Open Access Journals (Sweden)

Muhammad Fadhil Nuruddin

2014-01-01

Full Text Available The mechanical properties of high-strength ductile concrete (HSDC have been investigated using Metakaolin (MK as the cement replacing material and PVA fibers. Total twenty-seven (27 mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers.

Estimation of radiation hardening in ferritic steels using the cluster dynamics models

Energy Technology Data Exchange (ETDEWEB)

Kwon, Jun Hyun; Kim, Whung Whoe; Hong, Jun Hwa [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

2005-07-01

Evolution of microstructure under irradiation brings about the mechanical property changes of materials, of which the major concern is radiation hardening in this work. Radiation hardening is generally expressed in terms of an increase in yield strength as a function of radiation dose and temperature. Cluster dynamics model for radiation hardening has been developed to describe the evolution of point defects clusters (PDCs) and copperrich precipitates (CRPs). While the mathematical models developed by Stoller focus on the evolution of PDCs in ferritic steels under neutron irradiation, we slightly modify the model by including the CRP growth and estimate the magnitude of hardening induced by PDC and CRP. The model is then used to calculate the changes in yield strength of RPV steels. The calculation results are compared to measured yield strength values, obtained from surveillance testing of PWR vessel steels in France.

Hardened Solar Array High Temperature Adhesive.

Science.gov (United States)

1981-04-01

SHERWOOO. D SASIU.IS F3361S-0-C-201S UNCLASSI ED 1AC-SCG-IOOIIR AFVAL-TR-OL-201? NLm,,hinii EhhhEE11I1 AFWAL-TR-81- 2017 i : HARDENED SOLAR ARRAY D HIGH...Tg and as a consequence forms a film on the container and also precipitates as tacky waxlike particles, rather than the desired flocullated

Microstructural effects on the yield strength and its temperature dependence in a bainitic precipitation hardened Cr-Mo-V steel

International Nuclear Information System (INIS)

Toerroenen, K.; Kotilainen, H.; Nenonen, P.

1980-03-01

The plastic deformation behaviour of a precipitation hardened bainitic Cr-Mo-V steel is analyzed at ambient and low temperatures. The temperature dependent component of the yield strength is composed of the Peierls-Nabarro force and also partly of the strengthening contribution of the lath- and cell boundaries or the solid solution hardening. The temperature dependence below 230 K is in accordance with the models presented by Yanoshevich and Ryvkina as well as Dorn and Rajnak. The temperature independent component can be calculated merely from the dislocation density, which is stabilized by the vanadium-rich carbides. The linear additivity cannot be used for the superposition of the strengthening effects of various strengthening parameters, By using the phenomenological approach starting from the dislocation movement mechanisms upon yielding the laws for the superposition are discussed. (author)

Hydrogen embrittlement susceptibility of laser-hardened 4140 steel

Energy Technology Data Exchange (ETDEWEB)

Tsay, L.W.; Lin, Z.W. [Nat. Taiwan Ocean Univ., Keelung (Taiwan). Inst. of Mater. Eng.; Shiue, R.K. [Institute of Materials Sciences and Engineering, National Dong Hwa University, Hualien, Taiwan (Taiwan); Chen, C. [Institute of Materials Sciences and Engineering, National Taiwan University, Taipei, Taiwan (Taiwan)

2000-10-15

Slow strain rate tensile (SSRT) tests were performed to investigate the susceptibility to hydrogen embrittlement of laser-hardened AISI 4140 specimens in air, gaseous hydrogen and saturated H{sub 2}S solution. Experimental results indicated that round bar specimens with two parallel hardened bands on opposite sides along the loading axis (i.e. the PH specimens), exhibited a huge reduction in tensile ductility for all test environments. While circular-hardened (CH) specimens with 1 mm hardened depth and 6 mm wide within the gauge length were resistant to gaseous hydrogen embrittlement. However, fully hardened CH specimens became susceptible to hydrogen embrittlement for testing in air at a lower strain rate. The strength of CH specimens increased with decreasing the depth of hardened zones in a saturated H{sub 2}S solution. The premature failure of hardened zones in a susceptible environment caused the formation of brittle intergranular fracture and the decrease in tensile ductility. (orig.)

The secondary hardening phenomenon in strain-hardened MP35N alloy

International Nuclear Information System (INIS)

Asgari, S.; El-Danaf, E.; Shaji, E.; Kalidindi, S.R.; Doherty, R.D.

1998-01-01

Mechanical testing and microscopy techniques were used to investigate the influence of aging on the structure and strengthening of MP35N alloy. It was confirmed that aging the deformed material at 600 C for 4 h provided additional strengthening, here referred to as secondary hardening, in addition to the primary strain hardening. The secondary hardening phenomenon was shown to be distinctly different from typical age hardening processes in that it only occurred in material deformed beyond a certain cold work level. At moderate strains, aging caused a shift in the entire stress-strain curve of the annealed material to higher stresses while at high strains, it produced shear localization and limited work softening. The secondary hardening increment was also found to be grain size dependent. The magnitude of the secondary hardening appeared to be controlled by the flow stress in the strain hardened material. A model is proposed to explain the observations and is supported by direct experimental evidence. The model is based on formation of h.c.p. nuclei through the Suzuki mechanism, that is segregation of solute atoms to stacking faults, on aging the strain hardened material. The h.c.p. precipitates appear to thicken only in the presence of high dislocation density produced by prior cold work

Laser beam welding of new ultra-high strength and supra-ductile steels

Science.gov (United States)

Dahmen, Martin

2015-03-01

Ultra-high strength and supra-ductile are entering fields of new applications. Those materials are excellent candidates for modern light-weight construction and functional integration. As ultra-high strength steels the stainless martensitic grade 1.4034 and the bainitic steel UNS 53835 are investigated. For the supra-ductile steels stand two high austenitic steels with 18 and 28 % manganese. As there are no processing windows an approach from the metallurgical base on is required. Adjusting the weld microstructure the Q+P and the QT steels require weld heat treatment. The HSD steel is weldable without. Due to their applications the ultra-high strength steels are welded in as-rolled and strengthened condition. Also the reaction of the weld on hot stamping is reflected for the martensitic grades. The supra-ductile steels are welded as solution annealed and work hardened by 50%. The results show the general suitability for laser beam welding.

Effective longitudinal strength of high temperature metal-matrix composites

International Nuclear Information System (INIS)

Craddock, J.N.; Savvides, I.

1991-01-01

Several models for predicting the longitudinal strength of fiber composites are presented, ranging from a simple netting analysis to a model incorporating curvilinear strain hardening for all the components. Results from these models are presented for tungsten fiber reinforced superalloys, FeCrAlY and MARM200. It is shown that a simple elastic limit micromechanical model does not always adequately describe the useful strength of the composites. The methods proposed here are shown to be more appropriate for predicting the effective composite strength. 2 refs

Strain rate dependent tensile behavior of advanced high strength steels: Experiment and constitutive modeling

International Nuclear Information System (INIS)

Kim, Ji-Hoon; Kim, Daeyong; Han, Heung Nam; Barlat, F.; Lee, Myoung-Gyu

2013-01-01

High strain rate tensile tests were conducted for three advanced high strength steels: DP780, DP980 and TRIP780. A high strain rate tensile test machine was used for applying the strain rate ranging from 0.1/s to 500/s. Details of the measured stress–strain responses were comparatively analyzed for the DP780 and TRIP780 steels which show similar microstructural feature and ultimate tensile strength, but different strengthening mechanisms. The experimental observations included: usual strain rate dependent plastic flow stress behavior in terms of the yield stress (YS), the ultimate tensile strength (UTS), the uniform elongation (UE) and the total elongation (TE) which were observed for the three materials. But, higher strain hardening rate at early plastic strain under quasi-static condition than that of some increased strain rates was featured for TRIP780 steel, which might result from more active transformation during deformation with lower velocity. The uniform elongation that explains the onset of instability and the total elongation were larger in case of TRIP steel than the DP steel for the whole strain rate range, but interestingly the fracture strain measured by the reduction of area (RA) method showed that the TRIP steel has lower values than DP steel. The fractographs using scanning electron microscopy (SEM) at the fractured surfaces were analyzed to relate measured fracture strain and the microstructural difference of the two materials during the process of fracture under various strain rates. Finally, constitutive modeling for the plastic flow stresses under various strain rates was provided in this study. The proposed constitutive law could represent both Hollomon-like and Voce-like hardening laws and the ratio between the two hardening types was efficiently controlled as a function of strain rate. The new strength model was validated successfully under various strain rates for several grades of steels such as mild steels, DP780, TRIP780, DP980 steels.

Correlation of yield strength with irradiation-induced microstructure in AISI 316 stainless steel

International Nuclear Information System (INIS)

Simons, R.L.; Hulbert, L.A.

1985-10-01

Improvements in the correlation of radiation-induced change in yield strength in AISI 316 stainless steel with microstructure were made by re-examining the role of short-range obstacles. Effects due to the size of the obstacles relative to their spacing and shape of the obstacles were applied. The concept of shearing the precipitates instead of bowing around them was used to explain the effects of precipitate hardening. It is concluded that large changes in yield strength may be produced in high swelling materials. Voids will dominate the hardening at high dpa. The increase in hardening will depend on the diameter of the voids even though the swelling in the material is the same. Precipitate hardening at high fluence (>15 dpa) make a significant contribution for irradiation temperatures above 500 0 C

Microalloying in case hardening steels - a challenge for the lean production of gears

Energy Technology Data Exchange (ETDEWEB)

Trute, S.; Bleck, W. [RWTH Aachen (Germany). Dept. of Ferrous Metallurgy; Hippenstiel, F. [Edelstahlwerke Buderus AG, Wetzlar (Germany); Klinkenberg, C. [Niobium Products Company GmbH, Duesseldorf (Germany)

2005-07-01

Case hardening steels cover a dominant fraction of engineering steel production. Particularly with recent developments in automotive power train elements, where good hardenability, high tensile strength, high fatigue strength and high impact resistance are required. With a share of up to 40% the material and the heat treatment process take a main part of the overall manufacturing costs. Production costs can be reduced by shortening the overall process time from the melting to the finishing. New developments in carburising technology with an increased carburising temperature offer the possibility of time and cost reduction. Simultaneously a precise grain size control during austenitising is required. A homogenous former austenite grain size distribution results in a more uniform performance of the mechanical properties. This paper summarizes the results of recent research regarding the demands on steels for a high temperature carburising process. The possibility to prevent undesired grain growth by increasing the grain coarsening temperature using microalloying elements as well as the impact on the production process is discussed. (orig.)

The effect of the initial microstructure in terms of sink strength on the ion-irradiation-induced hardening of ODS alloys studied by nanoindentation

Science.gov (United States)

Duan, Binghuang; Heintze, Cornelia; Bergner, Frank; Ulbricht, Andreas; Akhmadaliev, Shavkat; Oñorbe, Elvira; de Carlan, Yann; Wang, Tieshan

2017-11-01

Oxide dispersion strengthened (ODS) Fe-Cr alloys are promising candidates for structural components in nuclear energy production. The small grain size, high dislocation density and the presence of particle matrix interfaces may contribute to the improved irradiation resistance of this class of alloys by providing sinks and/or traps for irradiation-induced point defects. The extent to which these effects impede hardening is still a matter of debate. To address this problem, a set of alloys of different grain size, dislocation density and oxide particle distribution were selected. In this study, three-step Fe-ion irradiation at both 300 °C and 500 °C up to 10 dpa was used to introduce damage in five different materials including three 9Cr-ODS alloys, one 14Cr-ODS alloy and one 14Cr-non-ODS alloy. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), small angle neutron scattering (SANS), and nanoindentation testing were applied, the latter before and after irradiation. Significant hardening occurred for all materials and temperatures, but it is distinctly lower in the 14Cr alloys and also tends to be lower at the higher temperature. The possible contribution of Cr-rich α‧-phase particles is addressed. The impact of grain size, dislocation density and particle distribution is demonstrated in terms of an empirical trend between total sink strength and hardening.

Microstructural evolution and strain hardening behavior of the cold-drawn austenitic stainless steels

International Nuclear Information System (INIS)

Choi, Jeom Yong; Jin, Won

1998-01-01

The strain induced α ' -martensite formation and the strain hardening behavior of metastable austenitic stainless steel during cold drawing have been investigated. The strain induced α ' -martensite nucleates mainly at the intersection of the mechanical twins rather than ε-martensite. It could be explained by the increase of stacking fault energy which arises from the heat generated during high speed drawing and, for AISI 304/Cu, the additional effect of Cu additions. The strain hardening behavior of austenitic stainless steel is strongly related to the microstructural evolution accompanied by strain induced α ' -martensite. The work hardening rates of cold-drawn 304 increased with increasing interstitial element(C,N) contents which affect the strength of the strain induced α ' -martensite

Characterization and Strain-Hardening Behavior of Friction Stir-Welded Ferritic Stainless Steel

Science.gov (United States)

Sharma, Gaurav; Dwivedi, Dheerendra Kumar; Jain, Pramod Kumar

2017-12-01

In this study, friction stir-welded joint of 3-mm-thick plates of 409 ferritic stainless steel (FSS) was characterized in light of microstructure, x-ray diffraction analysis, hardness, tensile strength, ductility, corrosion and work hardening properties. The FSW joint made of ferritic stainless steel comprises of three distinct regions including the base metal. In stir zone highly refined ferrite grains with martensite and some carbide precipitates at the grain boundaries were observed. X-ray diffraction analysis also revealed precipitation of Cr23C6 and martensite formation in heat-affected zone and stir zone. In tensile testing of the transverse weld samples, the failure eventuated within the gauge length of the specimen from the base metal region having tensile properties overmatched to the as-received base metal. The tensile strength and elongation of the longitudinal (all weld) sample were found to be 1014 MPa and 9.47%, respectively. However, in potentiodynamic polarization test, the corrosion current density of the stir zone was highest among all the three zones. The strain-hardening exponent for base metal, transverse and longitudinal (all weld) weld samples was calculated using various equations. Both the transverse and longitudinal weld samples exhibited higher strain-hardening exponents as compared to the as-received base metal. In Kocks-Mecking plots for the base metal and weld samples at least two stages of strain hardening were observed.

A brief review of cavity swelling and hardening in irradiated copper and copper alloys

International Nuclear Information System (INIS)

Zinkle, S.J.

1990-01-01

The literature on radiation-induced swelling and hardening in copper and its alloy is reviewed. Void formation does not occur during irradiation of copper unless suitable impurity atoms such as oxygen or helium are present. Void formation occurs for neutron irradiation temperatures of 180 to 550 degree C, with peak swelling occurring at ∼320 degree C for irradiation at a damage rate of 2 x 10 -7 dpa/s. The post-transient swelling rate has been measured to be ∼0.5%/dpa at temperatures near 400 degree C. Dispersion-strengthened copper has been found to be very resistant to void swelling due to the high sink density associated with the dispersion-stabilized dislocation structure. Irradiation of copper at temperatures below 400 degree C generally causes an increase in strength due to the formation of defect clusters which inhibit dislocation motion. The radiation hardening can be adequately described by Seeger's dispersed barrier model, with a barrier strength for small defect clusters of α ∼ 0.2. The radiation hardening apparently saturates for fluences greater than ∼10 24 n/m 2 during irradiation at room temperature due to a saturation of the defect cluster density. Grain boundaries can modify the hardening behavior by blocking the transmission of dislocation slip bands, leading to a radiation- modified Hall-Petch relation between yield strength and grain size. Radiation-enhanced recrystallization can lead to softening of cold-worked copper alloys at temperatures above 300 degree C

The characterization of Vicker's microhardness indentations and pile-up profiles as a strain-hardening microprobe

International Nuclear Information System (INIS)

Santos, C. Jr.

1998-04-01

Microhardness measurements have long been used to examine strength properties and changes in strength properties in metals, for example, as induced by irradiation. Microhardness affords a relatively simple test that can be applied to very small volumes of material. Microhardness is nominally related to the flow stress of the material at a fixed level of plastic strain. Further, the geometry of the pile-up of material around the indentation is related to the strain-hardening behavior of a material; steeper pile-ups correspond to smaller strain-hardening rates. In this study the relationship between pile-up profiles and strain hardening is examined using both experimental and analytical methods. Vickers microhardness tests have been performed on a variety of metal alloys including low alloy, high Cr and austenitic stainless steels. The pile-up topology around the indentations has been quantified using confocal microscopy techniques. In addition, the indentation and pile-up geometry has been simulated using finite element method techniques. These results have been used to develop an improved quantification of the relationship between the pile-up geometry and the strain-hardening constitutive behavior of the test material

Study of 16KhSN high strength steel in different structural states and under working conditions

International Nuclear Information System (INIS)

Skudnov, V.A.; Vorob'ev, I.A.; Kutyajkin, V.G.; Bugrov, Yu.V.

1985-01-01

A study was made on the effect of deformation degree (up to 60%) during reducing, drawing and heat treatment (annealing at 750 deg C), quenching from 930 deg C and tempering at 350 deg C) on strength, plasticity, hardening degree, notch sensitivity, density and elasticity characteristics of the steel. The effect of test temperature (from-196 up to 1000 deg C) on tensile strength and plasticity was studied as well. It was established that drawing and reducing of 16KhSN steel in annealed state with strain degrees of up to 60% results to increase of strength characteristics 1.7...2.3 times and decrease of plasticity characteristics by 15...23%, strain hardening coefficient - 2.2 times and the maximum strain energy - by 80 MJ/m 3 . Hardening heat treatment (quenching from 930 deg C+temperating at 350 deg C) affects on mechanical properties of 16KhSN steel in much the same way as cold working, but strength characteristics of heat-treated steel increase 2.6...3.6 times and the maximum strain energy grows by 640 MJ/m 3 . Systematic data on the effect of temperature (-196...1000 deg C) and tensile rate (4 mm/min...5m/s) on strength and plasticity of 16KhSN steel in annealed state were obtained

Measurements of Bauschinger effect and transient behavior of a quenched and partitioned advanced high strength steel

International Nuclear Information System (INIS)

Zang, Shun-lai; Sun, Li; Niu, Chao

2013-01-01

In recent decades, the needs for new advanced high strength steels (AHSS) with high ductility and strength have rapidly increased to achieve the targets of more fuel-efficient and safer vehicles in automotive industry. However, several undesirable phenomena are experimentally observed during the forming of such materials, particularly with complex loading and large plastic deformation. Springback is one of the most important problems that should be compensated in sheet metal forming process. In this paper, we investigated the hardening behavior of a Q and P (quench and partitioning) steel designated by QP980CR, which is a new third generation advance high strength steel, from the Baosteel Group Corp. in Shanghai, China. The uni-axial tensile and cyclic simple shear tests were conducted. The uni-axial tensile tests were performed on the specimens at 0°, 45° and 90° to rolling direction (RD). The flow stress and transverse strain evolution were obtained in view of the digital image correlation (DIC) measurement. The plastic anisotropy was optimized from the uni-axial tensile tests and thereafter incorporated into the simulations of cyclic simple shear tests. The cyclic simple shear tests were conducted with three prestrains to measure the Bauschinger effect, transient behavior and permanent softening, and to determine the material parameters of the combined isotropic-kinematic hardening model

Measurements of Bauschinger effect and transient behavior of a quenched and partitioned advanced high strength steel

Energy Technology Data Exchange (ETDEWEB)

Zang, Shun-lai, E-mail: shawn@mail.xjtu.edu.cn [School of Mechanical Engineering, Xi' an Jiaotong University, No. 28, Xianning Road, Xi' an, Shaanxi (China); Sun, Li [Manufacturing Process Research, General Motors China Science Lab, No. 56, Jinwan Road, Shanghai (China); Niu, Chao [School of Mechanical Engineering, Xi' an Jiaotong University, No. 28, Xianning Road, Xi' an, Shaanxi (China)

2013-12-01

In recent decades, the needs for new advanced high strength steels (AHSS) with high ductility and strength have rapidly increased to achieve the targets of more fuel-efficient and safer vehicles in automotive industry. However, several undesirable phenomena are experimentally observed during the forming of such materials, particularly with complex loading and large plastic deformation. Springback is one of the most important problems that should be compensated in sheet metal forming process. In this paper, we investigated the hardening behavior of a Q and P (quench and partitioning) steel designated by QP980CR, which is a new third generation advance high strength steel, from the Baosteel Group Corp. in Shanghai, China. The uni-axial tensile and cyclic simple shear tests were conducted. The uni-axial tensile tests were performed on the specimens at 0°, 45° and 90° to rolling direction (RD). The flow stress and transverse strain evolution were obtained in view of the digital image correlation (DIC) measurement. The plastic anisotropy was optimized from the uni-axial tensile tests and thereafter incorporated into the simulations of cyclic simple shear tests. The cyclic simple shear tests were conducted with three prestrains to measure the Bauschinger effect, transient behavior and permanent softening, and to determine the material parameters of the combined isotropic-kinematic hardening model.

Influence of Cooling Condition on the Performance of Grinding Hardened Layer in Grind-hardening

Science.gov (United States)

Wang, G. C.; Chen, J.; Xu, G. Y.; Li, X.

2018-02-01

45# steel was grinded and hardened on a surface grinding machine to study the effect of three different cooling media, including emulsion, dry air and liquid nitrogen, on the microstructure and properties of the hardened layer. The results show that the microstructure of material surface hardened with emulsion is pearlite and no hardened layer. The surface roughness is small and the residual stress is compressive stress. With cooling condition of liquid nitrogen and dry air, the specimen surface are hardened, the organization is martensite, the surface roughness is also not changed, but high hardness of hardened layer and surface compressive stress were obtained when grinding using liquid nitrogen. The deeper hardened layer grinded with dry air was obtained and surface residual stress is tensile stress. This study provides an experimental basis for choosing the appropriate cooling mode to effectively control the performance of grinding hardened layer.

Strain hardening behavior and microstructural evolution during plastic deformation of dual phase, non-grain oriented electrical and AISI 304 steels

Energy Technology Data Exchange (ETDEWEB)

Soares, Guilherme Corrêa; Gonzalez, Berenice Mendonça; Arruda Santos, Leandro de, E-mail: leandro.arruda@demet.ufmg.br

2017-01-27

Strain hardening behavior and microstructural evolution of non-grain oriented electrical, dual phase, and AISI 304 steels, subjected to uniaxial tensile tests, were investigated in this study. Tensile tests were performed at room temperature and the strain hardening behavior of the steels was characterized by three different parameters: modified Crussard–Jaoul stages, strain hardening rate and instantaneous strain hardening exponent. Optical microscopic analysis, X-ray diffraction measurements, phase quantification by Rietveld refinement and hardness tests were also carried out in order to correlate the microstructural and mechanical responses to plastic deformation. Distinct strain hardening stages were observed in the steels in terms of the instantaneous strain hardening exponent and the strain hardening rate. The dual phase and non-grain oriented steels exhibited a two-stage strain hardening behavior while the AISI 304 steel displayed multiple stages, resulting in a more complex strain hardening behavior. The dual phase steels showed a high work hardening capacity in stage 1, which was gradually reduced in stage 2. On the other hand, the AISI 304 steel showed high strain hardening capacity, which continued to increase up to the tensile strength. This is a consequence of its additional strain hardening mechanism, based on a strain-induced martensitic transformation, as shown by the X-ray diffraction and optical microscopic analyses.

Effect of Fibers and Filler Types on Fresh and Hardened Properties of Self-Compacting Concrete

Directory of Open Access Journals (Sweden)

Saeed K. Rejeb* , Majid Kh . N. Ayad A. M.

2014-04-01

Full Text Available This paper deals with studying the fresh and hardened properties of self-compacting concrete, by using three types of filler (silica fume, clinker powder & lime stone powder, and two types of fibers (steel & glass fibers with volume fractions of (0.5% and (0.1% respectively. For each type of fillers, the fresh properties are measured by using Slump test, J- ring and V- funnel, while hardened properties include the compressive strength, splitting tensile strength and flexural strength. The results show that adding fibers to the self-compacting concrete (SCC well reduces the workability and improves the hardened properties. Also, the study concluded that better workability is obtained by using (lime stone, silica fume and clinker powder as fillers, respectively. While the higher hardened properties are gained by using silica fume were rather than those of other types of fillers 

Energetic model of metal hardening

Directory of Open Access Journals (Sweden)

Ignatova O.N.

2011-01-01

Full Text Available Based on Bailey hypothesis on the link between strain hardening and elastic lattice defect energy this paper suggests a shear strength energetic model that takes into consideration plastic strain intensity and rate as well as softening related to temperature annealing and dislocation annihilation. Metal strain hardening was demonstrated to be determined only by elastic strain energy related to the energy of accumulated defects. It is anticipated that accumulation of the elastic energy of defects is governed by plastic work. The suggested model has a reasonable agreement with the available experimental data for copper up to P = 70 GPa , for aluminum up to P = 10 GPa and for tantalum up to P = 20 GPa.

The effect of initial microstructure on the final properties of press hardened 22MnB5 steels

International Nuclear Information System (INIS)

Järvinen, Henri; Isakov, Matti; Nyyssönen, Tuomo; Järvenpää, Martti; Peura, Pasi

2016-01-01

This paper addresses the relationship between initial microstructure and final properties of press hardened 22MnB5 steels. Four commercial 22MnB5 steels having different initial microstructures were investigated. An experimental press hardening equipment with a flat-die was used to investigate material behavior in the direct press hardening process. Two austenitizing treatments, 450 s and 180 s at 900 °C, were examined. Microstructural characterization with optical and scanning electron microscopes revealed a mixture of martensite and auto-tempered martensite after press hardening. Electron backscatter diffraction data of the transformed martensite was used to reconstruct grain boundary maps of parent austenite. Grain sizes of parent austenite (mean linear intercept) were measured for each material. In addition to microstructural evaluation, quasistatic and high strain rate tensile tests at strain rates of 5×10 −4 s −1 and 400 s −1 , respectively, were performed for press hardened samples. The results show that strength and uniform elongation depend on the initial microstructure of the 22MnB5 steel, when parameters typical to the direct press hardening process are used. Parent austenite grain size was shown to influence the morphology of the transformed martensite, which in turn affects the strength and uniform elongation after press hardening. The tensile properties of the press hardened materials are almost strain rate independent in the studied strain rate range. The obtained results can be used to optimize the properties of 22MnB5 steels in the direct press hardening process. In addition, the here revealed connection between the parent austenite grain size and final steel properties should be taken into account in the development of new press hardening steel grades for automotive industry.

The effect of initial microstructure on the final properties of press hardened 22MnB5 steels

Energy Technology Data Exchange (ETDEWEB)

Järvinen, Henri, E-mail: henri.jarvinen@tut.fi [Department of Materials Science, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland); Isakov, Matti; Nyyssönen, Tuomo [Department of Materials Science, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland); Järvenpää, Martti [SSAB Europe Oy, Harvialantie 420, FI-13300 Hämeenlinna (Finland); Peura, Pasi [Department of Materials Science, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland)

2016-10-31

This paper addresses the relationship between initial microstructure and final properties of press hardened 22MnB5 steels. Four commercial 22MnB5 steels having different initial microstructures were investigated. An experimental press hardening equipment with a flat-die was used to investigate material behavior in the direct press hardening process. Two austenitizing treatments, 450 s and 180 s at 900 °C, were examined. Microstructural characterization with optical and scanning electron microscopes revealed a mixture of martensite and auto-tempered martensite after press hardening. Electron backscatter diffraction data of the transformed martensite was used to reconstruct grain boundary maps of parent austenite. Grain sizes of parent austenite (mean linear intercept) were measured for each material. In addition to microstructural evaluation, quasistatic and high strain rate tensile tests at strain rates of 5×10{sup −4} s{sup −1} and 400 s{sup −1}, respectively, were performed for press hardened samples. The results show that strength and uniform elongation depend on the initial microstructure of the 22MnB5 steel, when parameters typical to the direct press hardening process are used. Parent austenite grain size was shown to influence the morphology of the transformed martensite, which in turn affects the strength and uniform elongation after press hardening. The tensile properties of the press hardened materials are almost strain rate independent in the studied strain rate range. The obtained results can be used to optimize the properties of 22MnB5 steels in the direct press hardening process. In addition, the here revealed connection between the parent austenite grain size and final steel properties should be taken into account in the development of new press hardening steel grades for automotive industry.

Comparison of Thermal Creep Strain Calculation Results Using Time Hardening and Strain Hardening Rules

International Nuclear Information System (INIS)

Kim, Junehyung; Cheon, Jinsik; Lee, Byoungoon; Lee, Chanbock

2014-01-01

One of the design criteria for the fuel rod in PGSFR is the thermal creep strain of the cladding, because the cladding is exposed to a high temperature for a long time during reactor operation period. In general, there are two kind of calculation scheme for thermal creep strain: time hardening and strain hardening rules. In this work, thermal creep strain calculation results for HT9 cladding by using time hardening and strain hardening rules are compared by employing KAERI's current metallic fuel performance analysis code, MACSIS. Also, thermal creep strain calculation results by using ANL's metallic fuel performance analysis code, LIFE-METAL which adopts strain hardening rule are compared with those by using MACSIS. Thermal creep strain calculation results for HT9 cladding by using time hardening and strain hardening rules were compared by employing KAERI's current metallic fuel performance analysis code, MACSIS. Also, thermal creep strain calculation results by using ANL's metallic fuel performance analysis code, LIFE-METAL which adopts strain hardening rule were compared with those by using MACSIS. Tertiary creep started earlier in time hardening rule than in strain hardening rule. Also, calculation results by MACSIS with strain hardening and those obtained by using LIFE-METAL were almost identical to each other

Microstructural evolution at high strain rates in solution-hardened interstitial free steels

International Nuclear Information System (INIS)

Uenishi, A.; Teodosiu, C.; Nesterova, E.V.

2005-01-01

Comprehensive transmission electron microscopical studies have been conducted for solution-hardened steels deformed at high (1000 s -1 ) and low (0.001 s -1 ) strain rates, in order to clarify the effects of strain rate and a jump in strain rate on the evolution of the microstructure and its connection with the mechanical response. It was revealed that the various types of microstructure, observed even within the same specimen, depend on the corresponding grain orientations and their evolution with progressive deformation depends on these microstructure types. At high strain rates, the dislocation density increases especially at low strains and the onset of dislocation organization is delayed. A jump in strain rate causes an increase of the dislocation density inside an organized structure. These results corroborated the mechanical behaviour at high strain rates after compensation for the cross-sectional reduction and temperature increase. The higher work-hardening rate at high strain rates could be connected to a delay in the dislocation organization. The high work-hardening rate just after a jump could be due to an increase of the density of dislocations distributed uniformly inside an organized structure

Boundary and sub-boundary hardening in high-Cr ferritic steels during long-term creep at 650 C

Energy Technology Data Exchange (ETDEWEB)

Abe, F. [National Institute for Materials Science (NIMS) (Japan)

2008-07-01

The sub-boundary hardening is shown to be the most important strengthening mechanism in creep of the 9% Cr steel base metal and welded joints. The addition of boron reduces the coarsening rate of M{sub 23}C{sub 6} carbides along boundaries near prior austenite grain boundaries during creep, enhancing the sub-boundary hardening. This improves long-term creep strength. The enhancement of boundary and subboundary hardening by fine distribution of precipitates along boundaries is significantly reduced in fine-grained region of Ac{sub 3} HAZ simulated specimens of conventional steels P92 and P122. In NIMS 9% Cr boron steel welded joints, the grain size and distribution of carbonitrides are substantially the same between the HAZ and base metal, where fine carbonitrides are distributed along the lath and block boundaries as well as along prior austenite grain boundaries. This is essential for the suppression of Type IV fracture in NIMS 9% Cr boron steel welded joints. (orig.)

Heavyweight cement concrete with high stability of strength parameters

Science.gov (United States)

Kudyakov, Konstantin; Nevsky, Andrey; Danke, Ilia; Kudyakov, Aleksandr; Kudyakov, Vitaly

2016-01-01

The present paper establishes regularities of basalt fibers distribution in movable cement concrete mixes under different conditions of their preparation and their selective introduction into mixer during the mixing process. The optimum content of basalt fibers was defined as 0.5% of the cement weight, which provides a uniform distribution of fibers in the concrete volume. It allows increasing compressive strength up to 51.2% and increasing tensile strength up to 28.8%. Micro-structural analysis identified new formations on the surface of basalt fibers, which indicates the good adhesion of hardened cement paste to the fibers. Stability of concrete strength parameters has significantly increased with introduction of basalt fibers into concrete mix.

ANALISIS ARAH DAN PERLAKUAN SERAT TAPIS SERTA RASIO EPOXY HARDENER TERHADAP SIFAT FISIS DAN MEKANIS KOMPOSIT TAPIS/EPOXY

Directory of Open Access Journals (Sweden)

Putu Lokantara

2012-11-01

Full Text Available Tapis kelapa (Coconut filter as natural fiber, in this time its resources very copius but no longer be exploited and thrown off hand as waste though in fact its used for other material dissimilar inovatif and high economic valuable that is as one of natural fiber alternative to be composite. The objective of this research is to investigate the behavior changing of physical and mechanical properties of composite tapis kelapa as reinforcement and epoxy 7120 with hardener Versamid 140 as matrix. The fiber is treated with the chemical NaOH and KMnO4 with percentage 0.5%, 1%, and 2% in weight, respectively. The ratio of epoxy and hardener is 7:3 and 6:4, and fiber orientation 0o, 45o, dan 90o. For testing of the speciment in tensile test with ASTM standard D3039 and three point bending test with ASTM standard D790. The result of this research obtained that fiber treatment with KMnO4 give the better effect to machine properties compared to NaOH. Variation of percentage 0.5%, 1%, and 2% NaOH and KMnO4 give the effect in fiber surface which higher percentage make the cleaner of surface, decrease of wax contain, and roughness of fiber surface so that stronger of linkage of fiber and matrix and increase of tensile strength, bending strength, and bending modulus of the composite. The highest tensile strength, modulus of elasticity and bending strength are 70.23 MPa, 446.24 GPa and 97.81 MPa respectively reached at composite with ratio epoxy/hardener 7:3; by 2% KMnO4 and fiber orientation 45o. While the highest modulus of elasticity is 385.48 GPa reached at composite with the ratio epoxy/hardener 6:4; 2% KMnO4 and fiber orientation 90o. Keywords: Tensile Strength, bending strength, ratio of epoxy/hardener, NaOH, KMnO4

Micromilling of hardened tool steel for mould making applications

DEFF Research Database (Denmark)

Bissacco, Giuliano; Hansen, Hans Nørgaard; De Chiffre, Leonardo

2005-01-01

geometries as those characterizing injection moulding moulds. The realization of the micromilling process in connection with hardened tool steel as workpiece material is particularly challenging. The low strength of the miniaturized end mills implies reduction and accurate control of the chip load which...... wear. This paper presents the micromilling process applied to the manufacturing of micro injection moulding moulds in hardened tool steel, presenting experimental evidence and possible solutions to the above-mentioned issues....

Microstructure-property relationships and constitutive response of plastically graded case hardened steels

Science.gov (United States)

Klecka, Michael A.

Case hardened materials, popularly used in many demanding engineering applications such as bearings, gears, and wear/impact surfaces, have high surface hardness and a gradient in material properties (hardness, yield strength, etc.) as a function of depth; therefore, they behave as plastically graded materials. In the current study, two different commercially available case carburized steels along with two through hardened steels are characterized to obtain relationships among the volume fraction of subsurface carbides, indentation hardness, elastic modulus, and yield strength as a function of depth. A variety of methods including microindentation, nanoindentation, ultrasonic measurements, compression testing, rule of mixtures, and upper and lower bound models are used to determine the relationships for elastic modulus and compare the experimental results with model predictions. In addition, the morphology, composition, and properties of the carbide particles are also determined. The gradient in hardness with depth in graded materials is commonly determined using microindentation on the cross-section of the material which contains the gradation in microstructure or composition. In the current study, a novel method is proposed to predict the hardness gradient profile using solely surface indentations at a range of loads. The method does not require the graded material to be sectioned, and has practical utility in the surface heat-treatment industry. For a material with a decreasing gradient in hardness, higher indent loads result in a lower measured hardness due to the influence of the softer subsurface layers. A power-law model is presented which relates the measured surface indentation hardness under increasing load to the subsurface gradient in hardness. A coordinated experimental and numerical study is presented to extract the constitutive response of graded materials, utilizing relationships between hardness, plastic deformation, and strain hardening response

Influence of bagasse ash and recycled concrete aggregate on hardened properties of high-strength concrete

Directory of Open Access Journals (Sweden)

P. Rattanachu

2018-04-01

Full Text Available This research aimed to use of bagasse ash as a cement replacement in high-strength recycled aggregate concrete (HS-RAC. Crushed limestone was replaced with 100% recycled concrete aggregate (RCA and the ground bagasse ash (GBA was used to partially replace ordinary Portland cement (OPC at 20, 35 and 50%wt of binder to cast HS-RAC. The results indicated that the replacing of crushed limestone with RCA had a negative impact on the properties of the concrete. Increasing the amount of GBA in HS-RAC resulted in a decrease in density and an increase in the volume of permeable pore space. The concrete mixtures prepared with 20%wt GBA replacement of OPC promoted greater the compressive strength than the conventional concrete (CT concrete at 90 days or more. HS-RAC with GBA (up to 50% was more durable in terms of chloride ion penetration resistance, although it had lower compressive strength than the CT concrete.

Modeling and Analysis of Deformation for Spiral Bevel Gear in Die Quenching Based on the Hardenability Variation

Science.gov (United States)

Zhang, Yingtao; Wang, Gang; Shi, Wankai; Yang, Lin; Li, Zhichao

2017-07-01

Spiral bevel gears are widely used to transmit energy between intersecting axes. The strength and fatigue life of the gears are improved by carburizing and quenching. A die quenching process is used to control the deformation of the gear. The deformation is determined by the variations in the hardenability for a certain die quenching process. The relationship between hardenability, phase transformation and deformation needs to be studied to minimize deformation during the adjustment of the die quenching process parameters. In this paper, material properties for 22CrMoH steel are determined by the results of Jominy tests, dilatometry experiments and static mechanical property tests. The material models were built based on testing results under the consideration of hardenability variation. An finite element analysis model was developed to couple the phase transformation and deformation history of the complete carburizing and die quenching process for the spiral bevel gears. The final microstructures in the gear were bainite for low hardenability steel and a mixture of bainite and ferrite for high hardenability steel. The largest buckling deformation at the gear bottom surface is 0.375 mm at the outer circle for the low hardenability gear and 0.091 mm at the inner circle for the high hardenability gear.

Influence of Glass Fiber on Fresh and Hardened Properties of Self Compacting Concrete

Science.gov (United States)

Bharathi Murugan, R.; Haridharan, M. K.; Natarajan, C.; Jayasankar, R.

2017-07-01

The practical need of self-compacting concrete (SCC) is increasing due to increase in the infrastructure competence all over the world. The effective way of increasing the strength of concrete and enhance the behaviour under extreme loading (fire) is the keen interest. Glass fibers were added for five different of volume fractions (0%, 0.1%, 0.3%, 0.5% and 0.6%) to determine the optimum percentage of glass fiber without compensating the fresh properties and enhanced hardened properties of SCC concrete. The fresh state of concrete is characterized by slump flow, T-50cm slump flow, and V-funnel and L- box tests. The results obtained in fresh state are compared with the acceptance criteria of EFNARC specification. Concrete specimens were casted to evaluate the hardened properties such as compressive strength, split tensile strength, flexural strength and modulus of elasticity. Incorporation the glass fiber into SCC reduces the workability but within the standard specification. The hardened properties of SCC glass fiber reinforced concrete were enhanced, due to bridging the pre-existing micro cracks in concrete by glass fiber addition.

Fatigue crack Behaviour in a High Strength Tool Steel

DEFF Research Database (Denmark)

Højerslev, Christian; Carstensen, Jesper V.; Brøndsted, Povl

2002-01-01

The influence of microstructure on fatigue crack initiation and crack growth of a hardened and tempered high speed steel was investigated. The evolution of fatigue cracks was followed in four point bending at room temperature. It was found that a carbide damage zone exists above a threshold load...... value of maximally 80% of the yield strength of the steel. The size of this carbide damage zone increases with increasing load amplitude, and the zone is apparently associated with crack nucleation. On fatigue crack propagation plastic deformation of the matrix occurs in a radius of approximately 4...... microns in front of the fatigue crack tip, which is comparable with the relevant mean free carbide spacing....

On residual stresses and fatigue of laser hardened steels

International Nuclear Information System (INIS)

Lin, Ru.

1992-01-01

This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10 7 cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au)

On residual stresses and fatigue of laser hardened steels

Energy Technology Data Exchange (ETDEWEB)

Lin, Ru.

1992-01-01

This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10[sup 7] cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au).

Evaluation of the Chemical and Mechanical Properties of Hardening High-Calcium Fly Ash Blended Concrete.

Science.gov (United States)

Fan, Wei-Jie; Wang, Xiao-Yong; Park, Ki-Bong

2015-09-07

High-calcium fly ash (FH) is the combustion residue from electric power plants burning lignite or sub-bituminous coal. As a mineral admixture, FH can be used to produce high-strength concrete and high-performance concrete. The development of chemical and mechanical properties is a crucial factor for appropriately using FH in the concrete industry. To achieve sustainable development in the concrete industry, this paper presents a theoretical model to systematically evaluate the property developments of FH blended concrete. The proposed model analyzes the cement hydration, the reaction of free CaO in FH, and the reaction of phases in FH other than free CaO. The mutual interactions among cement hydration, the reaction of free CaO in FH, and the reaction of other phases in FH are also considered through the calcium hydroxide contents and the capillary water contents. Using the hydration degree of cement, the reaction degree of free CaO in FH, and the reaction degree of other phases in FH, the proposed model evaluates the calcium hydroxide contents, the reaction degree of FH, chemically bound water, porosity, and the compressive strength of hardening concrete with different water to binder ratios and FH replacement ratios. The evaluated results are compared to experimental results, and good consistencies are found.

Influence of microstructure of high-strength low-alloy steels on their weldability

International Nuclear Information System (INIS)

Cwiek, J.; Labanowski, J.

2003-01-01

Microstructure of steel before welding has influence on the steel's susceptibility to cold cracking because it influences hardenability and maximum hardness of heat affected zone (HAZ). Two high-strength low-alloy (HSLA) steel grades 18G2AV and 14HNMBCu, in various heat treatment conditions, were subjected to simulated welding thermal cycles. It was revealed that maximum HAZ hardness is influenced by microstructure presented before thermal cycle was applied. The higher HAZ hardness was observed for quenched and tempered condition, comparing to full annealed and overheated conditions. (author)

The effect of voids on the hardening of body-centered cubic Fe

Energy Technology Data Exchange (ETDEWEB)

Nakai, Ryosuke, E-mail: ryosuke.nakai@jupiter.qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Yabuuchi, Kiyohiro, E-mail: k-yabuuchi@iae.kyoto-u.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan); Nogami, Shuhei, E-mail: shuhei.nogami@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Hasegawa, Akira, E-mail: akira.hasegawa@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan)

2016-04-01

The mechanical properties of metals are affected by various types of defects. Hardening is usually described through the interaction between dislocations and obstacles, in the so-called line tension theory. The strength factor in the line tension theory represents the resistance of a defect against the dislocation motion. In order to understand hardening from the viewpoint of the microstructure, an accurate determination of the strength factor of different types of defects is essential. In the present study, the strength factor of voids in body-centered cubic (BCC) Fe was investigated by two different approaches: one based on the Orowan equation to link the measured hardness with the average size and density of voids, and the other involving direct observation of the interaction between dislocations and voids by transmission electron microscope (TEM). The strength factor of voids induced by ion irradiation estimated by the Orowan equation was 0.6, whereas the strength factor estimated by the direct TEM approach was 0.8. The difference in the strength factors measured by the two approaches is due to the positional relationship between dislocations and voids: the central region of a void is stronger than the tip. Moreover, the gliding plane and the direction of dislocation may also affect the strength factor of voids. This study determined the strength factor of voids in BCC Fe accurately, and suggested that the contribution of voids to the irradiation hardening is larger than that of dislocation loops and Cu-rich precipitates. - Highlights: • The strength factor of voids in BCC Fe was experimentally investigated. • The strength factor of voids estimated by the line tension theory was 0.6. • The strength factor of voids estimated by the bowing angle of dislocations was 0.8. • The different strength factors are due to the positional relationship.

Phase evolution and mechanical behavior of 0.36 wt% C high strength TRIP-assisted steel

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Swarup Kumar; Chattopadhyay, Partha Protim [Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711 103 (India)

2012-12-15

Phase evolution in a 0.36 wt% C steel has been studied by thermodynamic calculation and dilatometric analysis with an aim to achieve high strength TRIP-assisted steel with bainitic microstructure. The equilibrium phase fraction calculated as the function of temperature indicated the formation of {delta}-ferrite ({approx}98%) at 1417 C. In contrast, similar calculation under para-equilibrium condition exhibited transformation of {delta}-ferrite to austenite at the temperature below 1300 C. During further cooling two-phase ({alpha}+{gamma}) microstructure has been found to be stable at the intercritical temperature range. The experimentally determined CCT diagram has revealed that adequate hardenability is achievable in the steel under continuous cooling condition at cooling rate >5 C s{sup -1}. In view of the aforesaid results, the steel has been hot rolled and subjected to different process schedule conducive to the evolution of bainitic microstructure. The hot rolled steel has exhibited reasonably good tensile properties. However, cold deformation of the hot rolled sample followed by intercritical annealing and subsequent isothermal bainitic transformation has resulted in high strength (>1000 MPa) with attractive elongation due to the favorable work hardening condition during plastic deformation offered by the multiphase microstructure. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Age-hardening susceptibility of high-Cr ODS ferritic steels and SUS430 ferritic steel

Energy Technology Data Exchange (ETDEWEB)

Chen, Dongsheng, E-mail: chen.dongsheng85@gmail.com [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kimura, Akihiko; Han, Wentuo; Je, Hwanil [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

2015-10-15

Highlights: • The role of oxide particles in α/α′ phase decomposition behavior; microstructure of phase decomposition observed by TEM. • The characteristics of ductility loss caused by age-hardening. • Correlation of phase decomposition and age-hardening explained by dispersion strengthened models. • Age-hardening susceptibility of ODS steels and SUS430 steel. - Abstract: The effect of aging on high-Cr ferritic steels was investigated with focusing on the role of oxide particles in α/α′ phase decomposition behavior. 12Cr-oxide dispersion strengthened (ODS) steel, 15Cr-ODS steel and commercial SUS430 steel were isothermally aged at 475 °C for up to 10,000 h. Thermal aging caused a larger hardening in SUS430 than 15Cr-ODS, while 12Cr-ODS showed almost no hardening. A characteristic of the ODS steels is that the hardening was not accompanied by the significant loss of ductility that was observed in SUS430 steel. After aging for 2000 h, SUS430 steel shows a larger ductile–brittle transition temperature (DBTT) shift than 15Cr-ODS steel, which suggests that the age-hardening susceptibility is lower in 15Cr-ODS steel than in conventional SUS430 steel. Thermal aging leaded to a large number of Cr-rich α′ precipitates, which were confirmed by transmission electron microscopy (TEM). Correlation of age-hardening and phase decomposition was interpreted by Orowan type strengthening model. Results indicate that oxide particles cannot only suppress ductility loss, but also may influence α/α′ phase decomposition kinetics.

Role of grain refinement in hardening of structural steels at preliminary thermomechanical treatment

International Nuclear Information System (INIS)

Bukhvalov, A.B.; Grigor'eva, E.V.; Davydova, L.S.; Degtyarev, M.V.; Levit, V.I.; Smirnova, N.A.; Smirnov, L.V.

1981-01-01

The hardening mechanism during preliminary thermomechanical treatment with deformation by cold rolling or hydroextrusion is studied on structural 37KhN3M1 and 38KhN3MFA steels. Specimens have been tested on static tension, impact strength and fracture toughness. It is shown that hydroextrusion application instead of rolling does not change the hardening effect of preliminary thermomechanical treatment (PTMT). It is established that the increase of preliminary deformation degree and the use of accelerated short term hardening heating provides a bett er grain refinement and the increase of PTMT hardening effect [ru

Local buckling failure analysis of high-strength pipelines

Institute of Scientific and Technical Information of China (English)

Yan Li; Jian Shuai; Zhong-Li Jin; Ya-Tong Zhao; Kui Xu

2017-01-01

Pipelines in geological disaster regions typically suffer the risk of local buckling failure because of slender structure and complex load.This paper is meant to reveal the local buckling behavior of buried pipelines with a large diameter and high strength,which are under different conditions,including pure bending and bending combined with internal pressure.Finite element analysis was built according to previous data to study local buckling behavior of pressurized and unpressurized pipes under bending conditions and their differences in local buckling failure modes.In parametric analysis,a series of parameters,including pipe geometrical dimension,pipe material properties and internal pressure,were selected to study their influences on the critical bending moment,critical compressive stress and critical compressive strain of pipes.Especially the hardening exponent of pipe material was introduced to the parameter analysis by using the Ramberg-Osgood constitutive model.Results showed that geometrical dimensions,material and internal pressure can exert similar effects on the critical bending moment and critical compressive stress,which have different,even reverse effects on the critical compressive strain.Based on these analyses,more accurate design models of critical bending moment and critical compressive stress have been proposed for high-strength pipelines under bending conditions,which provide theoretical methods for highstrength pipeline engineering.

Influence of Binding Rates on Strength Properties of Moulding Sands with the GEOPOL Binder

Directory of Open Access Journals (Sweden)

Holtzer M.

2014-03-01

Full Text Available The results of investigations of moulding sands with an inorganic binder called GEOPOL, developed by the SAND TEAM Company are presented in the paper. Hardeners of various hardening rates are used for moulding sands with this binder. The main aim of investigations was determination of the influence of the hardening rate of moulding sands with the GEOPOL binder on technological properties of these sands (bending strength, tensile strength, permeability and grindability. In addition, the final strength of moulding sands of the selected compositions was determined by two methods: by splitting strength and shear strength measurements. No essential influence of the hardening rate on such parameters as: permeability, grindability and final strength was found. However, the sand in which the slowest hardener (SA 72 were used, after 1 hour of holding, had the tensile and bending strength practically zero. Thus, the time needed for taking to pieces the mould made of such moulding sand will be 1.5 - 2 hours.

RHOBOT: Radiation hardened robotics

Energy Technology Data Exchange (ETDEWEB)

Bennett, P.C.; Posey, L.D. [Sandia National Labs., Albuquerque, NM (United States)

1997-10-01

A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

RHOBOT: Radiation hardened robotics

International Nuclear Information System (INIS)

Bennett, P.C.; Posey, L.D.

1997-10-01

A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program

Plasma Methods of Obtainment of Multifunctional Composite Materials, Dispersion-Hardened by Nanoparticles

Science.gov (United States)

Sizonenko, O. N.; Grigoryev, E. G.; Pristash, N. S.; Zaichenko, A. D.; Torpakov, A. S.; Lypian, Ye. V.; Tregub, V. A.; Zholnin, A. G.; Yudin, A. V.; Kovalenko, A. A.

2017-09-01

High voltage electric discharge (HVED) in disperse system "hydrocarbon liquid - powder" due to impact of plasma discharge channel, electromagnetic fields, shock waves mechanical impact, hydro flows and volume microcavitation leads to synthesis of nanocarbon, metal powders dispersion and synthesis of micro- (from 10-6 to 10-7 m) and nanosized (from 10-7 to 10-9 m) composite powders of hardening phases. Spark plasma sintering (SPS) of powder mixtures allows targeted control of grain growth rate and thus allows obtainment of multifunctional composite materials dispersion hardened by nanoparticles. Processes of HVED synthesis of micro- and nanosized powders of new compositions from elemental metal powders and their mixtures with the subsequent application of high-speed SPS of obtained powders create conditions for increase of strength (by 10-20 %), hardness and wear-resistance (by 30-60 %) of obtained materials.

Strain hardening rate sensitivity and strain rate sensitivity in TWIP steels

Energy Technology Data Exchange (ETDEWEB)

Bintu, Alexandra [TEMA, Department of Mechanical Engineering, University of Aveiro, Campus Universitário de Santiago, 3810-193 (Portugal); Vincze, Gabriela, E-mail: gvincze@ua.pt [TEMA, Department of Mechanical Engineering, University of Aveiro, Campus Universitário de Santiago, 3810-193 (Portugal); Picu, Catalin R. [Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Lopes, Augusto B. [CICECO, Department of Materials and Ceramic Engineering, University of Aveiro, Campus Universitário de Santiago, 3810-193 (Portugal); Grácio, Jose J. [TEMA, Department of Mechanical Engineering, University of Aveiro, Campus Universitário de Santiago, 3810-193 (Portugal); Barlat, Frederic [Materials Mechanics Laboratory, Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

2015-04-01

TWIP steels are materials with very high strength and exceptional strain hardening capability, parameters leading to large energy absorption before failure. However, TWIP steels also exhibit reduced (often negative) strain rate sensitivity (SRS) which limits the post-necking deformation. In this study we demonstrate for an austenitic TWIP steel with 18% Mn a strong dependence of the twinning rate on the strain rate, which results in negative strain hardening rate sensitivity (SHRS). The instantaneous component of SHRS is large and negative, while its transient is close to zero. The SRS is observed to decrease with strain, becoming negative for larger strains. Direct observations of the strain rate dependence of the twinning rate are made using electron microscopy and electron backscatter diffraction, which substantiate the proposed mechanism for the observed negative SHRS.

Strain hardening rate sensitivity and strain rate sensitivity in TWIP steels

International Nuclear Information System (INIS)

Bintu, Alexandra; Vincze, Gabriela; Picu, Catalin R.; Lopes, Augusto B.; Grácio, Jose J.; Barlat, Frederic

2015-01-01

TWIP steels are materials with very high strength and exceptional strain hardening capability, parameters leading to large energy absorption before failure. However, TWIP steels also exhibit reduced (often negative) strain rate sensitivity (SRS) which limits the post-necking deformation. In this study we demonstrate for an austenitic TWIP steel with 18% Mn a strong dependence of the twinning rate on the strain rate, which results in negative strain hardening rate sensitivity (SHRS). The instantaneous component of SHRS is large and negative, while its transient is close to zero. The SRS is observed to decrease with strain, becoming negative for larger strains. Direct observations of the strain rate dependence of the twinning rate are made using electron microscopy and electron backscatter diffraction, which substantiate the proposed mechanism for the observed negative SHRS

Laser Welding of Coated Press-hardened Steel 22MnB5

Science.gov (United States)

Siltanen, Jukka; Minkkinen, Ari; Järn, Sanna

The press-hardening process is widely used for steels that are used in the automotive industry. Using ultra-high-strength steels enables car manufacturers to build lighter, stronger, and safer vehicles at a reduced cost and generating lower CO2 emissions. In the study, laser welding properties of the coated hot stamped steel 22BMn5 were studied. A constant 900 °C temperature was used to heat the steel plates, and two different furnace times were used in the press-hardening, being 300 and 740 seconds. Some of the plates were shot blasted to see the influence of the partly removed oxide layer on the laser welding and quality. The welding set-up, welding, and testing of the weld specimens complied with the automotive testing code SEP 1220.

Mechanical properties and fatigue strength of high manganese non-magnetic steel/carbon steel welded joints

International Nuclear Information System (INIS)

Nakaji, Eiji; Ikeda, Soichi; Kim, You-Chul; Nakatsuji, Yoshihiro; Horikawa, Kosuke.

1997-01-01

The dissimilar materials welded joints of high manganese non-magnetic steel/carbon steel (hereafter referred to as DMW joints), in which weld defects such as hot crack or blowhole are not found, were the good quality. Tensile strength of DMW joints was 10% higher than that of the base metal of carbon steel. In the bend tests, the DMW joints showed the good ductility without crack. Charpy absorbed energy at 0(degC) of the DMW joints was over 120(J) in the bond where it seems to be the lowest. Large hardening or softening was not detected in the heat affected zone. Fatigue strength of the DMW joints is almost the same with that of the welded joints of carbon steel/carbon steel. As the fatigue strength of the DMW joints exceeds the fatigue design standard curve of JSSC for carbon steel welded joints, the DMW joints can be treated the same as the welded joints of carbon steel/carbon steel of which strength is lower than that of high manganese non-magnetic steel, from the viewpoint of the fatigue design. (author)

Compressive strength of concrete and mortar containing fly ash

Science.gov (United States)

Liskowitz, John W.; Wecharatana, Methi; Jaturapitakkul, Chai; Cerkanowicz, deceased, Anthony E.

1997-01-01

The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention includes a method for predicting the compressive strength of such a hardenable mixture, which is very important for planning a project. The invention also relates to hardenable mixtures comprising cement and fly ash which can achieve greater compressive strength than hardenable mixtures containing only concrete over the time period relevant for construction. In a specific embodiment, a formula is provided that accurately predicts compressive strength of concrete containing fly ash out to 180 days. In other specific examples, concrete and mortar containing about 15% to 25% fly ash as a replacement for cement, which are capable of meeting design specifications required for building and highway construction, are provided. Such materials can thus significantly reduce construction costs.

Ultrafine Structure and High Strength in Cold-Rolled Martensite

DEFF Research Database (Denmark)

Huang, Xiaoxu; Morito, S.; Hansen, Niels

2012-01-01

Structural refinement by cold rolling (10 to 80 pct reductions) of interstitial free (IF) steel containing Mn and B has been investigated from samples with different initial structures: (a) lath martensite, (b) coarse ferrite (grain size 150 mu m), and (c) fine ferrite (22 mu m). Unalloyed IF steel....... At low to medium strains, lath martensite transforms into a cell block structure composed of cell block boundaries and cell boundaries with only a negligible change in strength. At medium to large strains, cell block structures in all samples refine with increasing strain and the hardening rate...... is constant (stage IV). A strong effect of the initial structure is observed on both the structural refinement and the strength increase. This effect is largest in lath martensite and smallest in unalloyed ferrite. No saturation in structural refinement and strength is observed. The discussion covers...

Influence of the Hardener on the Emission of Harmful Substances from Moulding Sands with Furan Resin in the Pyrolysis Process

OpenAIRE

Holtzer M.; Kmita A.; Żymankowska-Kumon S.; Bobrowski A.; Dańko R.

2016-01-01

The furan resin offers advantages such as high intensity, low viscosity, good humidity resistance and is suitable for cast different casting alloys: steel, cast iron and non-ferrous metal casting. For hardening furan resins are used different hardeners (acid catalysts). The acid catalysts have significant effects on the properties of the cured binder (e,g. binding strength and thermal stability) [1 - 3]. Investigations of the gases emission in the test foundry plant were performed according t...

Behavior of surface residual stress in explosion hardened high manganese austenitic cast steel due to repeated impact loads

International Nuclear Information System (INIS)

Oda, Akira; Miyagawa, Hideaki

1985-01-01

Explosion hardened high manganese austenitic cast steel is being tried for rail crossing recently. From the previous studies, it became clear that high tensile residual stress was generated in the hardened surface layer by explosion and microcracks were observed. In this study, therefore, the behavior of surface residual stress in explosion hardened steel due to repeated impact loads was examined and compared with those of the original and shot peened steels. The results obtained are summarized as follows: (1) In the initial stage of the repetition of impact, high tensile surface residual stress in explosion hardened steel decreased rapidly with the repetition of impact, while those of the original and shot peened steels increased rapidly. This difference was attributed to the difference in depth of the work hardened layer in three testing materials. (2) Beyond 20 impacts the residual stress of three test specimens decreased gradually, and at more than 2000 impacts the compressive stress of about 500 MPa was produced regardless of the histories of working of testing materials. (3) The linear law in the second stage of residual stress fading was applicable to this case, and the range of the linear relationship was related to the depth of the work hardened layer of testing material. (4) From the changes in half-value breadth and peak intensity of diffraction X-ray, it was supposed that a peculiar microscopic strain exists in explosion hardened steel. (author)

Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling

Science.gov (United States)

Liu, Chong-yu; Yu, Peng-fei; Wang, Xiao-ying; Ma, Ming-zhen; Liu, Ri-ping

2014-07-01

An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560°C for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180°C. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420°C, and then increased; the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180°C rolling water-quenched alloy were also improved by the presence of β″ phase. Above 420°C, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.

Development of Bake Hardening Effect by Plastic Deformation and Annealing Conditions

Directory of Open Access Journals (Sweden)

Kvačkaj, T.

2006-01-01

Full Text Available The paper deals with the classification of steel sheets for automotives industry on the basis of strength and structural characteristics. Experimental works were aimed to obtain the best possible strengthening parameters as well as work hardening and solid solution ferrite hardening, which are the result of thermal activation of interstitial carbon atoms during paint-baking of auto body. Hardening process coming from interstitial atoms is realized as two-step process. The first step is BH (bake hardening effect achieved by interaction of interstitial atoms with dislocations. The Cottrels atmosphere is obtained. The second step of BH effect is to produced the hardening from precipitation of the carbon atoms in e-carbides, or formation of Fe32C4 carbides. WH (work hardening effect is obtained as dislocation hardening from plastic deformations during sheet deep drawing. Experimental works were aimed at as to achieve such plastic material properties after cold rolling, annealing and skin-pass rolling, which would be able to classify the material ZStE220BH into the drawing categories at the level of DQ – DDQ. As resulting from the experimental results, the optimal treatment conditions for the maximal sum (WH+BH = 86 MPa are as follows: total cold rolling deformation ecold = 65 %, annealing temperature Tanneal. = 700 °C.

Strain hardening of cold-rolled lean-alloyed metastable ferritic-austenitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

Papula, Suvi [Aalto University School of Engineering, Department of Mechanical Engineering, P.O. Box 14200, FI-00076 Aalto (Finland); Anttila, Severi [Centre for Advanced Steels Research, University of Oulu, P.O. Box 4200, 90014 Oulu (Finland); Talonen, Juho [Outokumpu Oyj, P.O. Box 245, FI-00181 Helsinki (Finland); Sarikka, Teemu; Virkkunen, Iikka; Hänninen, Hannu [Aalto University School of Engineering, Department of Mechanical Engineering, P.O. Box 14200, FI-00076 Aalto (Finland)

2016-11-20

Mechanical properties and strain hardening of two pilot-scale lean-alloyed ferritic-austenitic stainless steels having metastable austenite phase, present at 0.50 and 0.30 volume fractions, have been studied by means of tensile testing and nanoindentation. These ferritic-austenitic stainless steels have high strain-hardening capacity, due to the metastable austenite phase, which leads to an improved uniform elongation and higher tensile strength in comparison with most commercial lean duplex stainless steels. According to the results, even as low as 0.30 volume fraction of austenite seems efficient for achieving nearly 40% elongation. The austenite phase is initially the harder phase, and exhibits more strain hardening than the ferrite phase. The rate of strain hardening and the evolution of the martensite phase were found to depend on the loading direction: both are higher when strained in the rolling direction as compared to the transverse direction. Based on the mechanical testing, characterization of the microstructure by optical/electron microscopy, magnetic balance measurements and EBSD texture analysis, this anisotropy in mechanical properties of the cold-rolled metastable ferritic-austenitic stainless steels can be explained by the elongated dual-phase microstructure, fiber reinforcement effect of the harder austenite phase and the presence and interplay of rolling textures in the two phases.

Effect of hardening methods of moulding sands with water glass on structure of bonding bridges

Directory of Open Access Journals (Sweden)

M. Stachowicz

2010-07-01

Full Text Available Research on influence of hardening methods on structure of bonding bridges in moulding sands with sodium water glass is presented.Moulding sands with addition of 2.5 % of binder with molar module 2.0 were hardened with CO2 and dried in traditional way or hardenedwith microwaves. It was proved that the hardening method affects structure of bonding bridges, correlating with properties of the hardened moulding sands. It was found that strength of the moulding sands hardened with microwaves for 4 min is very close to that measured after traditional drying at 110 °C for 120 min. So, application of microwave hardening ensures significant shortening of the process time to the value comparable with CO2 hardening but guaranteeing over 10-fold increase of mechanical properties. Analysis of SEM images of hardened moulding sands permitted explaining differences in quality parameters of moulding sands by connecting them with structure of the created bonding bridges.

Effect of Pigment Colouring on Physico-mechanical Properties of Hardened Cement Paste and Response of Colour Intensity to UV Radiation

International Nuclear Information System (INIS)

Khattab, M.M.; Abdel-Rahman, H.A.; Hassan, M.S.

2010-01-01

In this work, different ratios of pigment colour was mixed with cement paste during mixing. The pigment colour used was Phthalocyanine Green. The effect of pigment colouring on hardened cement paste (HCP) was characterized in terms of compressive strength, IR spectroscopic analysis and X-ray diffraction. In addition, the effect of UV radiation on the colour strength of hardened cement paste/pigment colour composites was investigated. The results indicated that the increase in the ratio of pigment colour was accompanied with a slight decrease in the values of compressive strength. The exposure of the coloured hardened cement paste to UV radiation for long lengths of time causes a little effect on the colour intensity

Some aspects of the metal purity in high strength Al-alloys

International Nuclear Information System (INIS)

Banizs, K.; Csernay-Balint, J.; Voeroes, G.

1990-01-01

The effect of Fe and Si on the properties of some high strength age-hardenable Al-alloys was investigated. It was found that a certain quantity (> 0.15 %) of Fe is advantageous to the formation of the cell-structure in the cast ingot both in the AlCuMg and AlZnMgCu alloys. An increased Fe-content causes a finer cell-structure. A higher Fe:Si ratio results in more homogeneous cell size distribution. Higher Si-content in the alloy decreases the favourable cast parameter range and increases the inclination to cracking of large diameter (> 270 mm) ingots. The reason of the correlation found between metal purity and mechanical properties is discussed

Characterization of Radiation Hardened Bipolar Linear Devices for High Total Dose Missions

Science.gov (United States)

McClure, Steven S.; Harris, Richard D.; Rax, Bernard G.; Thorbourn, Dennis O.

2012-01-01

Radiation hardened linear devices are characterized for performance in combined total dose and displacement damage environments for a mission scenario with a high radiation level. Performance at low and high dose rate for both biased and unbiased conditions is compared and the impact to hardness assurance methodology is discussed.

Relationship between 0.2% proof stress and Vickers hardness of work-hardened low carbon austenitic stainless steel, 316SS

International Nuclear Information System (INIS)

Matsuoka, Saburo

2004-01-01

Stress corrosion cracking (SCC) occurs in shrouds and piping made of low carbon austenitic stainless steels at nuclear power plants. A work-hardened layer is considered to be one of the probable causes for this occurrence. The maximum Vickers hardness measured at the work-hardened layer is 400 HV. It is important to determine the yield strength and tensile strength of the work-hardened layer in the investigation on the causes of SCC. However, the tensile specimen cannot be obtained since the thickness of the work-hardened layer is as mall as several hundred μm, therefore, it is useful if we can estimate these strengths from its Vickers hardness. Consequently, we investigated the relationships between Vickers hardness versus yield strength and tensile strength using the results obtained on various steels in a series of Fatigue Data Sheets published by the National Institute for Materials Science and results newly obtained on a parent material and rolled materials (reduction of area: 10 - 50%, maximum hardness: 350 HV) for a low carbon stainless steel. The results showed that (1) the relationship between the 0.2% proof stress and the Vickers hardness can be described by a single straight line regardless of strength, structure, and rolling ratio, however, (2) the tensile strength is not correlated with the Vickers hardness, and the austenitic stainless steel in particular shows characteristics different from those of other steels. (author)

Neutron flux and annealing effects on irradiation hardening of RPV materials

Science.gov (United States)

Chaouadi, R.; Gérard, R.

2011-11-01

This paper aims to examine an eventual effect of neutron flux, sometimes referred to as dose rate effect, on irradiation hardening of a typical A533B reactor pressure vessel steel. Tensile tests on both low flux (reactor surveillance data) and high flux (BR2 reactor) were performed in a large fluence range. The obtained results indicate two features. First, the surveillance data exhibit a constant (˜90 MPa) higher yield strength than the high flux data. However, this difference cannot be explained from a flux effect but most probably from differences in the initial tensile properties. The hardening kinetic of both low and high flux is the same. Annealing at low temperature, 345 °C/40 h, to eventually reveal unstable matrix damage did not affect both BR2 and surveillance specimens. This is confirmed by other annealing experimental data including both tensile and hardness measurements and tensile data on A508 forging and weld. It is suggested that the absence of flux effect on the tensile properties while different radiation-induced microstructures can be attributed to thermal ageing effects.

Hardening Azure applications

CERN Document Server

Gaurav, Suraj

2015-01-01

Learn what it takes to build large scale, mission critical applications -hardened applications- on the Azure cloud platform. This 208 page book covers the techniques and engineering principles that every architect and developer needs to know to harden their Azure/.NET applications to ensure maximum reliability and high availability when deployed at scale. While the techniques are implemented in .NET and optimized for Azure, the principles here will also be valuable for users of other cloud-based development platforms. Applications come in a variety of forms, from simple apps that can be bui

Radiation hardened COTS-based 32-bit microprocessor

International Nuclear Information System (INIS)

Haddad, N.; Brown, R.; Cronauer, T.; Phan, H.

1999-01-01

A high performance radiation hardened 32-bit RISC microprocessor based upon a commercial single chip CPU has been developed. This paper presents the features of radiation hardened microprocessor, the methods used to radiation harden this device, the results of radiation testing, and shows that the RAD6000 is well-suited for the vast majority of space applications. (authors)

Enhanced bake-hardening response of an Al–Mg–Si–Cu alloy with Zn addition

Energy Technology Data Exchange (ETDEWEB)

Guo, M.X., E-mail: mingxingguo@skl.ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Sha, G., E-mail: gang.sha@njust.edu.cn [School of Materials Science and Engineering, Nanjing University of Science and Technology, Jiangsu 210094 (China); Cao, L.Y. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Liu, W.Q. [Key Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China); Zhang, J.S.; Zhuang, L.Z. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

2015-07-15

This study reports that Zn addition greatly enhances the bake-hardening response of an Al–Mg–Si–Cu alloy. The pre-aged alloy exhibits a high strength increment of 135 MPa after paint baking. Differential scanning calorimetry, atom probe tomography and high-resolution transmission electron microscopy reveal that Zn addition and pre-aging have significant effects on the solute nanostructure formation. Zn atoms partition into solute clusters/GP zones, and reduce the activation energy of β” precipitation in the alloy. - Highlights: • Zn addition can improve the bake-hardening response of an Al–Mg–Si–Cu alloy. • Zn addition can stabilize the solute clusters/GP zones from dissolution. • Zn addition can reduce the size of clusters formed in the pre-aging treatment. • Zn partitioned into solute clusters/GP zones and β” in the Zn-containing Al alloy.

The Science of Cost-Effective Materials Design - A Study in the Development of a High Strength, Impact Resistant Steel

Science.gov (United States)

Abrahams, Rachel

2017-06-01

Intermediate alloy steels are widely used in applications where both high strength and toughness are required for extreme/dynamic loading environments. Steels containing greater than 10% Ni-Co-Mo are amongst the highest strength martensitic steels, due to their high levels of solution strengthening, and preservation of toughness through nano-scaled secondary hardening, semi-coherent hcp-M2 C carbides. While these steels have high yield strengths (σy 0.2 % >1200 MPa) with high impact toughness values (CVN@-40 >30J), they are often cost-prohibitive due to the material and processing cost of nickel and cobalt. Early stage-I steels such as ES-1 (Eglin Steel) were developed in response to the high cost of nickel-cobalt steels and performed well in extreme shock environments due to the presence of analogous nano-scaled hcp-Fe2.4 C epsilon carbides. Unfortunately, the persistence of W-bearing carbides limited the use of ES-1 to relatively thin sections. In this study, we discuss the background and accelerated development cycle of AF96, an alternative Cr-Mo-Ni-Si stage-I temper steel using low-cost heuristic and Integrated Computational Materials Engineering (ICME)-assisted methods. The microstructure of AF96 was tailored to mimic that of ES-1, while reducing stability of detrimental phases and improving ease of processing in industrial environments. AF96 is amenable to casting and forging, deeply hardenable, and scalable to 100,000 kg melt quantities. When produced at the industrial scale, it was found that AF96 exhibits near-statistically identical mechanical properties to ES-1 at 50% of the cost.

Rapid hardening induced by electric pulse annealing in nanostructured pure aluminum

DEFF Research Database (Denmark)

Zeng, Wei; Shen, Yao; Zhang, Ning

2012-01-01

Nanostructured pure aluminum was fabricated by heavy cold-rolling and then subjected to recovery annealing either by applying electric pulse annealing or by traditional air furnace annealing. Both annealing treatments resulted in an increase in yield strength due to the occurrence of a “dislocation...... source-limited hardening” mechanism. However, the hardening kinetics was substantially faster for the electric pulse annealed material. Detailed microstructural characterization suggested that the rapid hardening during electric pulse annealing is related to an enhanced rate of recovery of dislocation...

High temperature, radiation hardened electronics for application to nuclear power plants

International Nuclear Information System (INIS)

Gover, J.E.

1980-01-01

Electronic circuits were developed and built at Sandia for many aerospace and energy systems applications. Among recent developments were high temperature electronics for geothermal well logging and radiation hardened electronics for a variety of aerospace applications. Sandia has also been active in technology transfer to commercial industry in both of these areas

High Early-Age Strength Concrete for Rapid Repair

Science.gov (United States)

Maler, Matthew O.

The aim of this research was to identify High Early-Age Strength (HES) concrete batch designs, and evaluate their suitability for use in the rapid repair of highways and bridge decks. To this end, two criteria needed to be met; a minimum compressive strength of 20.68 MPa (3000 psi) in no later than 12 hours, and a drying shrinkage of less than 0.06 % at 28 days after curing. The evaluations included both air-entrained, and non-air-entrained concretes. The cement types chosen for this study included Type III and Type V Portland cement and "Rapid Set"--a Calcium Sulfoaluminate (CSA) cement. In addition, two blended concretes containing different ratios of Type V Portland cement and CSA cement were investigated. The evaluation of the studied concretes included mechanical properties and transport properties. Additionally, dimensional stability and durability were investigated. Evaluations were conducted based on cement type and common cement factor. Fresh property tests showed that in order to provide a comparable workability, and still remain within manufactures guideline for plasticizer, the water-to-cement ratio was adjusted for each type of cement utilized. This resulted in the need to increase the water-to-cement ratio as the Blaine Fineness of the cement type increased (0.275 for Type V Portland cement, 0.35 for Type III Portland cement, and 0.4 for Rapid Set cement). It was also observed that negligible changes in setting time occurred with increasing cement content, whereas changes in cement type produced notable differences. The addition of air-entrainment had beneficial effect on workability for the lower cement factors. Increasing trends for peak hydration heat were seen with increases in cement factor, cement Blaine Fineness, and accelerator dosage. Evaluation of hardened properties revealed opening times as low as 5 hours for Type V Portland cement with 2.0 % accelerator per cement weight and further reduction in opening time by an hour when accelerator

Study of radiation hardening in reactor pressure vessel steels

International Nuclear Information System (INIS)

Nogiwa, Kimihiro; Nishimura, Akihiko

2008-01-01

In order to investigate the dependence of hardening on copper precipitate diameter and density, in-situ transmission electron microscopy (TEM) observations during tensile tests of dislocation gliding through copper rich-precipitates in thermally aged and neutron irradiated Fe-Cu alloys were performed. The obstacle strength has been estimated from the critical bow-out angle, φ, of dislocations. The obstacle distance on the dislocation line measured from in-situ TEM observations were compared with number density and diameter measured by 3D-AP (three dimensional atom probe) and TEM observation. A comparison is made between hardening estimation based on the critical bowing angles and those obtained from conventional tensile tests. (author)

Mechanical characteristics of hardened concrete with different mineral admixtures: a review.

Science.gov (United States)

Ayub, Tehmina; Khan, Sadaqat Ullah; Memon, Fareed Ahmed

2014-01-01

The available literature identifies that the addition of mineral admixture as partial replacement of cement improves the microstructure of the concrete (i.e., porosity and pore size distribution) as well as increasing the mechanical characteristics such as drying shrinkage and creep, compressive strength, tensile strength, flexural strength, and modulus of elasticity; however, no single document is available in which review and comparison of the influence of the addition of these mineral admixtures on the mechanical characteristics of the hardened pozzolanic concretes are presented. In this paper, based on the reported results in the literature, mechanical characteristics of hardened concrete partially containing mineral admixtures including fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK), and rice husk ash (RHA) are discussed and it is concluded that the content and particle size of mineral admixture are the parameters which significantly influence the mechanical properties of concrete. All mineral admixtures enhance the mechanical properties of concrete except FA and GGBS which do not show a significant effect on the strength of concrete at 28 days; however, gain in strength at later ages is considerable. Moreover, the comparison of the mechanical characteristics of different pozzolanic concretes suggests that RHA and SF are competitive.

Role of work hardening characteristics of matrix alloys in the ...

Indian Academy of Sciences (India)

Unknown

with increasing prismatic punching of dislocations in the order 7075, 2014, 7010, 2024, 6061 and commercial purity aluminium leading to increased strength increments is noted. Keywords. Metal matrix composites; strengthening; work hardening rate; dislocation density. 1. Introduction. While in continuous fibre composites, ...

Contributions of Cu-rich clusters, dislocation loops and nanovoids to the irradiation-induced hardening of Cu-bearing low-Ni reactor pressure vessel steels

Energy Technology Data Exchange (ETDEWEB)

Bergner, F., E-mail: f.bergner@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany); Gillemot, F. [Centre for Energy Research of the Hungarian Academy of Sciences, 29-33 Konkoly-Thege street, 1121 Budapest XII (Hungary); Hernández-Mayoral, M.; Serrano, M. [Division of Materials, CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain); Török, G. [Wigner Research Center for Physics of the Hungarian Academy of Sciences, 29-33 Konkoly-Thege street, 1121 Budapest XII (Hungary); Ulbricht, A.; Altstadt, E. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany)

2015-06-15

Highlights: • TEM and SANS were applied to estimate mean size and number density of loops, nanovoids and Cu-rich clusters. • A three-feature dispersed-barrier hardening model was applied to estimate the yield stress increase. • The values and errors of the dimensionless obstacle strength were estimated in a consistent way. • Nanovoids are stronger obstacles for dislocation glide than dislocation loops, loops are stronger than Cu-rich clusters. • For reactor-relevant conditions, Cu-rich clusters contribute most to hardening due to their high number density. - Abstract: Dislocation loops, nanovoids and Cu-rich clusters (CRPs) are known to represent obstacles for dislocation glide in neutron-irradiated reactor pressure vessel (RPV) steels, but a consistent experimental determination of the respective obstacle strengths is still missing. A set of Cu-bearing low-Ni RPV steels and model alloys was characterized by means of SANS and TEM in order to specify mean size and number density of loops, nanovoids and CRPs. The obstacle strengths of these families were estimated by solving an over-determined set of linear equations. We have found that nanovoids are stronger than loops and loops are stronger than CRPs. Nevertheless, CRPs contribute most to irradiation hardening because of their high number density. Nanovoids were only observed for neutron fluences beyond typical end-of-life conditions of RPVs. The estimates of the obstacle strength are critically compared with reported literature data.

The maximum percentage of fly ash to replace part of original Portland cement (OPC) in producing high strength concrete

Science.gov (United States)

Mallisa, Harun; Turuallo, Gidion

2017-11-01

This research investigates the maximum percent of fly ash to replace part of Orginal Portland Cement (OPC) in producing high strength concrete. Many researchers have found that the incorporation of industrial by-products such as fly ash as in producing concrete can improve properties in both fresh and hardened state of concrete. The water-binder ratio was used 0.30. The used sand was medium sand with the maximum size of coarse aggregate was 20 mm. The cement was Type I, which was Bosowa Cement produced by PT Bosowa. The percentages of fly ash to the total of a binder, which were used in this research, were 0, 10, 15, 20, 25 and 30%; while the super platicizer used was typed Naptha 511P. The results showed that the replacement cement up to 25 % of the total weight of binder resulted compressive strength higher than the minimum strength at one day of high-strength concrete.

Correlation Between Microstructure and Low-Temperature Impact Toughness of Simulated Reheated Zones in the Multi-pass Weld Metal of High-Strength Steel

Science.gov (United States)

Kang, Yongjoon; Park, Gitae; Jeong, Seonghoon; Lee, Changhee

2018-01-01

A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the mechanical properties (especially toughness) of welded structures. In this study, the low-temperature toughness of the simulated reheated zone in multi-pass weld metal was evaluated and compared to that of the as-deposited zone using microstructural analyses. Two kinds of high-strength steel welds with different hardenabilities were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to peak temperatures above Ac3 using a Gleeble simulator. When the weld metals were reheated, their toughness deteriorated in response to the increase in the fraction of detrimental microstructural components, i.e., grain boundary ferrite and coalesced bainite in the weld metals with low and high hardenabilities, respectively. In addition, toughness deterioration occurred in conjunction with an increase in the effective grain size, which was attributed to the decrease in nucleation probability of acicular ferrite; the main cause for this decrease changed depending on the hardenability of the weld metal.

Mechanical Characteristic of Remanufacturing of FV520B Precipitation Hardening Stainless Steel Using MAG Surfacing Deposition

Directory of Open Access Journals (Sweden)

LIU Jian

2017-10-01

Full Text Available Surfacing deposition forming method was adopted to carry out remanufacturing experiment of FV520B precipitation hardening stainless steel. Then the mechanical property characteristic of the remanufacturing layer was tested and studied, contrasted with the corresponding property of substrate. The results show that the remanufacturing layer, formed with MAG surfacing of FV520B precipitation hardening stainless steel has mechanical characteristic with high strength and hardness, the tensile strength reaches 1195MPa, exceeds 1092MPa of substrate, yield strength is 776MPa and average hardness is 336HV, is close to the corresponding property of substrate which is 859MPa and 353HV respectively; however, the elongation and impact toughness of the remanufacturing layer is merely 8.92% and 61J/cm2 respectively, it has a large gap with the corresponding property 19.72% and 144J/cm2 respectively of substrate. Fracture and microstructure analysis on specimens shows that the microstructure of remanufacturing layer is fast cooling non-equilibrium crystallized lath martensite, and carbide precipitated strengthening phase such as NbC, MoC, M23C6,etc, which is the reason that remanufacturing layer has high strength and high hardness. But as lack of aging treatment and Cu strengthening phase, and the weak interface between contaminating brittle phase or large size spherical particles and substrate will deteriorate the deformability and induce stress concentration and cracking when the material is load-carrying, and is the main reason of the remanufacturing layer having lower static tensile elongation and impact toughness.

Effect of hardening on the crack growth rate of austenitic stainless steels in primary PWR conditions

International Nuclear Information System (INIS)

Castano, M.L.; Garcia, M.S.; Diego, G. de; Gomez-Briceno, D.; Francia, L.

2002-01-01

Intergranular cracking of non-sensitized materials, found in light water reactor (LWR) components exposed to neutron radiation, has been attributed to Irradiation Assisted Stress Corrosion Cracking (IASCC). Cracking of baffle former bolts, fabricated of AISI-316L and AISI-347, have been reported in some Europeans and US PWR plants. Examinations of removed bolts indicate the intergranular cracking characteristics can be associated with IASCC phenomena. Neutron radiation produce critical modifications of the microstructure and microchemical of stainless steels such hardening due to irradiation and Radiation Induce Segregation (RIS) at grain boundaries, among others. Chromium depletion at grain boundary due to RIS seems to justify the intergranular cracking of irradiated materials, both in plant and in lab tests, at high electrochemical corrosion potential (BWR-NWC environments), but it is not enough to explain cracking at low corrosion potential (BWR-HWC and PWR environments). In these latter conditions, hardening is considered a possible additional mechanism to explain the behavior of irradiated material. Radiation Hardening can be simulated in non irradiated material by mechanical deformation. Although some differences exists in the types of defects produced by radiation and mechanical deformation, it is accepted that the study of the stress corrosion behavior of unirradiated austenitic steels with different hardening levels would contribute to the understanding of IASCC mechanism. In order to evaluate the influence of hardening on the stress corrosion susceptibility of austenitic steels, crack growth rate tests with 316L and 347 stainless steels with nominal yield strengths from 500 to 900 MPa, produced by cold work are being carried out at 340 deg C in PWR conditions. Preliminary results indicate that crack propagation was obtained in the 316Lss and 347ss cold worked, even with a yield strength of 550 MPa. (authors)

Simultaneous surface engineering and bulk hardening of precipitation hardening stainless steel

DEFF Research Database (Denmark)

Frandsen, Rasmus Berg; Christiansen, Thomas; Somers, Marcel A. J.

2006-01-01

This article addresses simultaneous bulk precipitation hardening and low temperature surface engineering of two commercial precipitation hardening stainless steels: Sandvik Nanoflex® and Uddeholm Corrax®. Surface engineering comprised gaseous nitriding or gaseous carburising. Microstructural....... The duration and temperature of the nitriding/carburising surface hardening treatment can be chosen in agreement with the thermal treatment for obtaining optimal bulk hardness in the precipitation hardening stainless steel....... characterisation of the cases developed included X-ray diffraction analysis, reflected light microscopy and micro-hardness testing. It was found that the incorporation of nitrogen or carbon resulted in a hardened case consisting of a combination of (tetragonal) martensite and expanded (cubic) austenite...

On the Effect of Natural Aging Prior to Low Temperature ECAP of a High-Strength Aluminum Alloy

Directory of Open Access Journals (Sweden)

Sebastian Fritsch

2018-01-01

Full Text Available Severe plastic deformation (SPD can be used to generate ultra-fine grained microstructures and thus to increase the strength of many materials. Unfortunately, high strength aluminum alloys are generally hard to deform, which puts severe limits on the feasibility of conventional SPD methods. In this study, we use low temperature equal-channel angular pressing (ECAP to deform an AA7075 alloy. We perform ECAP in a custom-built, cooled ECAP-tool with an internal angle of 90° at −60 °C and with an applied backpressure. In previous studies, high-strength age hardening aluminum alloys were deformed in a solid solution heat treated condition to improve the mechanical properties in combination with subsequent (post-ECAP aging. In the present study, we systematically vary the initial microstructure—i.e., the material condition prior to low temperature ECAP—by (pre-ECAP natural aging. The key result of the present study is that precipitates introduced prior to ECAP speed up grain refinement during ECAP. Longer aging times lead to accelerated microstructural evolution, to increasing strength, and to a transition in fracture behavior after a single pass of low temperature ECAP. These results demonstrate the potential of these thermo-mechanical treatments to produce improved properties of high-strength aluminum alloys.

Utilization of Local Ingredients for the Production of High-Early-Strength Engineered Cementitious Composites

Directory of Open Access Journals (Sweden)

Hanwen Deng

2018-01-01

Full Text Available The rapid repair and retrofitting of existing transportation infrastructure requires dimensional stability and ductile repair material that can obtain sufficiently high strength in a few hours to accommodate the large loading and deformation at an early age. Engineering cementitious composites (ECCs is a class representative of the new generation of high-performance fiber-reinforced cement-based composites (HPFRCC with medium fiber content. The unique properties of tremendous ductility and tight multiple crack behavior indicate that ECC can be used as an effective retrofit material. The wide application of this material in China will require the use of all local ingredients. In this study, based on Chinese domestic ingredients, including matrix materials and all fibers, high-early-strength ECC (HES-ECC was designed under the guidance of strain-hardening criterion of ECC. The matrix properties and fiber/matrix interfacial micromechanics properties were obtained from three-point-bending test and single-fiber pullout test. The mechanical properties of HES-ECC were achieved by direct tensile test. The experimental results show that HES-ECC was successfully developed by using all Chinese materials. When using the domestic PVA fiber at 2%, the strength requirement can be achieved but only a low ductility. When using the domestic PE fiber at 0.8%, the strength and deformation requirement both can be obtained. The HES-ECC developed in this study exhibited compressive strength of more than 25 MPa within 6 hours, and an ultimate tensile strength of 5-6 MPa and tensile strain capacity of 3-4% after 60 days. Moreover, the cost of using domestic fiber can be largely reduced compared with using imported fiber, up to 70%; it is beneficial to the promotion of these high-early-strength ECCs in the Chinese market.

Effects of cooling rate, austenitizing temperature and austenite deformation on the transformation behavior of high-strength boron steel

International Nuclear Information System (INIS)

Mun, Dong Jun; Shin, Eun Joo; Choi, Young Won; Lee, Jae Sang; Koo, Yang Mo

2012-01-01

Highlights: ► Non-equilibrium segregation of B in steel depends strongly on the cooling rate. ► A higher austenitization temperature reduced the B hardenability effect. ► An increase in B concentration at γ grain boundaries accelerates the B precipitation. ► The loss of B hardenability effect is due to intragranular borocarbide precipitation. ► The controlled cooling after hot deformation increased the B hardenability effect. - Abstract: The phase transformation behavior of high-strength boron steel was studied considering the segregation and precipitation behavior of boron (B). The effects of cooling rate, austenitizing temperature and austenite deformation on the transformation behavior of B-bearing steel as compared with B-free steel were investigated by using dilatometry, microstructural observations and analysis of B distribution. The effects of these variables on hardenability were discussed in terms of non-equilibrium segregation mechanism and precipitation behavior of B. The retardation of austenite-to-ferrite transformation by B addition depends strongly on cooling rate (CR); this is mainly due to the phenomenon of non-equilibrium grain boundary segregation of B. The hardenability effect of B-bearing steel decreased at higher austenitizing temperature due to the precipitation of borocarbide along austenite grain boundaries. Analysis of B distribution by second ion mass spectroscopy confirmed that the grain boundary segregation of B occurred at low austenitizing temperature of 900 °C, whereas B precipitates were observed along austenite grain boundaries at high austenitizing temperature of 1200 °C. The significant increase in B concentration at austenite grain boundaries due to grain coarsening and a non-equilibrium segregation mechanism may lead to the B precipitation. In contrast, solute B segregated to austenite grain boundaries during cooling after heavy deformation became more stable because the increase in boundary area by grain

Age hardening of cold-worked Zr-2.5 wt% Nb pressure tube alloy

International Nuclear Information System (INIS)

Kishore, R.; Singh, R.N.; Dey, G.K.; Sinha, T.K.

1992-01-01

Specimens for hardness and tensile tests, machined from a cold-worked zirconium-2.5% niobium pressure tube, with their axes parallel to longitudinal and transverse directions, were aged for 1 hr. at 300-500 C. The age hardening behaviour was monitored by mechanical tests, electron-microscopy and x-ray diffraction. In addition a few studies were carried on longitudinal tension specimens subjected to prolonged ageing (100-1000 hrs) at 300 C. It was observed that the short-term (1 hour) thermal ageing of this material at 300-400 C caused an increase in both strength and hardness without affecting ductility. It appears that the observed age-hardening is due to precipitation hardening by a niobium-rich phase and softening by recovery of cold-work and that the phenomenon is influenced by crystallographic texture. Further it was noted that a prolonged ageing at 300 C upto 1000 hrs, did not cause any appreciable changes in strength and ductility of the material compared to those obtained by 1 hour ageing at the same temperature. (author). 11 refs., 3 figs., 2 tabs

STRENGTH OF NANOMODIFIED HIGH-STRENGTH LIGHTWEIGHT CONCRETES

Directory of Open Access Journals (Sweden)

NOZEMTСEV Alexandr Sergeevich

2013-02-01

Full Text Available The paper presents the results of research aimed at development of nanomodified high-strength lightweight concrete for construction. The developed concretes are of low average density and high ultimate compressive strength. It is shown that to produce this type of concrete one need to use hollow glass and aluminosilicate microspheres. To increase the durability of adhesion between cement stone and fine filler the authors offer to use complex nanodimensinal modifier based on iron hydroxide sol and silica sol as a surface nanomodifier for hollow microspheres. It is hypothesized that the proposed modifier has complex effect on the activity of the cement hydration and, at the same time increases bond strength between filler and cement-mineral matrix. The compositions for energy-efficient nanomodified high-strength lightweight concrete which density is 1300…1500 kg/m³ and compressive strength is 40…65 MPa have been developed. The approaches to the design of high-strength lightweight concrete with density of less than 2000 kg/m³ are formulated. It is noted that the proposed concretes possess dense homogeneous structure and moderate mobility. Thus, they allow processing by vibration during production. The economic and practical implications for realization of high-strength lightweight concrete in industrial production have been justified.

Accurate hardening modeling as basis for the realistic simulation of sheet forming processes with complex strain-path changes

International Nuclear Information System (INIS)

Levkovitch, Vladislav; Svendsen, Bob

2007-01-01

Sheet metal forming involves large strains and severe strain-path changes. Large plastic strains lead in many metals to the development of persistent dislocation structures resulting in strong flow anisotropy. This induced anisotropic behavior manifests itself in the case of a strain path change through very different stress-strain responses depending on the type of the strain-path change. While many metals exhibit a drop of the yield stress (Bauschinger effect) after a load reversal, some metals show an increase of the yield stress after an orthogonal strain-path change (so-called cross hardening). To model the Bauschinger effect, kinematic hardening has been successfully used for years. However, the usage of the kinematic hardening leads automatically to a drop of the yield stress after an orthogonal strain-path change contradicting tests exhibiting the cross hardening effect. Another effect, not accounted for in the classical elasto-plasticity, is the difference between the tensile and compressive strength, exhibited e.g. by some steel materials. In this work we present a phenomenological material model whose structure is motivated by polycrystalline modeling that takes into account the evolution of polarized dislocation structures on the grain level - the main cause of the induced flow anisotropy on the macroscopic level. The model considers besides the movement of the yield surface and its proportional expansion, as it is the case in conventional plasticity, also the changes of the yield surface shape (distortional hardening) and accounts for the pressure dependence of the flow stress. All these additional attributes turn out to be essential to model the stress-strain response of dual phase high strength steels subjected to non-proportional loading

Accurate Hardening Modeling As Basis For The Realistic Simulation Of Sheet Forming Processes With Complex Strain-Path Changes

International Nuclear Information System (INIS)

Levkovitch, Vladislav; Svendsen, Bob

2007-01-01

Sheet metal forming involves large strains and severe strain-path changes. Large plastic strains lead in many metals to the development of persistent dislocation structures resulting in strong flow anisotropy. This induced anisotropic behavior manifests itself in the case of a strain path change through very different stress-strain responses depending on the type of the strain-path change. While many metals exhibit a drop of the yield stress (Bauschinger effect) after a load reversal, some metals show an increase of the yield stress after an orthogonal strain-path change (so-called cross hardening). To model the Bauschinger effect, kinematic hardening has been successfully used for years. However, the usage of the kinematic hardening leads automatically to a drop of the yield stress after an orthogonal strain-path change contradicting tests exhibiting the cross hardening effect. Another effect, not accounted for in the classical elasto-plasticity, is the difference between the tensile and compressive strength, exhibited e.g. by some steel materials. In this work we present a phenomenological material model whose structure is motivated by polycrystalline modeling that takes into account the evolution of polarized dislocation structures on the grain level - the main cause of the induced flow anisotropy on the macroscopic level. The model considers besides the movement of the yield surface and its proportional expansion, as it is the case in conventional plasticity, also the changes of the yield surface shape (distortional hardening) and accounts for the pressure dependence of the flow stress. All these additional attributes turn out to be essential to model the stress-strain response of dual phase high strength steels subjected to non-proportional loading

Effect of Slag Content and Hardening Accelerator Dosage on the Physico Mechanical Properties of Cement and Concrete

International Nuclear Information System (INIS)

Derabla, R.; Mokrani, I.; Benmalek, M.L.

2011-01-01

Our contribution consists at the study of the effect of (0 %, 0.2 % and 0.34 %) dosage of an hardening accelerating plasticizer (Plastocrete 160, produced by Sika Aldjazair) on the properties of normal mortar and concretes prepared with portland cement artificial of Hadjar Soud cement factory (Skikda - Algeria) with addition of (10 % and 20 %) of granulated blast furnace slag finely crushed of the El Hadjar blast furnace (Annaba - Algeria). The tests are focused to the physical and mechanical characteristics of elaborated materials to knowing: setting time, porosity, water absorption capacity and the test of compressive strength at 2, 7 and 28 days. The results obtained show clearly the reliability of the additive used to accelerate the hardening and to obtain high strengths at early age, which increase by increasing of the additive dosage. For the slag, its low hydraulic capacity does not make it profitable than at the long term (beyond 28 days). (author)

A hardenability test proposal

Energy Technology Data Exchange (ETDEWEB)

Murthy, N.V.S.N. [Ingersoll-Rand (I) Ltd., Bangalore (India)

1996-12-31

A new approach for hardenability evaluation and its application to heat treatable steels will be discussed. This will include an overview and deficiencies of the current methods and discussion on the necessity for a new approach. Hardenability terminology will be expanded to avoid ambiguity and over-simplification as encountered with the current system. A new hardenability definition is proposed. Hardenability specification methods are simplified and rationalized. The new hardenability evaluation system proposed here utilizes a test specimen with varying diameter as an alternative to the cylindrical Jominy hardenability test specimen and is readily applicable to the evaluation of a wide variety of steels with different cross-section sizes.

Literature survey on phase composition of hardened cement paste containing fly ash

International Nuclear Information System (INIS)

Otsuka, Taku; Yamamoto, Takeshi

2015-01-01

The purpose of this literature survey is to collect the knowledge on the effect of fly ash in hardened cement paste and the information about evaluation of physicochemical performance based on phase composition of hardened cement paste. The performance of hardened cement paste containing fly ash is affected by the property of fly ash, hydration of cement and pozzolanic reaction of fly ash. Some properties of fly ash such as density and chemical composition are reflected in phase composition, showing the progress of cement hydration and pozzolanic reaction. Therefore clarification of the relationship of phase composition and performance will lead to appropriate evaluation of the property of fly ash. The amount of pore, chemical shrinkage, pore solution, compressive strength, Young modulus and alkali silica reaction have relations to the phase composition of hardened cement paste. It is considered as future subject to clarify the relationship of phase composition and performance for various properties of fly ash. (author)

High-Tensile Strength Tape Versus High-Tensile Strength Suture: A Biomechanical Study.

Science.gov (United States)

Gnandt, Ryan J; Smith, Jennifer L; Nguyen-Ta, Kim; McDonald, Lucas; LeClere, Lance E

2016-02-01

To determine which suture design, high-tensile strength tape or high-tensile strength suture, performed better at securing human tissue across 4 selected suture techniques commonly used in tendinous repair, by comparing the total load at failure measured during a fixed-rate longitudinal single load to failure using a biomechanical testing machine. Matched sets of tendon specimens with bony attachments were dissected from 15 human cadaveric lower extremities in a manner allowing for direct comparison testing. With the use of selected techniques (simple Mason-Allen in the patellar tendon specimens, whip stitch in the quadriceps tendon specimens, and Krackow stitch in the Achilles tendon specimens), 1 sample of each set was sutured with a 2-mm braided, nonabsorbable, high-tensile strength tape and the other with a No. 2 braided, nonabsorbable, high-tensile strength suture. A total of 120 specimens were tested. Each model was loaded to failure at a fixed longitudinal traction rate of 100 mm/min. The maximum load and failure method were recorded. In the whip stitch and the Krackow-stitch models, the high-tensile strength tape had a significantly greater mean load at failure with a difference of 181 N (P = .001) and 94 N (P = .015) respectively. No significant difference was found in the Mason-Allen and simple stitch models. Pull-through remained the most common method of failure at an overall rate of 56.7% (suture = 55%; tape = 58.3%). In biomechanical testing during a single load to failure, high-tensile strength tape performs more favorably than high-tensile strength suture, with a greater mean load to failure, in both the whip- and Krackow-stitch models. Although suture pull-through remains the most common method of failure, high-tensile strength tape requires a significantly greater load to pull-through in a whip-stitch and Krakow-stitch model. The biomechanical data obtained in the current study indicates that high-tensile strength tape may provide better repair

Burst strength of tubing and casing based on twin shear unified strength theory.

Science.gov (United States)

Lin, Yuanhua; Deng, Kuanhai; Sun, Yongxing; Zeng, Dezhi; Liu, Wanying; Kong, Xiangwei; Singh, Ambrish

2014-01-01

The internal pressure strength of tubing and casing often cannot satisfy the design requirements in high pressure, high temperature and high H2S gas wells. Also, the practical safety coefficient of some wells is lower than the design standard according to the current API 5C3 standard, which brings some perplexity to the design. The ISO 10400: 2007 provides the model which can calculate the burst strength of tubing and casing better than API 5C3 standard, but the calculation accuracy is not desirable because about 50 percent predictive values are remarkably higher than real burst values. So, for the sake of improving strength design of tubing and casing, this paper deduces the plastic limit pressure of tubing and casing under internal pressure by applying the twin shear unified strength theory. According to the research of the influence rule of yield-to-tensile strength ratio and mechanical properties on the burst strength of tubing and casing, the more precise calculation model of tubing-casing's burst strength has been established with material hardening and intermediate principal stress. Numerical and experimental comparisons show that the new burst strength model is much closer to the real burst values than that of other models. The research results provide an important reference to optimize the tubing and casing design of deep and ultra-deep wells.

Observation of a New Mechanism Balancing Hardening and Softening in Metals

DEFF Research Database (Denmark)

Yu, Tianbo; Hansen, Niels; Huang, Xiaoxu

2014-01-01

Plastic deformation of metals refines the microstructure and increases the strength through work hardening, but this effect of deformation is counterbalanced by dynamic recovery. After large strain, the microstructure typically shows a lamellar morphology, with finely spaced lamellar boundaries...... connected by triple junctions. Here, we report that mechanically assisted triple junction motion is an important contributor to dynamic recovery, leading to an almost steady state. Triple junction motion replaces two boundaries by one, while maintaining the structural morphology. The observation...... rationalizes both a decreasing work hardening rate and the approach to a dynamic equilibrium of structural refinement at large strains....

A new high-strength iron base austenitic alloy with good toughness and corrosion resistance (GE-EPRI alloy-TTL)

International Nuclear Information System (INIS)

Ganesh, S.

1989-01-01

A new high strength, iron based, austenitic alloy has been successfully developed by GE-EPRI to satisfy the strength and corrosion resistance requirements of large retaining rings for high capacity generators (>840Mw). This new alloy is a modified version of the EPRI alloy-T developed by the University of California, Berkeley, in an earlier EPRI program. It is age hardenable and has the nominal composition (weight %): 34.5 Ni, 5Cr, 3Ti, 1Nb, 1Ta, 1Mo, .5Al, .3V, .01B. This composition was selected based on detailed metallurgical and processing studies on modified versions of alloy-T. These studies helped establish the optimum processing conditions for the new alloy and enabled the successful scale-up production of three large (50-52 inch dia) test rings from a 5,000 lb VIM-VAR billet. The rings were metallurgically sound and exhibited yield strength capabilities in the range 145 to 220 ksi depending on the extent of hot/cold work induced. The test rings met or exceeded all the property goals. The above alloy can provide a good combination of strength, toughness and corrosion resistance and, through an suitable modification of chemistry or processing conditions, could be a viable candidate for high strength LWR internal applications. 3 figs

Radiation-hardenable diluents for radiation-hardenable compositions

International Nuclear Information System (INIS)

Schuster, K.E.; Rosenkranz, H.J.; Furh, K.; Ruedolph, H.

1979-01-01

Radiation-crosslinkable diluents for radiation-hardenable compositions (binders) consisting of a mixture of triacrylates of a reaction product of trimethylol propane and ethylene oxide with an average degree of ethoxylation of from 2.5 to 4 are described. The ethoxylated trimethylol propane is substantially free from trimethylol propane and has the following distribution: 4 to 5% by weight of monoethoxylation product, 14 to 16% by weight of diethoxylation product, 20 to 30% by weight of triethoxylation product, 20 to 30% by weight of tetraethoxylation product, 16 to 18% by weight of pentaethoxylation product, and 6 to 8% by weight of hexaethoxylation product. The diluents effectively reduce the viscosity of radiation-hardenable compositions and do not have any adverse effect upon their reactivity or upon the properties of the resulting hardened products

Effect of water absorption by the aggregate on properties of high-strength lightweight concrete

Energy Technology Data Exchange (ETDEWEB)

Punkki, J

1996-12-31

Recently, high-strength lightweight concrete has become an interesting building material for the offshore oil industry. This doctoral thesis presents an experimental investigation of the effect of water absorption by three different types of lightweight aggregates. One type did not show any water absorption ability at all and so represented no problem to the concrete production. For the two other high-strength aggregates, which were of more conventional types, the water absorption depended not only on the properties of the aggregates, but also on the concrete mixing procedure and the properties of the fresh cement paste. When water absorbing lightweight aggregate was used in a dry condition, the workability of the concrete was significantly reduced by the water absorption of the aggregate. This effect was not present when prewetted aggregate was used. The water absorption by the lightweight aggregate also affected the early compressive strength of concrete. After one day, dry aggregate gave on the average 10 MPa higher compressive strength than did prewetted aggregate. The strength-density ratio was affected by the moisture condition of the aggregate. Dry lightweight aggregate gave 9 MPa higher compressive strength at a density of 2000 kg/m{sup 3} compared to that of prewetted aggregate. The water absorption by the lightweight also affected the microstructure of the hardened concrete. Dry lightweight aggregate gave a slightly better microstructure than normal weight aggregate. The results indicate that the use of prewetted aggregate adversely affected the transition zone between the aggregate and the cement paste. 69 refs., 58 figs., 42 tabs.

Effect of water absorption by the aggregate on properties of high-strength lightweight concrete

Energy Technology Data Exchange (ETDEWEB)

Punkki, J.

1995-12-31

Recently, high-strength lightweight concrete has become an interesting building material for the offshore oil industry. This doctoral thesis presents an experimental investigation of the effect of water absorption by three different types of lightweight aggregates. One type did not show any water absorption ability at all and so represented no problem to the concrete production. For the two other high-strength aggregates, which were of more conventional types, the water absorption depended not only on the properties of the aggregates, but also on the concrete mixing procedure and the properties of the fresh cement paste. When water absorbing lightweight aggregate was used in a dry condition, the workability of the concrete was significantly reduced by the water absorption of the aggregate. This effect was not present when prewetted aggregate was used. The water absorption by the lightweight aggregate also affected the early compressive strength of concrete. After one day, dry aggregate gave on the average 10 MPa higher compressive strength than did prewetted aggregate. The strength-density ratio was affected by the moisture condition of the aggregate. Dry lightweight aggregate gave 9 MPa higher compressive strength at a density of 2000 kg/m{sup 3} compared to that of prewetted aggregate. The water absorption by the lightweight also affected the microstructure of the hardened concrete. Dry lightweight aggregate gave a slightly better microstructure than normal weight aggregate. The results indicate that the use of prewetted aggregate adversely affected the transition zone between the aggregate and the cement paste. 69 refs., 58 figs., 42 tabs.

Development of Test Method for Simple Shear and Prediction of Hardening Behavior Considering the Branchings Effect

International Nuclear Information System (INIS)

Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo

2013-01-01

In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments

Development of Test Method for Simple Shear and Prediction of Hardening Behavior Considering the Branchings Effect

Energy Technology Data Exchange (ETDEWEB)

Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo [Sogang Univ., Seoul (Korea, Republic of)

2013-10-15

In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.

Embrittlement of irradiated ferritic/martensitic steels in the absence of irradiation hardening

Energy Technology Data Exchange (ETDEWEB)

Klueh, R.L. [Oak Ridge Noational Laboratory, TN (United States); Shiba, K. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Sokolov, M. [Oak Ridge National Laboratory, Materials Science and Technology Div., TN (United States)

2007-07-01

Full text of publication follows: Neutron irradiation of 9-12% Cr ferritic/martensitic steels below 425-450 deg. C produces microstructural defects that cause an increase in yield stress and ultimate tensile strength. This irradiation hardening causes embrittlement, which is observed in Charpy impact and toughness tests as an increase in ductile-brittle transition temperature (DBTT). Based on observations that show little change in strength in these steels irradiated above 425-450 deg. C, the general conclusion has been that no embrittlement occurs above this irradiation-hardening temperature regime. In a recent study of F82H steel irradiated at 300, 380, and 500 deg. C, irradiation hardening-an increase in yield stress-was observed in tensile specimens irradiated at the two lower temperatures, but no change was observed for the specimens irradiated at 500 deg. C. As expected, an increase in DBTT occurred for the Charpy specimens irradiated at 300 and 380 deg. C. However, there was an unexpected increase in the DBTT of the specimens irradiated at 500 deg. C. The observed embrittlement was attributed to the irradiation-accelerated precipitation of Laves phase. This conclusion was based on results from a detailed thermal aging study of F82H, in which tensile and Charpy specimens were aged at 500, 550, 600, and 650 deg. C to 30,000 h. These studies indicated that there was a decrease in yield stress at the two highest temperatures and essentially no change at the two lowest temperatures. Despite the strength decrease or no change, the DBTT increased for Charpy specimens irradiated at all four temperatures. Precipitates were extracted from thermally aged specimens, and the amount of precipitate was correlated with the increase in transition temperature. Laves phase was identified in the extracted precipitates by X-ray diffraction. Earlier studies on conventional elevated-temperature steels also showed embrittlement effects above the irradiation-hardening temperature

Influence of laser hardening with weld penetration onto mechanical and fatigue properties of 40H steel

International Nuclear Information System (INIS)

Napadlek, W.; Przetakiewicz, W.

2003-01-01

In the article were described investigations results of mechanical properties (hardness, R 0.2 , R m , A 5 , Z) and fatigue properties (rotary bending) of the 40H steel samples, being quenched and tempered, induction and laser hardened. In the laser hardened samples with weld penetration of top layer cracking process in fatigue strength is started mainly in weld penetration area as structural notch. (author)

The effects of ion irradiation on the micromechanical fracture strength and hardness of a self-passivating tungsten alloy

Energy Technology Data Exchange (ETDEWEB)

Lessmann, Moritz T., E-mail: mor.lessmann@gmail.com [School of Mechanical Aerospace and Civil Engineering, The University of Manchester, Manchester (United Kingdom); CCFE, Culham Science Centre, Abingdon (United Kingdom); Sudić, Ivan; Fazinić, Stjepko; Tadić, Tonči [Rudjer Bošković Institute, Bijenička cesta 54, 10000 Zagreb (Croatia); Calvo, Aida [Ceit-IK4 and Tecnun (University of Navarra), San Sebastian (Spain); Hardie, Christopher D.; Porton, Michael [CCFE, Culham Science Centre, Abingdon (United Kingdom); García-Rosales, Carmen [Ceit-IK4 and Tecnun (University of Navarra), San Sebastian (Spain); Mummery, Paul M. [School of Mechanical Aerospace and Civil Engineering, The University of Manchester, Manchester (United Kingdom)

2017-04-01

An ultra-fine grained self-passivating tungsten alloy (W88-Cr10-Ti2 in wt.%) has been implanted with iodine ions to average doses of 0.7 and 7 dpa, as well as with helium ions to an average concentration of 650 appm. Pile-up corrected Berkovich nanoindentation reveals significant irradiation hardening, with a maximum hardening of 1.9 GPa (17.5%) observed. The brittle fracture strength of the material in all implantation conditions was measured through un-notched cantilever bending at the microscopic scale. All cantilever beams failed catastrophically in an intergranular fashion. A statistically confirmed small decrease in strength is observed after low dose implantation (−6%), whilst the high dose implantation results in a significant increase in fracture strength (+9%), further increased by additional helium implantation (+16%). The use of iodine ions as the implantation ion type is justified through a comparison of the hardening behaviour of pure tungsten under tungsten and iodine implantation.

Corrosion and Fatigue Behavior of High-Strength Steel Treated with a Zn-Alloy Thermo-diffusion Coating

Science.gov (United States)

Mulligan, C. P.; Vigilante, G. N.; Cannon, J. J.

2017-11-01

High and low cycle fatigue tests were conducted on high-strength steel using four-point bending. The materials tested were ASTM A723 steel in the as-machined condition, grit-blasted condition, MIL-DTL-16232 heavy manganese phosphate-coated condition, and ASTM A1059 Zn-alloy thermo-diffusion coated (Zn-TDC). The ASTM A723 steel base material exhibits a yield strength of 1000 MPa. The effects of the surface treatments versus uncoated steel were examined. The fatigue life of the Zn-TDC specimens was generally reduced on as-coated specimens versus uncoated or phosphate-coated specimens. Several mechanisms are examined including the role of compressive residual stress relief with the Zn-TDC process as well as fatigue crack initiation from the hardened Zn-Fe alloy surface layer produced in the gas-metal reaction. Additionally, the effects of corrosion pitting on the fatigue life of coated specimens are explored as the Zn-TDC specimens exhibit significantly improved corrosion resistance over phosphate-coated and oiled specimens.

Formation of dislocations and hardening of LiF under high-dose irradiation with 5-21 MeV {sup 12}C ions

Energy Technology Data Exchange (ETDEWEB)

Zabels, R.; Manika, I.; Maniks, J.; Grants, R. [Institute of Solid State Physics, University of Latvia, Riga (Latvia); Schwartz, K. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Dauletbekova, A.; Baizhumanov, M. [L.N. Gumilyov Eurasian National University, Astana (Kazakhstan); Zdorovets, M. [Institute of Nuclear Physics, Almaty (Kazakhstan)

2017-05-15

The emergence of dislocations and hardening of LiF crystals irradiated to high doses with {sup 12}C ions have been investigated using chemical etching, AFM, nanoindentation, and thermal annealing. At fluences ensuring the overlapping of tracks (Φ ≥6 x 10{sup 11} ions/cm{sup 2}), the formation of dislocation-rich structure and ion-induced hardening is observed. High-fluence (10{sup 15} ions/cm{sup 2}) irradiation with {sup 12}C ions causes accumulation of extended defects and induces hardening comparable to that reached by heavy ions despite of large differences in ion mass, energy, energy loss, and track morphology. The depth profiles of hardness indicate on a notable contribution of elastic collision mechanism (nuclear loss) in the damage production and hardening. The effect manifests at the end part of the ion range and becomes significant at high fluences (≥10{sup 14} ions/cm{sup 2}). (orig.)

Development of high strength hot rolled low carbon copper-bearing steel containing nanometer sized carbides

Energy Technology Data Exchange (ETDEWEB)

Phaniraj, M.P. [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Shin, Young-Min [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Lee, Joonho [Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Goo, Nam Hoon [Sheet Product Design Group, Hyundai Steel Co., North Industrial Street 1400, 343-823, DangJin 343-823 (Korea, Republic of); Kim, Dong-Ik; Suh, Jin-Yoo; Jung, Woo-Sang [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Shim, Jae-Hyeok, E-mail: jhshim@kist.re.kr [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Choi, In-Suk, E-mail: insukchoi@kist.re.kr [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)

2015-05-01

A low carbon ferritic steel was alloyed with Ti, Mo and Cu with the intention of achieving greater increment in strength by multiple precipitate strengthening. The steel is hot rolled and subjected to interrupted cooling to enable precipitation of Ti–Mo carbides and copper. Thermodynamic calculations were carried out to determine equilibrium phase fractions at different temperatures. Microstructure characterization using transmission electron microscopy and composition analysis revealed that the steel contains ~5 nm size precipitates of (Ti,Mo)C. Precipitation kinetics calculations using MatCalc software showed that mainly body centered cubic copper precipitates of size < 5nm form under the cooling conditions in the present study. The steel has the high tensile strength of 853 MPa and good ductility. The yield strength increases by 420 MPa, which is more than that achieved in hot rolled low carbon ferritic steels with only copper precipitates or only carbide precipitates. The precipitation and strengthening contribution of copper and (Ti,Mo)C precipitates and their effect on the work hardening behavior is discussed.

Role of interfaces i nthe design of ultra-high strength, radiation damage tolerant nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Misra, Amit [Los Alamos National Laboratory; Wang, Yongqiang [Los Alamos National Laboratory; Nastasi, Michael A [Los Alamos National Laboratory; Baldwin, Jon K [Los Alamos National Laboratory; Wei, Qiangmin [Los Alamos National Laboratory; Li, Nan [Los Alamos National Laboratory; Mara, Nathan [Los Alamos National Laboratory; Zhang, Xinghang [Los Alamos National Laboratory; Fu, Engang [Los Alamos National Laboratory; Anderoglu, Osman [Los Alamos National Laboratory; Li, Hongqi [Los Alamos National Laboratory; Bhattacharyya, Dhriti [NON LANL

2010-12-09

The combination of high strength and high radiation damage tolerance in nanolaminate composites can be achieved when the individual layers in these composites are only a few nanometers thick and contain special interfaces that act both as obstacles to slip, as well as sinks for radiation-induced defects. The morphological and phase stabilities and strength and ductility of these nano-composites under ion irradiation are explored as a function of layer thickness, temperature and interface structure. Magnetron sputtered metallic multilayers such as Cu-Nb and V-Ag with a range of individual layer thickness from approximately 2 nm to 50 nm and the corresponding 1000 nm thick single layer films were implanted with helium ions at room temperature. Cross-sectional Transmission Electron Microscopy (TEM) was used to measure the distribution of helium bubbles and correlated with the helium concentration profile measured vis ion beam analysis techniques to obtain the helium concentration at which bubbles are detected in TEM. It was found that in multilayers the minimum helium concentration to form bubbles (approximately I nm in size) that are easily resolved in through-focus TEM imaging was several atomic %, orders of magnitude higher than that in single layer metal films. This observation is consistent with an increased solubility of helium at interfaces that is predicted by atomistic modeling of the atomic structures of fcc-bcc interfaces. At helium concentrations as high as 7 at.%, a uniform distribution of I nm diameter bubbles results in negligible irradiation hardening and loss of deformability in multi layers with layer thicknesses of a few nanometers. The control of atomic structures of interfaces to produce high helium solubility at interfaces is crucial in the design of nano-composite materials that are radiation damage tolerant. Reduced radiation damage also leads to a reduction in the irradiation hardening, particularly at layer thickness of approximately 5 run

Effect of solute elements on hardening of thermally-aged RPV model alloys

International Nuclear Information System (INIS)

Nomoto, A.; Nishida, K.; Dohi, K.; Soneda, N.; Liu, L.; Sekimura, N.; Li, Z.

2015-01-01

Embrittlement correlation methods for irradiated reactor pressure vessel (RPV) steels have been developed worldwide to predict the amount of embrittlement during plant operation. The effect of chemical composition on embrittlement is not fully understood, particularly the process of solute atom behavior during solute atom formation. In this series of slides we report the results of thermal ageing experiments of RPV model alloys in order to obtain information on the effect of chemical composition on the hardening process. We can draw the following conclusions. First, the addition of Ni or Si alone to Fe-Cu model alloys does not have clear effect but the addition of Mn to Fe-Cu-Ni alloy accelerates the cluster formation and hardening drastically, the effect of composition on the cluster strength is not clear. Secondly, the hardening process before the hardening peak has linear correlation with APT (Atom Probe Tomography) results and the RSS (Root-Sum-Square)sum model seems to explain the relationship between increase in hardness and APT data in a more consistent manner

Effect of strain rate and temperature on strain hardening behavior of a dissimilar joint between Ti–6Al–4V and Ti17 alloys

International Nuclear Information System (INIS)

Wang, S.Q.; Liu, J.H.; Chen, D.L.

2014-01-01

Highlights: • Only stage III hardening occurs after yielding in Ti–6Al–4V/Ti17 dissimilar joints. • Voce stress and strength of the joints increase with increasing strain rate. • With increasing strain rate, hardening capacity and strain hardening exponent decrease. • With increasing temperature, hardening capacity and strain hardening exponent increase. • Strain rate sensitivity of the joints decreases as the true strain increases. - Abstract: The aim of this study was to evaluate the influence of strain rate and temperature on the tensile properties, strain hardening behavior, strain rate sensitivity, and fracture characteristics of electron beam welded (EBWed) dissimilar joints between Ti–6Al–4V and Ti17 (Ti–5Al–4Mo–4Cr–2Sn–2Zr) titanium alloys. The welding led to significant microstructural changes across the joint, with hexagonal close-packed martensite (α′) and orthorhombic martensite (α″) in the fusion zone (FZ), α′ in the heat-affected zone (HAZ) on the Ti–6Al–4V side, and coarse β in the HAZ on the Ti17 side. A distinctive asymmetrical hardness profile across the dissimilar joint was observed with the highest hardness in the FZ and a lower hardness on the Ti–6Al–4V side than on the Ti17 side, where a soft zone was present. Despite a slight reduction in ductility, the yield strength (YS) and ultimate tensile strength (UTS) of the joints lay in-between the two base metals (BMs) of Ti–6Al–4V and Ti17, with the Ti17 alloy having a higher strength. While the YS, UTS, and Voce stress of the joints increased, both hardening capacity and strain hardening exponent decreased with increasing strain rate or decreasing temperature. Stage III hardening occurred in the joints after yielding. The hardening rate was strongly dependent on the strain rate and temperature. As the strain rate increased or temperature decreased, the strain hardening rate increased at a given true stress. The strain rate sensitivity evaluated via

Tensile properties and strain-hardening behavior of double-sided arc welded and friction stir welded AZ31B magnesium alloy

International Nuclear Information System (INIS)

Chowdhury, S.M.; Chen, D.L.; Bhole, S.D.; Cao, X.; Powidajko, E.; Weckman, D.C.; Zhou, Y.

2010-01-01

Microstructures, tensile properties and work hardening behavior of double-sided arc welded (DSAWed) and friction stir welded (FSWed) AZ31B-H24 magnesium alloy sheet were studied at different strain rates. While the yield strength was higher, both the ultimate tensile strength and ductility were lower in the FSWed samples than in the DSAWed samples due to welding defects present at the bottom surface in the FSWed samples. Strain-hardening exponents were evaluated using the Hollomon relationship, the Ludwik equation and a modified equation. After welding, the strain-hardening exponents were nearly twice that of the base metal. The DSAWed samples exhibited stronger strain-hardening capacity due to the larger grain size coupled with the divorced eutectic structure containing β-Mg 17 Al 12 particles in the fusion zone, compared to the FSWed samples and base metal. Kocks-Mecking type plots were used to show strain-hardening stages. Stage III hardening occurred after yielding in both the base metal and the welded samples. At lower strains a higher strain-hardening rate was observed in the base metal, but it decreased rapidly with increasing net flow stress. At higher strains the strain-hardening rate of the welded samples became higher, because the recrystallized grains in the FSWed and the larger re-solidified grains coupled with β particles in the DSAWed provided more space to accommodate dislocation multiplication during plastic deformation. The strain-rate sensitivity evaluated via Lindholm's approach was observed to be higher in the base metal than in the welded samples.

Structural heredity influence upon principles of strain wave hardening

Science.gov (United States)

Kiricheck, A. V.; Barinov, S. V.; Yashin, A. V.

2017-02-01

It was established experimentally that by penetration of a strain wave through material hardened not only the technological modes of processing, but also a technological heredity - the direction of the fibers of the original macrostructure have an influence upon the diagram of microhardness. By penetration of the strain wave along fibers, the degree of hardening the material is less, however, a product is hardened throughout its entire section mainly along fibers. In the direction of the strain waves across fibers of the original structure of material, the degree of material hardening is much higher, the depth of the hardened layer with the degree of hardening not less than 50% makes at least 3 mm. It was found that under certain conditions the strain wave can completely change the original structure of the material. Thus, a heterogeneously hardened structure characterized by the interchange of harder and more viscous areas is formed, which is beneficial for assurance of high operational properties of material.

Effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete

Science.gov (United States)

Memon, Fareed Ahmed; Nuruddin, Muhd Fadhil; Shafiq, Nasir

2013-02-01

The effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete (SCGC) was investigated in this paper. The work focused on the concrete mixes with a fixed water-to-geopolymer solid (W/Gs) ratio of 0.33 by mass and a constant total binder content of 400 kg/m3. The mass fractions of silica fume that replaced fly ash in this research were 0wt%, 5wt%, 10wt%, and 15wt%. The workability-related fresh properties of SCGC were assessed through slump flow, V-funnel, and L-box test methods. Hardened concrete tests were limited to compressive, splitting tensile and flexural strengths, all of which were measured at the age of 1, 7, and 28 d after 48-h oven curing. The results indicate that the addition of silica fume as a partial replacement of fly ash results in the loss of workability; nevertheless, the mechanical properties of hardened SCGC are significantly improved by incorporating silica fume, especially up to 10wt%. Applying this percentage of silica fume results in 4.3% reduction in the slump flow; however, it increases the compressive strength by 6.9%, tensile strength by 12.8% and flexural strength by 11.5%.

Numerical simulation of the roll levelling of third generation fortiform 1050 steel using a nonlinear combined hardening material model

Science.gov (United States)

Galdos, L.; Saenz de Argandoña, E.; Mendiguren, J.; Silvestre, E.

2017-09-01

The roll levelling is a flattening process used to remove the residual stresses and imperfections of metal strips by means of plastic deformations. During the process, the metal sheet is subjected to cyclic tension-compression deformations leading to a flat product. The process is especially important to avoid final geometrical errors when coils are cold formed or when thick plates are cut by laser. In the last years, and due to the appearance of high strength materials such as Ultra High Strength Steels, machine design engineers are demanding reliable tools for the dimensioning of the levelling facilities. Like in other metal forming fields, finite element analysis seems to be the most widely used solution to understand the occurring phenomena and to calculate the processing loads. In this paper, the roll levelling process of the third generation Fortiform 1050 steel is numerically analysed. The process has been studied using the MSC MARC software and two different material laws. A pure isotropic hardening law has been used and set as the baseline study. In the second part, tension-compression tests have been carried out to analyse the cyclic behaviour of the steel. With the obtained data, a new material model using a combined isotropic-kinematic hardening formulation has been fitted. Finally, the influence of the material model in the numerical results has been analysed by comparing a pure isotropic model and the later combined mixed hardening model.

Mechanical Properties and Durability of Ultra High Strength Concrete Incorporating Multi-Walled Carbon Nanotubes.

Science.gov (United States)

Lu, Liulei; Ouyang, Dong; Xu, Weiting

2016-05-27

In this work, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and durability of ultra high strength concrete (UHSC) is reported. First, the MWCNTs were dispersed by a nano sand-mill in the presence of a surfactant in water. The UHSC specimens were prepared with various amounts of MWCNTs, ranging from 0% to 0.15% by weight of cement (bwoc). Results indicated that use of an optimal percentage of MWCNTs (0.05% bwoc) caused a 4.63% increase in compressive strength and a 24.0% decrease in chloride diffusion coefficient of UHSC at 28 days curing. Moreover, the addition of MWCNTs also improved the flexural strength and deformation ability. Furthermore, a field-emission scanning electron microscopy (FE-SEM) was used to observe the dispersion of MWCNTs in the cement matrix and morphology of the hardened cement paste containing MWCNTs. FE-SEM observation revealed that MWCNTs were well dispersed in the matrix and no agglomerate was found and the reinforcing effect of MWCNTs on UHSC was thought to be pulling out and microcrack bridging of MWCNTs, which transferred the load in tension.

Nano-twin mediated plasticity in carbon-containing FeNiCoCrMn high entropy alloys

Energy Technology Data Exchange (ETDEWEB)

Wu, Z. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996 (United States); Parish, C.M. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Bei, H., E-mail: beih@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2015-10-25

Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. The effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. The materials can be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (∼70% at 77 K and ∼40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys. - Highlights: • Interstitial atom C was successfully added into FeNiCoCrMn high entropy alloys. • The strain hardening rate and strength are enhanced in the C-containing alloy. • The increased strain-hardening and strength are caused by the nano-twinning.

In-situ neutron diffraction study on work-hardening behavior in a ferrite-martensite dual phase steel

OpenAIRE

Morooka, Satoshi; Sato, Naoko; Ojima, Mayumi; Harjo, Stefanus; Adachi, Yoshitaka; Tomota, Yo; Umezawa, Osamu

2011-01-01

Strength and work-hardening in steels have been discussed from the viewpoint of heterogeneous deformation. In-situ neutron diffraction techniques made clear that the misfit strains between grains accompanied with the grain-scaled internal stress (intergranular stress). In the dual phase steel, the intergranular stress was superposed on phase stress. Both long-range internal stress and short-range one like forest dislocation hardening may cause the resistance for dislocation motion in the steels.

Hardening by annealing and softening by deformation in nanostructured metals

DEFF Research Database (Denmark)

Huang, X.; Hansen, N.; Tsuji, N.

2006-01-01

We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation-dislocation and ......We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation....... As a consequence, the strength decreases and the ductility increases. These observations suggest that for materials such as the nanostructured aluminum studied here, deformation should be used as an optimizing procedure instead of annealing....

The influence of calcium nitrate on setting and hardening rate of Portland cement concrete at different temperatures

Science.gov (United States)

Kičaitė, A.; Pundienė, I.; Skripkiūnas, G.

2017-10-01

Calcium nitrate in mortars and concrete is used as a multifunctional additive: as set accelerator, plasticizer, long term strength enhancer and as antifreeze admixture. Used binding material and the amount of calcium nitrate, affect the characteristics of the concrete mixture and strength of hardened concrete. The setting time of the initial and the final binding at different temperatures of hardening (+ 20 °C and + 5 °C) of the pastes made of different cements (Portland cement CEM I 42.5 R and Portland limestone cement CEM II/A-LL 42.5 R) and various amounts of calcium nitrate from 1 % until 3 % were investigated. The effect of calcium nitrate on technological characteristics of concrete mixture (the consistency of the mixture, the density, and the amount of air in the mixture), on early concrete strength after 2 and 7 days, as well as on standard concrete strength after 28 days at different temperatures (at + 20 °C and + 5 °C) were analysed.

Spall Strength Measurements in Transparent Epoxy Polymers

Science.gov (United States)

Pepper, Jonathan; Rahmat, Meysam; Petel, Oren

2017-06-01

Polymer nanocomposites are seeing more frequent use in transparent armour applications. The role of the microstructure on the performance of these materials under dynamic tensile loading conditions is of particular interest. In the present study, a series of plate impact experiments was conducted in order to evaluate the dynamic response of an epoxy (EPON 828) cured with two differed hardeners. The purpose was to compare the role of these hardeners on the dynamic performance of the resulting transparent epoxy. The material response was resolved with a multi-channel photonic Doppler velocimeter. This system was used to determine the shock Hugoniot and dynamic tensile (spall) strength of the materials. The experimental results are presented in reference to spall theory and are evaluated against results predicted by an analytical model of the impacts. While varying the hardener did not change the shock Hugoniot of the epoxy, it did have an effect on the measured spall strengths.

Radiation-hardened bulk CMOS technology

International Nuclear Information System (INIS)

Dawes, W.R. Jr.; Habing, D.H.

1979-01-01

The evolutionary development of a radiation-hardened bulk CMOS technology is reviewed. The metal gate hardened CMOS status is summarized, including both radiation and reliability data. The development of a radiation-hardened bulk silicon gate process which was successfully implemented to a commercial microprocessor family and applied to a new, radiation-hardened, LSI standard cell family is also discussed. The cell family is reviewed and preliminary characterization data is presented. Finally, a brief comparison of the various radiation-hardened technologies with regard to performance, reliability, and availability is made

Surface finishing and levelling of thermomechanically hardened rolled steel

International Nuclear Information System (INIS)

Grosval'd, V.G.; Bashchenko, A.P.; Grishkov, A.I.; Gutnik, M.V.; Kanevskij, B.L.; Nikozov, A.I.; Sedov, N.D.; Prosin, K.A.; Safonov, L.I.

1975-01-01

The finishing of high-strength merchant shapes from alloy steel was tried out under industrial conditions with the equipment of metallurgical plants. After thermomechanical hardening in the production line of the rolling mill, 30KhGSN2A and 40Kh1NVA steel rounds 32 and 31 mm in diameter were straightened on a two-roller straightening machine designed by the All-Union Scientific Research Institute for Metallurgical Machinery (VNII Metmash). This made possible subsequent turning and grinding of the rods. The conditions of straightening, turning and grinding have been worked so as to obtain thermomechanically strengthened and ground rolled products approximating the gauged and ground metal in shape geometry and surface finish. It is shown that the labour-consuming operation of turning can be eliminated by reducing the machining pass of the rolled product, and this lowers the labour required for the finishing operations by 75%. After grinding with 40- and 25-grain abrasive wheels, high strength rolled shapes were obtained with a diameter of 30-0.20 mm and a surface finish of class 6-5 satisfying the technical specifications. (author)

The influence of using accelerator addition on High strength self-compacting concrete (HSSCC) in case of enhancement early compressive strength and filling ability parameters

Science.gov (United States)

Wibowo; Fadillah, Y.

2018-03-01

Efficiency in a construction works is a very important thing. Concrete with ease of workmanship and rapid achievement of service strength will to determine the level of efficiency. In this research, we studied the optimization of accelerator usage in achieving performance on compressive strength of concrete in function of time. The addition of variation of 0.3% - 2.3% to the weight of cement gives a positive impact of the rapid achievement of hardened concrete, however the speed of increasing of concrete strength achievement in term of time influence present increasing value of filling ability parameter of self-compacting concrete. The right composition of accelerator aligned with range of the values standard of filling ability parameters of HSSCC will be an advantage guidance for producers in the ready-mix concrete industry.

High strength cast aluminum alloy development

Science.gov (United States)

Druschitz, Edward A.

The goal of this research was to understand how chemistry and processing affect the resulting microstructure and mechanical properties of high strength cast aluminum alloys. Two alloy systems were investigated including the Al-Cu-Ag and the Al-Zn-Mg-Cu systems. Processing variables included solidification under pressure (SUP) and heat treatment. This research determined the range in properties that can be achieved in BAC 100(TM) (Al-Cu micro-alloyed with Ag, Mn, Zr, and V) and generated sufficient property data for design purposes. Tensile, stress corrosion cracking, and fatigue testing were performed. CuAl2 and Al-Cu-Fe-Mn intermetallics were identified as the ductility limiting flaws. A solution treatment of 75 hours or longer was needed to dissolve most of the intermetallic CuAl 2. The Al-Cu-Fe-Mn intermetallic was unaffected by heat treatment. These results indicate that faster cooling rates, a reduction in copper concentration and a reduction in iron concentration might increase the ductility of the alloy by decreasing the size and amount of the intermetallics that form during solidification. Six experimental Al-Zn-Mg-Cu series alloys were produced. Zinc concentrations of 8 and 12wt% and Zn/Mg ratios of 1.5 to 5.5 were tested. Copper was held constant at 0.9%. Heat treating of the alloys was optimized for maximum hardness. Al-Zn-Mg-Cu samples were solution treated at 441°C (826°F) for 4 hours before ramping to 460°C (860°F) for 75 hours and then aged at 120°C (248°F) for 75 hours. X-ray diffraction showed that the age hardening precipitates in most of these alloys was the T phase (Mg32Zn 31.9Al17.1). Tensile testing of the alloys showed that the best mechanical properties were obtained in the lowest alloy condition. Chilled Al-8.2Zn-1.4Mg-0.9Cu solidified under pressure resulted in an alloy with a yield strength of 468MPa (68ksi), tensile strength of 525MPa (76ksi) and an elongation of 9%.

Online frequency adjustment for energy optimisation of induction hardening processes; Energetische Optimierung von Induktionshaertungsprozessen durch Online-Frequenzanpassung

Energy Technology Data Exchange (ETDEWEB)

Ulferts, Alexander; Andrae, Frank [HWG Inductoheat GmbH, Reichenbach (Germany)

2011-06-15

It is frequently necessary to harden multiple points on a component. The hardness specification may, in many cases, be variable, and the boundary conditions often diverse. The relevant sectors of the component are in many cases more deeply hardened, to enhance strength and vibration-fatigue properties, with simultaneous retention of ductile properties in the core, in order to reduce the danger of fracture of the heat-treated component in service. In other cases, the hardening process is intended more to provide protection against elevated surface loadings and against abrasive erosion of material. Both of these applications are illustrated on the basis of a component in the context of this article, and the requirements made on the inductive hardening process discussed. The authors consciously raise the question of the limits of technical feasibility. (orig.)

Hardening mechanisms of spray formed Al-Zn-Mg-Cu alloys with scandium and other elemental additions

International Nuclear Information System (INIS)

Sharma, M.M.; Amateau, M.F.; Eden, T.J.

2006-01-01

The hardening mechanisms in spray formed Al-Zn-Mg-Cu alloys with additions of chromium, zinc and scandium were studied. The microstructure of the spray formed alloys was analyzed by transmission electron microscopy. A range of tensile strengths were achieved, and varied based on elemental additions, and second phase particle strengthening. To explain the significantly higher strength in one alloy with scandium, theoretical results due to the yield stress of Al-Zn-Mg-Cu alloys as a function of volume fraction and precipitate particle size, were compared to experimental data. Both the possibilities of coherency and order strengthening are examined. The significant additional hardening achieved in the alloy with scandium is attributed to small ordered particles of Al 3 Sc, which precipitated during aging

Hardening device, by inserts, of electronic component against radiation

International Nuclear Information System (INIS)

Val, C.

1987-01-01

The hardening device includes at least two materials, one with high atomic number with respect to the other. One of these materials is set as inserts in a layer of the other material. The hardening device is then made by stacking of such layers, the insert density varying from one layer to the other, making thus vary the atomic number resulting from the hardening device along its thickness, following a predefined law [fr

Influence of the Hardener on the Emission of Harmful Substances from Moulding Sands with Furan Resin in the Pyrolysis Process

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Holtzer M.

2016-03-01

Full Text Available The furan resin offers advantages such as high intensity, low viscosity, good humidity resistance and is suitable for cast different casting alloys: steel, cast iron and non-ferrous metal casting. For hardening furan resins are used different hardeners (acid catalysts. The acid catalysts have significant effects on the properties of the cured binder (e,g. binding strength and thermal stability [1 - 3]. Investigations of the gases emission in the test foundry plant were performed according to the original method developed in the Faculty of Foundry Engineering, AGH UST. The analysis is carried out by the gas chromatography method with the application of the flame-ionising detector (FID (TRACE GC Ultra THERMO SCIENTIFIC.

Influence of Carbide Modifications on the Mechanical Properties of Ultra-High-Strength Stainless Steels

Science.gov (United States)

Seo, Joo-Young; Park, Soo-Keun; Kwon, Hoon; Cho, Ki-Sub

2017-10-01

The mechanical properties of ultra-high-strength secondary hardened stainless steels with varying Co, V, and C contents have been studied. A reduced-Co alloy based on the chemical composition of Ferrium S53 was made by increasing the V and C content. This changed the M2C-strengthened microstructure to a MC plus M2C-strengthened microstructure, and no deteriorative effects were observed for peak-aged and over-aged samples despite the large reduction in Co content from 14 to 7 wt pct. The mechanical properties according to alloying modification were associated with carbide precipitation kinetics, which was clearly outlined by combining analytical tools including small-angle neutron scattering (SANS) as well as an analytical TEM with computational simulation.

Effect of explosion hardening on the properties of the near-surface layer of glow-discharged nitrided 33H3MF steel

International Nuclear Information System (INIS)

Rudnicki, J.; Fleszar, A.; Wierzchon, T.; Maranda, A.; Nowaczewski, J.

1999-01-01

The study was concerned with the effect of explosion hardening of 33H3MF steel, realized by the impact of the detonation products of a metallic plate driven by the detonation of an explosive plastic material, upon the microhardness and thickness of the nitrided layers forming during the glow discharge assisted nitridation process. Nitrided layers containing a compound zone, diffusion layers and layers with braunite content were formed on explosion-hardened steel surfaces. The corrosion resistance of the nitrided layers thus obtained was compared with that of the layers formed on non-hardened surfaces and on non-hardened and nitrided surfaces. The layers examined have a higher corrosion resistance than the starting material, but lower than the nitrided layers formed without the explosive load. The impact strength of the steel samples was examined before and after the explosion hardening and also after glow discharge assisted nitriding. It has been found that the explosion hardening followed by nitriding increases the impact strength, which is an advantageous effect. This also gives evidence that the changes in the hardness and structure of the samples examined, which are only observed in the layers whose thickness falls between 0.1 and 1.5 mm do not affect the notch present on the sample surface and thus have no influence upon the character of the sample fracture. (author)

Unusual hardening behaviour in heavily cryo-rolled Cu-Al-Zn alloys during annealing treatment

Energy Technology Data Exchange (ETDEWEB)

Gong, Y.L. [Faculty of Science, Kunming University of Science and Technology, Kunming 650500 (China); Ren, S.Y. [Ningbo Powerway Alloy Material Co., Ltd, Ningbo 315135 (China); Zeng, S.D. [Yunnan Institute of Measuring and Testing Technology, Kunming 650228 (China); Zhu, X.K., E-mail: xk_zhu@hotmail.com [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650500 (China)

2016-04-06

Three nanostructured Cu-Al-Zn alloys were produced via rolling at the liquid nitrogen temperature. The deformed Cu alloys were then annealed at 150–300 °C for 1 h. The two alloys with high solute content and thus with low stacking fault energy exhibit unusual annealing hardening, namely, an increase in hardness and strength and a decrease in tensile elongation after annealing at 150 and 200 °C. From X-ray diffraction (XRD) analysis and microstructural observations by transmission electron microscopy (TEM), it is found that microstrain and dislocation density decrease after annealing at 200 °C because of the recovery of dislocations and the lattice parameter decreases due to solute segregation. Meanwhile, the twin density of the two Cu alloys increases and grain size remains basically unchanged. It is shown that the formation of annealing twins and stacking faults and the segregation of solute atoms may be the main causes of unusual annealing hardening.

Nanotechnological applied tasks of the increase in the efficiency of the hardening processes of cement concrete

Directory of Open Access Journals (Sweden)

Chernishov Evgeny Mihalovich

2017-02-01

Full Text Available The scientific basis of the solution to the applied tasks of concrete technology through the use of «nano» tools, which provide the organization of the heterogeneous process of cement hydration and hardening, has been characterized. It is shown that the introduction of nanoadditives enables the direct regulation of the processes of structure formation in cement systems at the nanolevel. The effectiveness of the use of «nano» tools has been proposed to evaluate by means of complex criteria characterizing quantitatively the change in the activation energy, the rate of the process and time of its completion τ, the size and power consumption of the technology E while ensuring quality levels specified by R. According to the criteria, the monitoring of the results of the research has been made. Moreover, the most effective nanomodifying admixtures of two types have been identified. Type I is a compound nanoadditive based on nanoparticles SiO2 in combination with a superplasticizer, which mechanism of action is associated and also characterized by the increase in specific strength per unit measure the degree of cement hydration by 1.25–1.35 times. Engineering problems have been formulated. Moreover, the solutions are indicated for increasing the energy efficiency of the factory production of reinforced concrete products and structures. These solutions predetermine the reduction in the value of the maximum temperature for the curing of concrete, the reduction of the duration of the achievement of the required degree of cement hydration while concrete hardens, the reduction of time of cement concrete hardening to reach the regulated values of its strength, the increase in concrete strength per unit of cement consumption per m3 and energy efficiency of concrete hardening process in the preparation of reinforced concrete products. with the catalytic role in the processes of phase formation of nanoparticles of hydrated compounds. Type II is a

Deflection hardening behaviour of short fibre reinforced fly ash based geopolymer composites

International Nuclear Information System (INIS)

Shaikh, F.U.A.

2013-01-01

Highlights: • Deflection hardening behaviour is achieved in the DFRGC similar to that observed in DFRCC. • The first crack load or in other word the limit of proportionality (LOP) of DFRGC is similar to that of DFRCC. • The DFRGC also exhibited higher deflection at peak load than DFRCC. • The toughness at peak load of DFRGC is also high than that of DFRCC. • The ductility of DFRGC is also higher than that of DFRCC. - Abstract: This paper reports the newly developed ductile fibre reinforced geopolymer composite (DFRGC) exhibiting deflection hardening and multiple cracking behaviour. The binder of the above composite is different from that used in conventional cement based system. The class F fly ash is used instead of Portland cement in DFRGC and is activated by alkaline liquids (sodium hydroxide and sodium silicate). In this study, two types of fibres namely steel (ST) and polyvinyl alcohol (PVA) fibres are used in mono as well as in ST–PVA hybrid form, with a total volume fraction of 2%. The deflection hardening behaviour of newly developed DFRGC is also compared with that of conventional ductile fibre reinforced cementitious composites (DFRCC). The effects of two different sizes of sand (1.18 mm, and 0.6 mm) and sand/binder ratios of 0.5 and 0.75 on the deflection hardening and multiple cracking behaviour of both DFRGC and DFRCC are also evaluated. Results revel that the deflection hardening and multiple cracking behaviour is achieved in geopolymer based DFRGC similar to that of cement based system. For a given sand size and sand content, comparable deflection hardening behaviour, ultimate flexural strength and the deflection at peak load are observed in both cement and geopolymer based composites irrespective of fibre types and combination. The deflection hardening behaviour of DFRGC is also confirmed by the calculated toughness index values of I 20 > 20. The scanning electron microscope (SEM) study shows no degradation of PVA and steel fibres in the

Characterization of Tool Wear in High-Speed Milling of Hardened Powder Metallurgical Steels

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Fritz Klocke

2011-01-01

Full Text Available In this experimental study, the cutting performance of ball-end mills in high-speed dry-hard milling of powder metallurgical steels was investigated. The cutting performance of the milling tools was mainly evaluated in terms of cutting length, tool wear, and cutting forces. Two different types of hardened steels were machined, the cold working steel HS 4-2-4 PM (K490 Microclean/66 HRC and the high speed steel HS 6-5-3 PM (S790 Microclean/64 HRC. The milling tests were performed at effective cutting speeds of 225, 300, and 400 m/min with a four fluted solid carbide ball-end mill (0 = 6, TiAlN coating. It was observed that by means of analytically optimised chipping parameters and increased cutting speed, the tool life can be drastically enhanced. Further, in machining the harder material HS 4-2-4 PM, the tool life is up to three times in regard to the less harder material HS 6-5-3 PM. Thus, it can be assumed that not only the hardness of the material to be machined plays a vital role for the high-speed dry-hard cutting performance, but also the microstructure and thermal characteristics of the investigated powder metallurgical steels in their hardened state.

Configurable Radiation Hardened High Speed Isolated Interface ASIC, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — NVE Corporation will design and build an innovative, low cost, flexible, configurable, radiation hardened, galvanically isolated, interface ASIC chip set that will...

Radiation-hardened control system

International Nuclear Information System (INIS)

Vandermolen, R.I.; Smith, S.F.; Emery, M.S.

1993-01-01

A radiation-hardened bit-slice control system with associated input/output circuits was developed to prove that programmable circuits could be constructed to successfully implement intelligent functions in a highly radioactive environment. The goal for this effort was to design and test a programmable control system that could withstand a minimum total dose of 10 7 rads (gamma). The Radiation Hardened Control System (RHCS) was tested in operation at a dose rate that ranged up to 135 krad/h, with an average total dose of 10.75 Mrads. Further testing beyond the required 10 7 rads was also conducted. RHCS performed properly through the target dose of 10 7 rads, and sporadic intermittent failures in some programmable logic devices were noted after ∼ 13 Mrads

A non-linear kinematic hardening function

International Nuclear Information System (INIS)

Ottosen, N.S.

1977-05-01

Based on the classical theory of plasticity, and accepting the von Mises criterion as the initial yield criterion, a non-linear kinematic hardening function applicable both to Melan-Prager's and to Ziegler's hardening rule is proposed. This non-linear hardening function is determined by means of the uniaxial stress-strain curve, and any such curve is applicable. The proposed hardening function considers the problem of general reversed loading, and a smooth change in the behaviour from one plastic state to another nearlying plastic state is obtained. A review of both the kinematic hardening theory and the corresponding non-linear hardening assumptions is given, and it is shown that material behaviour is identical whether Melan-Prager's or Ziegler's hardening rule is applied, provided that the von Mises yield criterion is adopted. (author)

Laser transformation hardening effect on hardening zone features and surface hardness of tool steel AISI D2

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D. Lesyk

2017-06-01

Full Text Available The relationship of technological input regimes of the laser transformation hardening on change the hardening depth, hardening width, and hardening angle, as well as surface hardness of the tool steel AISI D2 using multifactor experiment with elements of the analysis of variance and regression equations was determined. The laser transformation hardening process implemented by controlling the heating temperature using Nd:YAG fiber laser with scanner, pyrometer and proportional-integral-differential controller. The linear and quadratic regression models are developed, as well as response surface to determine the effect of the heating temperature and feed rate of the treated surface on the energy density of the laser beam, hardening depths, hardening width, hardening angle, and surface hardness are designed. The main effect on the energy density of the laser beam has a velocity laser treatment, on the other hand, the main effect on the geometrical parameters of the laser hardened zone and surface hardness has temperature heating are shown. The optimum magnitudes of the heating temperature (1270 °C and feed rate of the treated surface (90 mm/min for laser transformation hardening of the tool steel AISI D2 using fiber laser with scanner were defined.

Precipitation Effect on Mechanical Properties and Phase Stability of High Manganese Steel

Science.gov (United States)

Bae, Cheoljun; Kim, Rosa; Lee, Un-Hae; Kim, Jongryoul

2017-09-01

High manganese (Mn) steels are attractive for automotive applications due to their excellent tensile strength and superior elongation. However, the relatively low yield strength of Mn steels compared to other advanced high-strength steels is a critical problem limiting their use in structural parts. In order to increase the yield strength, the precipitation hardening effect of Mn steels was investigated by the addition of carbide-forming elements. Changes in the austenite phase stability were also evaluated in terms of stacking fault energy (SFE). As a result, fine V(C,N) precipitates were found to increase the yield strength effectively but to lower the SFE by the consumption of matrix carbons. For achieving precipitation hardening without sacrificing austenite stability, the soluble carbon content was discussed.

Precipitation Strengthening by Induction Treatment in High Strength Low Carbon Microalloyed Hot-Rolled Plates

Science.gov (United States)

Larzabal, G.; Isasti, N.; Rodriguez-Ibabe, J. M.; Uranga, P.

2018-03-01

The use of microalloyed steels in the production of thick plates is expanding due to the possibility of achieving attractive combinations of strength and toughness. As market requirements for high strength plates are increasing and new applications require reduced weight and innovative designs, novel approaches to attaining cost-effective grades are being developed. The mechanism of precipitation strengthening has been widely used in thin strip products, since the optimization of the coiling strategy offers interesting combinations in terms of final properties and microalloying additions. Precipitation strengthening in thick plates, however, is less widespread due to the limitation of interphase precipitation during continuous cooling after hot rolling. With the main objective of exploring the limits of this strengthening mechanism, laboratory thermomechanical simulations that reproduced plate hot rolling mill conditions were performed using low carbon steels microalloyed with Nb, NbMo, and TiMo additions. After continuous cooling to room temperature, a set of heat treatments using fast heating rates were applied simulating the conditions of induction heat treatments. An important increase of both yield and tensile strengths was measured after induction treatment without any important impairment in toughness properties. A significant precipitation hardening is observed in Mo-containing grades under specific heat treatment parameters.

Microhardness technique for determination of radiation hardening in austenitic stainless steel using

International Nuclear Information System (INIS)

Hofman, A.

1995-01-01

The use of microhardness technique to determine the radiation hardening has been studied. Microhardness measurements have been conducted on austenitic stainless steel 0H18N10T irradiated up to 2·10 23 nm -2 . It was determined that the increase in microhardness varies directly with the measured increase in the 0,2% offret yield strength and has been found that microhardness technique may be an effective tool to measurements of radiation induced hardening. Based on the results and Cahoon's relation that σ 0,2 (MPa)=3,27HV(0,1) n method for evaluating the yield stress σ 0,2 by microhardness technique is analyzed. 14 refs., 3 figs., 3 tabs

Concurrent strengthening of ultrafine-grained age-hardenable Al-Mg alloy by means of high-pressure torsion and spinodal decomposition

International Nuclear Information System (INIS)

Tang, Yongpeng; Goto, Wataru; Hirosawa, Shoichi; Horita, Zenji; Lee, Seungwon; Matsuda, Kenji; Terada, Daisuke

2017-01-01

In this study, the age-hardening behavior and precipitate microstructures of severely-deformed and then artificially-aged Al-13.4 wt%Mg alloy has been investigated by Vickers hardness test, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and atom probe tomography (APT). The combined processing of high-pressure torsion (HPT) and aging treatment at a temperature below spinodal lines results in a higher attained hardness of ∼HV296 with an age-hardenability (i.e ΔHV31 ± 2) comparable to that of the undeformed specimen without HPT (i.e. ΔHV33 ± 2). The corresponding TEM microstructures consist of modulated structures associated with spinodal decomposition, and quantitative estimation of the amplitude, as well as the wavelength, of Mg fluctuations was successfully conducted by APT for the first time for this alloy system. The linear relationship between the increment of Vickers hardness and the estimated amplitude of the undeformed specimen supposed that Kato's spinodal-hardening mechanism works even in the HPTed specimen with a high number density of grain boundaries. Therefore, our proposed strategy; i.e. taking advantage of spinodal decomposition, is regarded as a convincing approach to achieving concurrent strengthening by ultrafine-grained and precipitation hardenings for the alloys that decompose via spinodal decomposition.

Changes in Structural Characteristics of Hypoeutectic Al-Si Cast Alloy after Age Hardening

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Lenka HURTALOVÁ

2012-09-01

Full Text Available The contribution describes influence of the age-hardening consist of solution treatment at 515 °C with holding time 4 hours, water quenching at 40 °C and artificial aging at different temperature 150 °C, 170 °C and 190 °C with different holding time 2, 4, 8, 16 and 32 hours on mechanical properties (tensile strength and Brinell hardness and changes in morphology of eutectic Si, Fe-rich and Cu-rich intermetallic phases in secondary (recycled AlSi9Cu3 cast alloy. A combination of different analytical techniques (light microscopy upon black-white and colour etching, scanning electron microscopy (SEM upon deep etching and energy dispersive X-ray analysis (EDX were therefore been used for the identification of the various phases. Quantitative study of changes in morphology of eutectic Si, Cu-rich and Fe-rich phases was carried out using Image Analyzer software NIS-Elements. Mechanical properties were measured in line with EN ISO. Age-hardening led to changes in microstructure include the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe- rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al2Cu further increase in the hardness and tensile strength in the alloy.DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2430

IMPROVEMENT OF EQUIPMENT FOR EFFECTIVE HARDENING SAND MIXTURE BY VACUUM MOLDING

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V. S. Doroshenko

2016-01-01

Full Text Available The review deals with the design flask tooling and patterns for effective hardening sand mixture in the vacuum molding (V-Process, and molding on a one-off patterns (Lost Foam Casting. Sealing and evacuating sand mixture – two major factors influence the strength of the casting mold and casting quality, management practices which will enable to improve the casting process.

Superheat effect on bainite steel hardenability

International Nuclear Information System (INIS)

Kubachek, V.V.; Sklyuev, P.V.

1978-01-01

The bainite hardenability of 34KhN1M and 35 KhN1M2Ph steels has been investigated by the end-face hardening technique. It is established that, as the temperature of austenitization rises from 900 to 1280 deg C, the temperature of bainite transformation increases and bainite hardenability of the steels falls off. A repeated slow heating to 900 deg C of previously overheated 34KhN1M steel breaks up grain, lowers the temperature of the bainite transformation and raises the hardenability to values obtained with ordinary hardening from 900 deg C. A similar heating of previously overheated 35KhN1M2Ph steel is accompanied by restoration of initial coarse grains and maintenance of both the elevated bainite transformation temperature and to lower hardenability corresponding to hardening from the temperature of previous overheating

HARDENING OF CRANE RAILS BY PLASMA DISCRETE-TIME SURFACE TREATMENT

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S. S. Samotugin

2017-01-01

Full Text Available Crane wheels and rails are subjected to intensive wear in the process of operation. Therefore, improvement of these components’ performance can be considered a task of high importance. A promising direction in this regard is surface treatment by highly concentrated energy flows such as laser beams or plasma jets. This thesis suggests that the use of gradient plasma surface treatment can improve the performance of crane rails. A research was conducted, according to which hardened zones were deposited on crane rails under different treatment modes. Microhardness was measured both at the surface and in depth using custom-made microsections. The article includes the results of study of plasma surface hardening effects on wear resistance of crane rails. Change of plasma surface treatment parameters (current, plasma torch movement speed, argon gas flow rate allows for desired steel hardness and structure, while the choice of optimal location for hardened zones makes it possible to significantly improve wear resistance and crack resistance. As a result of plasma surface hardening, the fine-grained martensite structure is obtained with mainly lamellar morphology and higher hardness rate compared toinduction hardening or overlaying. Wear test of carbon steels revealed that plasma surfacing reduces abrasive wear rate compared to the irinitial state by 2 to 3 times. Enough sharp boundary between hardened and non-hardened portions has a positive effect on the performance of parts under dynamic loads, contributing to the inhibition of cracks during the transition from solid to a soft metal. For carbon and low alloy rail steels, the properties achieved by plasma surface hardening can effectively replace induction hardening or overlaying.The mode range for plasma surface treatment that allow sobtaining a surface layer with certain operating properties has been determined.

The formation of structures and properties of carburized elements and hardened in different quenching medium

International Nuclear Information System (INIS)

Przylecka, M.; Gestwa, W.

2003-01-01

In work structure and selected properties of hardened carburized layers were introduced produced on chromium-manganese steel (16HG - 16CrMn5), after processes of gas carburizing (850 o C/1-10 h) and vacuum carburizing (950 o C/2 h) as well as direct hardening (center cooling: distillated water, Water polymer solution - polyglycol oxyalkylen, oil and gas-nitrogen) and tempering. Results of investigations permitted to affirm, that layer with structure martensite - retained austenite, as carbides - martensite - retained austenite produced in process of hardening applying cooling centre water polymer solution, the impact strength of element (at define thickness of carburized layer) give profitable, suitable hardness and microhardness as well as changes of microhardness on section in comparison to produced layers during cooling in water or oil and gas. (author)

Evaluation of hardening by ion irradiation in molybdenum using nanoindentation techniques

International Nuclear Information System (INIS)

Iwakiri, Hirotomi; Watanabe, Hideo; Yoshida, Naoaki

1997-01-01

As a part of fundamental research on interaction of plasma and wall, some model experiments on loading of particles such as He, H and so forth suffered by plasma facing material were conducted for Mo in high Z material. As an evaluation method for it, nanoindentation technique was proposed. By this method, the hardness evaluation in surface neighboring damage range was conducted. As a result, in the helium irradiated materials, sufficient hardening was observed even at low dpa range impossible to recognize hardening on heavy ion and deuterium irradiated materials, and extreme hardening was established by formation of helium bubble at high dpa region. Furthermore, in the helium irradiated materials, recovery of hardening could not be observed even for annealed materials at 1173 K for 1 hr after irradiation. From such results, hardening promotion work due to helium and extreme thermal stability of the formed defects were elucidated. (B.K.)

Account of low temperature hardening in calculation of permissible stresses

International Nuclear Information System (INIS)

Novikov, N.V.; Ul'yanenko, A.P.; Gorodyskij, N.I.

1980-01-01

Suggested is a calculation scheme of permissible stresses with the account of temperature hardening for steels and alloys, the dependences of strength, plasticity and rupture work of which on cooling temperature do not have threshold changes in a wide range of low temperatures (from 300 to 4.2 K). Application of the suggested scheme is considered on the example of 12Kh18N10T austenitic chromium-nickel steel

IMPACT OF FORMULA-TECHNOLOGICAL FACTORS ON CONCRETE STRENGTH INDICATORS FOR INJECTING WITH TWO-STAGE EXPANSION

Directory of Open Access Journals (Sweden)

Tatjana N. Zhilnikova

2017-01-01

Full Text Available Abstract. Objectives The aim of the study is to clarify the dependence of the cement stone strength on additional porosity that is formed owing both to the cement stone’s development of free deformations and the expansion of the hardening concrete in the second stage as caused by the action of the expanding additive. Method The study is based on the introduction of a sulphoaluminate-type expanding additive in the composition of a binder based on alumina cement, natural gypsum stone and nitrilotrimethylphosphonic acid. Results It is shown that an important role is played in the technology of expanding concrete not only by the degree of expansion of the cement stone, but also by its strength, both during the development of deformations and following stabilisation. Among factors influencing the kinetics of hardening are not only recipe-related (composition and dosage of the additive, mineralogical composition of Portland cement clinker, composition of the concrete, presence of chemical additives, but also technological (fineness of cement grinding, hardening temperature, etc. that makes the management of the processes of structure formation quite complex. The dependence of the strength of cement stone on the additional porosity formed due to the growth of the cement stone own free deformations and expansion of the hardening concrete in the second stage due to the action of the expanding additive is revealed; dependence of the influence of kinetics of the structure formation regulator - nitrilotrimethylphosphonic acid - on the consistency of the development of the intrinsic free expansion deformations and the formation of the strength of the cement stone in the second stage; the dependence of the strength of the cement stone on the additional porosity formed due to gas evolution and expansion of the mixture in the first stage due to the action of the gas-forming additive; the influence of the constraint of expansion on the formation of the

A Combined Precipitation, Yield Stress, and Work Hardening Model for Al-Mg-Si Alloys Incorporating the Effects of Strain Rate and Temperature

Science.gov (United States)

Myhr, Ole Runar; Hopperstad, Odd Sture; Børvik, Tore

2018-05-01

In this study, a combined precipitation, yield strength, and work hardening model for Al-Mg-Si alloys known as NaMo has been further developed to include the effects of strain rate and temperature on the resulting stress-strain behavior. The extension of the model is based on a comprehensive experimental database, where thermomechanical data for three different Al-Mg-Si alloys are available. In the tests, the temperature was varied between 20 °C and 350 °C with strain rates ranging from 10-6 to 750 s-1 using ordinary tension tests for low strain rates and a split-Hopkinson tension bar system for high strain rates, respectively. This large span in temperatures and strain rates covers a broad range of industrial relevant problems from creep to impact loading. Based on the experimental data, a procedure for calibrating the different physical parameters of the model has been developed, starting with the simplest case of a stable precipitate structure and small plastic strains, from which basic kinetic data for obstacle limited dislocation glide were extracted. For larger strains, when work hardening becomes significant, the dynamic recovery was linked to the Zener-Hollomon parameter, again using a stable precipitate structure as a basis for calibration. Finally, the complex situation of concurrent work hardening and dynamic evolution of the precipitate structure was analyzed using a stepwise numerical solution algorithm where parameters representing the instantaneous state of the structure were used to calculate the corresponding instantaneous yield strength and work hardening rate. The model was demonstrated to exhibit a high degree of predictive power as documented by a good agreement between predictions and measurements, and it is deemed well suited for simulations of thermomechanical processing of Al-Mg-Si alloys where plastic deformation is carried out at various strain rates and temperatures.

PRECIPITATION HARDENING IN B2-ORDERED NiAl BY Ni2AlTiCOMPOUND

Institute of Scientific and Technical Information of China (English)

W.H. Tian; K. Ohishi; M. Nemoto

2001-01-01

Microstructural variations and correlated hardness changes in B2-ordered NiAl containing fine precipitation of Ni2AlTi have been investigated by means of transmission electron microscopy (TEM) and hardness tests. The amount of age hardening is not large as compared to the large microstructural variations during aging. TEM observations have revealed that the L21-type Ni2AlTi precipitates keep a lattice coherency with the NiAl matrix at the beginning of aging. By longer periods of aging Ni2AlTi precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. The temperature dependence of the yield strength of precipitate-containing B2-ordered NiAl was investigated by compression tests over the temperature range of 873-1273K. The fine precipitation of Ni2AlTi was found to enhance greatly the yield strength and the high-temperature strength is comparison with that of superalloy Mar-M200.``

Mechanically activated fly ash as a high performance binder for civil engineering

International Nuclear Information System (INIS)

Rieger, D; Kullová, L; Čekalová, M; Novotný, P; Pola, M

2017-01-01

This study is aimed for investigation of fly ash binder with suitable properties for civil engineering needs. The fly ash from Czech brown coal power plant Prunerov II was used and mechanically activated to achieve suitable particle size for alkaline activation of hardening process. This process is driven by dissolution of aluminosilicate content of fly ash and by subsequent development of inorganic polymeric network called geopolymer. Hardening kinetics at 25 and 30 °C were measured by strain controlled small amplitude oscillatory rheometry with strain of 0.01 % and microstructure of hardened binder was evaluated by scanning electron microscopy. Strength development of hardened binder was investigated according to compressional and flexural strength for a period of 180 days. Our investigation finds out, that mechanically activated fly ash can be comparable to metakaolin geopolymers, according to setting time and mechanical parameters even at room temperature curing. Moreover, on the bases of long time strength development, achieved compressional strength of 134.5 after 180 days is comparable to performance of high grade Portland cement concretes. (paper)

Phenomenological Analysis of the Kinematic Hardening of HSLA and IF Steels Using Reverse Simple Shear Tests

International Nuclear Information System (INIS)

Aouafi, A.; Bouvier, S.; Gasperini, M.; Lemoine, X.; Bouaziz, O.

2007-01-01

Reverse simple shear tests are used to analyse the Bauschinger effect and the evolution of the kinematic hardening for a wide range of equivalent von Mises strain [0.025 - 0.3]. This work is carried out on two high strength low-alloyed steels. In order to investigate the effect of the precipitates on the macroscopic behaviour, a ferritic mild steel is used as a reference. Different phenomenological descriptions of the back-stress tensor are examined in order to analyse their ability to describe the experimental behaviour

The Prediction of the Mechanical Properties for Dual-Phase High Strength Steel Grades Based on Microstructure Characteristics

Directory of Open Access Journals (Sweden)

Emil Evin

2018-04-01

Full Text Available The decrease of emissions from vehicle operation is connected mainly to the reduction of the car’s body weight. The high strength and good formability of the dual phase steel grades predetermine these to be used in the structural parts of the car’s body safety zones. The plastic properties of dual phase steel grades are determined by the ferrite matrix while the strength properties are improved by the volume and distribution of martensite. The aim of this paper is to describe the relationship between the mechanical properties and the parameters of structure and substructure. The heat treatment of low carbon steel X60, low alloyed steel S460MC, and dual phase steel DP600 allowed for them to reach states with a wide range of volume fractions of secondary phases and grain size. The mechanical properties were identified by a tensile test, volume fraction of secondary phases, and grain size were measured by image analysis. It was found that by increasing the annealing temperature, the volume fraction of the secondary phase increased, and the ferrite grains were refined. Regression analysis was used to find out the equations for predicting mechanical properties based on the volume fraction of the secondary phase and grain size, following the annealing temperature. The hardening mechanism of the dual phase steel grades for the states they reached was described by the relationship between the strain-hardening exponent and the density of dislocations. This allows for the designing of dual phase steel grades that are “tailored” to the needs of the automotive industry customers.

Temperature Effects on the Tensile Properties of Precipitation-Hardened Al-Mg-Cu-Si Alloys

Directory of Open Access Journals (Sweden)

J.B. Ferguson

2016-02-01

Full Text Available Because the mechanical performance of precipitation-hardened alloys can be significantly altered with temperature changes, understanding and predicting the effects of temperatures on various mechanical properties for these alloys are important. In the present work, an analytical model has been developed to predict the elastic modulus, the yield stress, the failure stress, and the failure strain taking into consideration the effect of temperatures for precipitation-hardenable Al-Mg-Cu-Si Alloys (Al-A319 alloys. In addition, other important mechanical properties of Al-A319 alloys including the strain hardening exponent, the strength coefficient, and the ductility parameter can be estimated using the current model. It is demonstrated that the prediction results based on the proposed model are in good agreement with those obtained experimentally in Al-A319 alloys in the as-cast condition and after W and T7 heat treatments.

Comparison of Thermal Stability of Dry High-strength Concrete and Wet High-strength Concrete

Science.gov (United States)

Musorina, Tatiana; Katcay, Aleksandr; Selezneva, Anna; Kamskov, Victor

2018-03-01

High-strength concrete is a modern material, which occupies it`s own niche on the construction material market. It is applicable in a large-scale high-rise construction, particularly an underground construction is a frequently used solution for a space saving. Usually underground structure is related to a wet usage environment. Though not all properties of the high-strength concrete are investigated to the full extent. Under adverse climatic conditions of the Russian Federation one of the most important properties for constructional materials is a thermal capacity. Therefore, the main purpose of the paper is to compare a thermal capacity of the high-strength concrete in humid conditions and a thermal capacity of the high-strength concrete in dry operational condition. During the study dependency between thermal capacity and design wall thickness and ambient humidity has to be proven with two experiments. As a result the theoretical relation between thermal capacity characteristic - thermal inertia and wall thickness and ambient humidity was confirmed by the experimental data. The thermal capacity of a building is in direct ratio to the construction thickness. It follows from the experiments and calculations that wet high-strength concrete has less thermal stability.

Analysis of the work-hardening process in spheroidized steels

International Nuclear Information System (INIS)

Pacheco, J.L.

1981-07-01

An elementary model for the work-hardening process in duplex-structures steels (ferrite - spheroidite) is proposed and tested on low, medium and high carbon content, which seems to give good results concerning the influence of the volume fraction and particle size of the second phase on the work-hardening behaviour. (Author) [pt

[Microstructural changes in hardened beans (Phaseolus vulgaris)].

Science.gov (United States)

Mujica, Maria Virginia; Granito, Marisela; Soto, Naudy

2015-06-01

(Phaseolus vulgaris). The hardening of Phaseolus vulgaris beans stored at high temperature and high relative humidity is one of the main constraints for consumption. The objective of this research was to evaluate by scanning electron microscopy, structural changes in cotyledons and testa of the hardened beans. The freshly harvested grains were stored for twelve months under two conditions: 5 ° C-34% RH and 37 ° C-75% RH, in order to promote hardening. The stored raw and cooked grains were lyophilized and fractured. The sections of testa and cotyledons were observed in an electron microscope JSM-6390. After twelve months, grains stored at 37 ° C-75% RH increased their hardness by 503%, whereas there were no significant changes in grains stored at 5 ° C-34% RH. At the microstructural level, the cotyledons of the raw grains show clear differences in appearance of the cell wall, into the intercellular space size and texture matrix protein. There were also differences in compaction of palisade and sub-epidermal layer in the testa of raw grains. After cooking, cotyledon cells of the soft grains were well separated while these ofhard grains were seldom separated. In conclusion, the found differences in hard and soft grains showed a significant participation of both structures, cotyledons and testa, in the grains hardening.

Unit rupture work as a criterion for quantitative estimation of hardenability in steel

International Nuclear Information System (INIS)

Kramarov, M.A.; Orlov, E.D.; Rybakov, A.B.

1980-01-01

Shown is possible utilization of high sensitivity of resistance to fracture of structural steel to the hardenability degree in the course of hardening to find the quantitative estimation of the latter one. Proposed is a criterion kappa, the ratio of the unit rupture work in the case of incomplete hardenability (asub(Tsub(ih))) under investigation, and the analoguc value obtained in the case of complete hardenability Asub(Tsub(Ch)) at the testing temperature corresponding to the critical temperature Tsub(100(M). Confirmed is high criterion sensitivity of the hardened steel structure on the basis of experimental investigation of the 40Kh, 38KhNM and 38KhNMFA steels after isothermal hold-up at different temperatures, corresponding to production of various products of austenite decomposition

Equipment and Protocols for Quasi-Static and Dynamic Tests of Very-High-Strength Concrete (VHSC) and High-Strength High-Ductility Concrete (HSHDC)

Science.gov (United States)

2016-08-01

Concrete (VHSC) and High-Strength High-Ductility Concrete (HSHDC) En gi ne er R es ea rc h an d D ev el op m en t Ce nt er Brett A...Very-High-Strength Concrete (VHSC) and High-Strength High-Ductility Concrete (HSHDC) Brett A. Williams, Robert D. Moser, William F. Heard, Carol F...equipment and protocols for tests of both very-high-strength concrete (VHSC) and high- strength high-ductility concrete (HSHDC) to predict blast

Microstructural evolution and mechanical properties of a novel FeCrNiBSi advanced high-strength steel: Slow, accelerated and fast casting cooling rates

Energy Technology Data Exchange (ETDEWEB)

Askari-Paykani, Mohsen; Shahverdi, Hamid Reza, E-mail: shahverdi@modares.ac.ir; Miresmaeili, Reza

2016-06-21

In the current work, three different solidification routes and a two-step heat treatment process were applied to a novel FeCrNiBSi alloy system to introduce a new candidate for advanced high-strength steels. The evolution of the microstructure after solidification, heat treatment, and tensile deformation was characterized using optical and electron microscopy techniques, as well as hardness and room temperature uniaxial tensile tests. The effects of the different solidification routes and heat treatment parameters on the deformation and fracture mechanisms of this steel are discussed. Grain refinement, precipitation hardening, and solid solution as a result of the fast casting cooling rate led to an increase in strength at improved ductility. This result can be explained partly by the less severe stress/strain partitioning at the matrix grain/M{sub 2}B interfaces and better interface cohesion. Moreover, the stress/strain partitioning characteristics between the matrix grains and M{sub 2}B led to a higher initial strain hardening rate. The fast casting cooling rate further promoted ductile fracture mechanisms, which is a result of increased cleavage fracture stress. The higher casting cooling rate and two-step heat treatment resulted in a strong increase in formability index, from 8 GPa% to 24 GPa%, at which the mechanical properties occupy the TRIP envelope. Heat treatment of the fast-cooling specimens led to a small reduction in yield and tensile strength and 22% total elongation percentage improvement (from 10% to 32%).

Influence of Eco-Friendly Mineral Additives on Early Age Compressive Strength and Temperature Development of High-Performance Concrete

Science.gov (United States)

Kaszynska, Maria; Skibicki, Szymon

2017-12-01

High-performance concrete (HPC) which contains increased amount of both higher grade cement and pozzolanic additives generates more hydration heat than the ordinary concrete. Prolonged periods of elevated temperature influence the rate of hydration process in result affecting the development of early-age strength and subsequent mechanical properties. The purpose of the presented research is to determine the relationship between the kinetics of the heat generation process and the compressive strength of early-age high performance concrete. All mixes were based on the Portland Cement CEM I 52.5 with between 7.5% to 15% of the cement mass replaced by the silica fume or metakaolin. Two characteristic for HPC water/binder ratios of w/b = 0.2 and w/b = 0.3 were chosen. A superplasticizer was used to maintain a 20-50 mm slump. Compressive strength was determined at 8h, 24h, 3, 7 and 28 days on 10x10x10 cm specimens that were cured in a calorimeter in a constant temperature of T = 20°C. The temperature inside the concrete was monitored continuously for 7 days. The study determined that the early-age strength (t<24h) of concrete with reactive mineral additives is lower than concrete without them. This is clearly visible for concretes with metakaolin which had the lowest compressive strength in early stages of hardening. The amount of the superplasticizer significantly influenced the early-age compressive strength of concrete. Concretes with additives reached the maximum temperature later than the concretes without them.

High strength alloys

Science.gov (United States)

Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

2010-08-31

High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

Novel circuits for radiation hardened memories

International Nuclear Information System (INIS)

Haraszti, T.P.; Mento, R.P.; Moyer, N.E.; Grant, W.M.

1992-01-01

This paper reports on implementation of large storage semiconductor memories which combine radiation hardness with high packing density, operational speed, and low power dissipation and require both hardened circuit and hardened process technologies. Novel circuits, including orthogonal shuffle type of write-read arrays, error correction by weighted bidirectional codes and associative iterative repair circuits, are proposed for significant improvements of SRAMs' immunity against the effects of total dose and cosmic particle impacts. The implementation of the proposed circuit resulted in fault-tolerant 40-Mbit and 10-Mbit monolithic memories featuring a data rate of 120 MHz and power dissipation of 880 mW. These experimental serial-parallel memories were fabricated with a nonhardened standard CMOS processing technology, yet provided a total dose hardness of 1 Mrad and a projected SEU rate of 1 x 10 - 12 error/bit/day. Using radiation hardened processing improvements by factors of 10 to 100 are predicted in both total dose hardness and SEU rate

Effect of resin composition to the electrical and mechanical properties of high voltage insulator material

International Nuclear Information System (INIS)

Totok Dermawan; Elin Nuraini; Suyamto

2012-01-01

A solid insulator manufacture of resins for high voltage with a variation of resin and hardener composition has been made. The purpose of research to know electrical and mechanical properties of high voltage insulator material of resin. To determine its electric properties, the material is tested its breakdown voltage and the flashover voltage that occurred on the surface. While to determine the mechanical properties were tested by measuring its strength with a tensile test. From testing with variety of mixed composition it is known that for composition between hardener and resin of 1 : 800 has most advantageous properties because it has good strength with a tensile strength of 19.86 MPa and enough high dielectric strength of 43.2 kV / mm). (author)

Interaction between α-calcium sulfate hemihydrate and superplasticizer from the point of adsorption characteristics, hydration and hardening process

International Nuclear Information System (INIS)

Guan Baohong; Ye Qingqing; Zhang Jiali; Lou Wenbin; Wu Zhongbiao

2010-01-01

Superplasticizers (SPs), namely sulfonated melamine formaldehyde (SMF) and polycarboxylate (PC), were independently admixed with α-calcium sulfate hemihydrate based plaster to improve the material's performance. SMF and PC gave, respectively, 38% and 25% increases in the 2 h bending strength at the optimum dosages of 0.5 wt.% and 0.3 wt.%, which are determined essentially by the maximum water-reducing efficiency. The peak shift of binding energy of Ca2p 3/2 detected by X-ray photoelectron spectroscopy (XPS) suggests that SPs are chemically adsorbed on gypsum surface. A careful examination of the strength development of set plaster allowed the hydration and hardening process to be divided roughly into five stages. SMF accelerates early hydration, while PC decelerates it. Both SPs allowed similar maximum water reductions, giving a more compact structure and a decrease in total pore volume and average pore diameter, and thus leading to higher strengths in the hardened plasters with SPs.

Surface hardening of 30CrMnSiA steel using continuous electron beam

Science.gov (United States)

Fu, Yulei; Hu, Jing; Shen, Xianfeng; Wang, Yingying; Zhao, Wansheng

2017-11-01

30CrMnSiA high strength low alloy (HSLA) carbon structural steel is typically applied in equipment manufacturing and aerospace industries. In this work, the effects of continuous electron beam treatment on the surface hardening and microstructure modifications of 30CrMnSiA are investigated experimentally via a multi-purpose electron beam machine Pro-beam system. Micro hardness value in the electron beam treated area shows a double to triple increase, from 208 HV0.2 on the base metal to 520 HV0.2 on the irradiated area, while the surface roughness is relatively unchanged. Surface hardening parameters and mechanisms are clarified by investigation of the microstructural modification and the phase transformation both pre and post irradiation. The base metal is composed of ferrite and troostite. After continuous electron beam irradiation, the micro structure of the electron beam hardened area is composed of acicular lower bainite, feathered upper bainite and part of lath martensite. The optimal input energy density for 30CrMnSiA steel in this study is of 2.5 kJ/cm2 to attain the proper hardened depth and peak hardness without the surface quality deterioration. When the input irradiation energy exceeds 2.5 kJ/cm2 the convective mixing of the melted zone will become dominant. In the area with convective mixing, the cooling rate is relatively lower, thus the micro hardness is lower. The surface quality will deteriorate. Chemical composition and surface roughness pre and post electron beam treatment are also compared. The technology discussed give a picture of the potential of electron beam surface treatment for improving service life and reliability of the 30CrMnSiA steel.

MICROSTRUCTURAL FEATURES EVALUATION OF AGE-HARDENED A 226 CAST ALLOY BY IMAGE ANALYSIS

Directory of Open Access Journals (Sweden)

Lenka Kuchariková

2018-01-01

Full Text Available Age-hardening provides one of the most widely used mechanisms for the strengthening of aluminum alloys. The age-hardening involves three steps: solution treatment, quenching and aging. The temperature of solution treatment and aging is very important in order to reach desired properties of castings. The optimum temperature of solution treatment and aging led to formation microstructural features in form which does not lead to decreasing properties, but increasing ones. The major microstructural features in A 226 cast alloys which are responsible for increasing properties are: eutectic Si particles, Cu-rich phases, Fe-rich phases and porosity. The increase of properties depends on morphology, size and volume of microstructural features. In order to assess age-hardening influence on microstructural features in A226 cast alloys were used as possibilities of evaluation by means of image analysis. Quantitative analysis decelerate changes in microstructure includes the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe-rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al2Cu further increase in the hardness and tensile strength in the alloy. Changes of mechanical properties were measured in line with STN EN ISO.

METHYL JASMONATE AND STEM BENDING HARDENING AND INITIAL GROWTH OF Cordia trichotoma SEEDLINGS

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Danielle Acco Cadorin

2015-12-01

Full Text Available The submission of seedlings to mechanical stimuli and plant growth regulator promote their hardening and can be included in the routine of nurseries, favoring the survival and initial growth in the field. The study aimed to evaluate the effects of applying methyl jasmonate and stem bending in hardening and initial growth of Cordia trichotoma seedlings. Seedlings were subjected to 20 stem bending daily for 4 weeks; 20 stem bending daily for 8 weeks; 50 µmol.L-1 of methyl jasmonate applied weekly for 4 weeks; 50 µmol.L-1 of methyl jasmonate applied weekly for 8 weeks and the control treatment. The design was a completely randomized, with five repetitions of the fourteen seedlings. Seedlings submitted to hardening treatments showed less increment in height, greater increment in stem diameter and less value for strength index. Seedlings of control treatment had greater loss of root tissue electrolytes and less potential for root regeneration. In the field, 180 days after planting, seedlings submitted to eight weeks of stem bending and eight methyl jasmonate applications showed greater increment in height and stem diameter. The results indicate that both stem bending such as methyl jasmonate application for eight weeks are effective in promoting hardening and improve the starting performance in field of Cordia trichotoma seedlings.

Precipitation hardening in dilute Al–Zr alloys

Directory of Open Access Journals (Sweden)

Pedro Henrique Lamarão Souza

2018-01-01

Full Text Available The aim of this study was to investigate the effect of solute content (hipoperitectic Al–0.22 wt.%Zr and hiperperitectic Al–0.32 wt.%Zr on the precipitation hardening and microstructural evolution of dilute Al–Zr alloys isothermally aged. The materials were conventionally cast in a muffle furnace, solidified in a water-cooled Cu mold and subsequently heat-treated at the temperature of 650 K (377 °C for 4, 12, 24, 100 and 400 h. Mechanical characterization was performed at room temperature, using a microhardness tester and microstructural characterization was carried out on a Transmission Electron Microscope – TEM. The observed microhardness values increased during isothermal aging, due to the precipitation of nanometer-scale Al3Zr L12 particles. Peak strength was achieved within 100 h of aging. After aging for 400 h, microhardness values presented a slight decrease for both alloys, thus indicating overaging due to the coalescence of precipitates. Microhardness values increased with solute content, due to the precipitation of a higher number density of finer precipitates. After 400 h of heat-treating, coalescence was higher for the alloy with lower solute content and, also, the presence of antiphase boundaries – APBs, planar faults associated with the L12 to D023 structural transition, were observed. Comparing theoretical calculations of the increment in strength due to precipitation strengthening with experimental results, it was observed that their values are in reasonable agreement. The Orowan dislocation looping mechanism takes place during precipitation hardening for both alloys in the peak hardness condition.

High tensile strength fly ash based geopolymer composite using copper coated micro steel fiber

DEFF Research Database (Denmark)

Ranjbar, Navid; Mehrali, Mehdi; Mehrali, Mohammad

2016-01-01

-matrix interaction. In this present study, effects of micro steel fibers (MSF) incorporation on mechanical properties of fly ash based geopolymer was investigated at different volume ratio of matrix. Various properties of the composite were compared in terms of fresh state by flow measurement and hardened state......As a ceramic-like material, geopolymers show a high quasi-brittle behavior and relatively low fracture energy. To overcome this, the addition of fibers to a brittle matrix is a well-known method to improve the flexural strength. Moreover, the success of the reinforcements is dependent on the fiber...... by variation of shrinkage over time to assess performance of the composites subjected to flexural and compressive load. The fiber-matrix interface, fiber surface and toughening mechanisms were assessed using field emission scan electron microscopy (FESEM) and atomic force microscopy (AFM) through a period...

Effect of Lime Powder and Metakaolin on Fresh and Hardened Properties of Self Compacting Concrete

Directory of Open Access Journals (Sweden)

Rizwan Ahmad Khan

2016-12-01

Full Text Available This study investigated the fresh and hardened properties of Self-Compacting Concrete (SCC with different types and amounts of admixtures. Six mixes were prepared by replacing 30% of cement with different percentages of fly ash (FA, lime powder (LP and metakaolin (MK. Water- Cement ratio was kept constant at 0.41 and superplasticizer dosage of 1% by weight of cement. The filling and passing ability were investigated through Slump Flow, J-Ring, V-funnel and L-box test before filling the moulds. The compressive strength of hardened SCC cubes was also measured after specified days of curing (7, 14, 28, 60 & 90 days. The workability test results showed that as FA was replaced by increasing percentages of LP and MK, the mixes became dense and hence less workable. It was observed that the compressive strength showed an increase with increasing percentage replacement of FA with LP and MK. This increase was higher for mixes with MK than that of mixes with LP.

Influence of Temperature on Mechanical Behavior During Static Restore Processes of Al-Zn-Mg-Cu High Strength Aluminum Alloy

Directory of Open Access Journals (Sweden)

ZHANG Kun

2017-06-01

Full Text Available Flow stress behaviors of as-cast Al-Zn-Mg-Cu high strength aluminum alloy during static restore processes were investigated by: Isothermal double-pass compression tests at temperatures of 300-400℃, strain rates of 0.01-1 s-1, strains of 33% +20% with the holding times of 0~900 s after the first pass compression. The results indicate that the deformation temperature has a dramatical effect on mechanical behaviors during static restore processes of the alloy. (1 At 300 ℃ and 330 ℃ lower temperatures, the recovery during the deformation is slow, and deformation energy stored in matrix is higher, flow stresses at the second pass deformation decreased during the recovery and recrystallization, and the stress softening phenomena is observed. Stress softening is increased with the increasing holding time; Precipitation during the holding time inhibites the stress softening. (2 At 360 ℃ and 400 ℃ higher temperatures, the recovery during deformation is rapid, and deformation energy stored in matrix is lower. Solid solubility is higher after holding, so that flow stress at the second pass deformation is increased, stress hardening phenomena is observed. Stress hardening decreased with the increasing holding time duo to the recovery and recrystallization during holding period at 360 ℃; Precipitation during holding also inhibited the stress softening. However, Stress hardening remains constant with the increasing holding time duo to the reasanenal there are no recovery and recrystallization during holding period at 400 ℃.

Scintillation-Hardened GPS Receiver

Science.gov (United States)

Stephens, Donald R.

2015-01-01

CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

Boundary and sub-boundary hardening in tempered martensitic 9Cr steel during long-term creep at 650 C

Energy Technology Data Exchange (ETDEWEB)

Abe, Fujio [National Institute for Materials Science, Sengen, Tsukuba (Japan)

2010-07-01

The boundary and sub-boundary hardening is shown to be the most important strengthening mechanism in creep of the 9% Cr steel base metal and welded joints. The addition of boron reduces the coarsening rate of M{sub 23}C{sub 6} carbides along boundaries near prior austenite grain boundaries during creep, enhancing the boundary and sub-boundary hardening. This improves long-term creep strength of base metal. The enhancement of boundary and sub-boundary hardening is significantly reduced in fine-grained region of Ac{sub 3} HAZ simulated specimens of conventional steel P92. In NIMS 9Cr boron steel welded joints, the grain size and distribution of carbonitrides are substantially the same between the HAZ and base metal, where fine carbonitrides are distributed along the lath and block boundaries as well as along prior austenite grain boundaries. This is essential for the suppression of Type IV fracture in NIMS 9% Cr boron steel welded joints. Newly alloy-designed 9Cr steel with 160 ppm boron and 85 ppm nitrogen exhibits much higher creep rupture strength of base metal than P92 and also no Tpe-IV fracture in welded joints at 650 C. (orig.)

Age hardening in die-cast Mg–Al–RE alloys due to minor Mn additions

Energy Technology Data Exchange (ETDEWEB)

Zhu, S.M., E-mail: suming.zhu@rmit.edu.au [School Engineering, RMIT University, Carlton, Victoria 3053 (Australia); Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); Abbott, T.B. [School Engineering, RMIT University, Carlton, Victoria 3053 (Australia); Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); Magontec Limited, Sydney, New South Wales 2000 (Australia); Gibson, M.A. [School Engineering, RMIT University, Carlton, Victoria 3053 (Australia); Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); CSIRO Manufacturing Flagship, Clayton, Victoria 3168 (Australia); Nie, J.F. [Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); Easton, M.A. [School Engineering, RMIT University, Carlton, Victoria 3053 (Australia)

2016-02-22

Die-cast Mg–Al–rare earth (RE) alloys are normally used in the as-cast condition without the application of heat treatment because it is a common perception that heat treatment will not provide benefit to these alloys. This paper reports, for the first time, that enhanced age hardenability can be achieved in die-cast Mg–Al–RE alloys with minor Mn additions. For example, the yield strength of Mg–4 wt%Al–3 wt%La alloy with 0.32 wt% Mn is increased by ∼34 MPa (∼26%) after ageing at 200 °C for 32 h (T5). The enhanced age hardenability is associated with the precipitation of nanoscale Al–Mn particles during ageing.

High strength ferritic alloy

International Nuclear Information System (INIS)

1977-01-01

A high strength ferritic steel is specified in which the major alloying elements are chromium and molybdenum, with smaller quantities of niobium, vanadium, silicon, manganese and carbon. The maximum swelling is specified for various irradiation conditions. Rupture strength is also specified. (U.K.)

The capability of pulsed laser radiation for cutting band saws hardening

Directory of Open Access Journals (Sweden)

Marinin Evgeny

2017-01-01

Full Text Available The article deals with the possibilities of pulsed laser radiation for hardening the band saws. The regimes of pulsed laser hardening the band saws of 1 mm thick made of tool steel 9CrV are grounded theoretically and experimentally tested. Selected and justified modes of treatment harden in the autohardening mode without additional heat removal. The results of the experimental research of microhardness are presented and formed as a result of processing of the microstructure. Selected modes increase the microhardness of the surface to 8500 MPa and form ultra highly dispersed structure in the surface layer characterized by high resistance to abrasion.

Radiation hardening of integrated circuits technologies

International Nuclear Information System (INIS)

Auberton-Herve, A.J.; Leray, J.L.

1991-01-01

The radiation hardening studies started in the mid decade -1960-1970. To survive the different military or space radiative environment, a new engineering science borned, to understand the degradation of electronics components. The different solutions to improve the electronic behavior in such environment, have been named radiation hardening of the technologies. Improvement of existing technologies, and qualification method have been widely studied. However, at the other hand, specific technologies was developped : The Silicon On Insulator technologies for CMOS or Bipolar. The HSOI3HD technology (supported by DGA-CEA DAM and LETI with THOMSON TMS) offers today the highest hardening level for the integration density of hundreds of thousand transistors on the same silicon. Full complex systems would be realized on a single die with a technological radiation hardening and no more system hardening

Radiation hardened high efficiency silicon space solar cell

International Nuclear Information System (INIS)

Garboushian, V.; Yoon, S.; Turner, J.

1993-01-01

A silicon solar cell with AMO 19% Beginning of Life (BOL) efficiency is reported. The cell has demonstrated equal or better radiation resistance when compared to conventional silicon space solar cells. Conventional silicon space solar cell performance is generally ∼ 14% at BOL. The Radiation Hardened High Efficiency Silicon (RHHES) cell is thinned for high specific power (watts/kilogram). The RHHES space cell provides compatibility with automatic surface mounting technology. The cells can be easily combined to provide desired power levels and voltages. The RHHES space cell is more resistant to mechanical damage due to micrometeorites. Micro-meteorites which impinge upon conventional cells can crack the cell which, in turn, may cause string failure. The RHHES, operating in the same environment, can continue to function with a similar crack. The RHHES cell allows for very efficient thermal management which is essential for space cells generating higher specific power levels. The cell eliminates the need for electrical insulation layers which would otherwise increase the thermal resistance for conventional space panels. The RHHES cell can be applied to a space concentrator panel system without abandoning any of the attributes discussed. The power handling capability of the RHHES cell is approximately five times more than conventional space concentrator solar cells

Working hardening modelization in zirconium alloys

International Nuclear Information System (INIS)

Sanchez, P.; Pochettino, Alberto A.

1999-01-01

Working hardening effects on mechanical properties and crystallographic textures formation in Zr-based alloys are studied. The hardening mechanisms for different grain deformations and topological conditions of simple crystal yield are considered. Results obtained show that the differences in the cold rolling textures (L and T textures) can be related with hardening microstructural parameters. (author)

Practical aspects of systems hardening

International Nuclear Information System (INIS)

Shepherd, W.J.

1989-01-01

Applications of hardening technology in a practical system require a balance between the factors governing affordability, producibility, and survivability of the finished design. Without careful consideration of the top-level system operating constraints, a design engineer may find himself with a survivable but overweight, unproductive, expensive design. This paper explores some lessons learned in applying hardening techniques to several laser communications programs and is intended as an introductory guide to novice designers faced with the task of hardening a space system

Effect of aging and cold working on the high-temperature low-cycle fatigue behavior of alloy 800H. Part I. The effect of hardening processes on the initial stress--strain curve

International Nuclear Information System (INIS)

Villagrana, R.E.; Kaae, J.L.; Ellis, J.R.; Gantzel, P.K.

1978-01-01

The individual and combined effects of cold working (5 and 10%) and aging (4000 and 8000 h at 538 to 760 0 C) on the microstructure and high-temperature yield strength of alloy 800H have been investigated. The specimens were tested at the aging temperatures. During testing some of the specimens showed the phenomenon of serrated yielding. In order of importance, the principal hardening agents observed in this work were: cold work, the precipitation of Cr 23 C 6 at the grain boundaries, and, in some cases, the precipitation of a Perovskite-type γ' phase in the grain interiors

Properties of high-workability concrete with recycled concrete aggregate

OpenAIRE

Safiuddin,; Alengaram,Ubagaram Johnson; Salam,Abdus; Jumaat,Mohd Zamin; Jaafar,Fahrol Fadhli; Saad,Hawa Binti

2011-01-01

This study presents the effects of recycled concrete aggregate (RCA) on the key fresh and hardened properties of concrete. RCA was used to produce high-workability concrete substituting 0-100% natural coarse aggregate (NCA) by weight. The slump and slump flow of fresh concretes were determined to ensure high workability. In addition, the compressive, flexural and splitting tensile strengths, modulus of elasticity, and permeable voids of hardened concretes were determined. The test results rev...

Material Selection for an Ultra High Strength Steel Component Based on the Failure Criteria of CrachFEM

International Nuclear Information System (INIS)

Kessler, L.; Beier, Th.; Werner, H.; Horstkott, D.; Dell, H.; Gese, H.

2005-01-01

An increasing use of combining more than one process step is noticed for coupling crash simulations with the results of forming operations -- mostly by inheriting the forming history like plastic strain and material hardening. Introducing a continuous failure model allows a further benefit of these coupling processes; it sometimes can even be the most attractive result of such a work. In this paper the algorithm CrachFEM for fracture prediction has been used to generate more benefit of the successive forming and crash simulations -- especially for ultra high strength steels. The choice and selection of the material grade in combination with the component design can therefore be done far before the prototyping might show an unsuccessful crash result; and in an industrial applicable manner

Hardening parts by chrome plating in manufacture and repair

Science.gov (United States)

Astanin, V. K.; Pukhov, E. V.; Stekolnikov, Y. A.; Emtsev, V. V.; Golikova, O. A.

2018-03-01

In the engineering industry, galvanic coatings are widely used to prolong the service life of the machines, which contribute to the increase in the strength of the parts and their resistance to environmental influences, temperature and pressure drops, wear and fretting corrosion. Galvanic coatings have been widely applied in engineering, including agriculture, aircraft building, mining, construction, and electronics. The article focuses on the manufacturing methods of new agricultural machinery parts and the repair techniques of worn parts by chrome plating. The main attention is paid to the unstable methods of chromium deposition (in pulsed and reversing modes) in low-concentration electrolytes, which makes it possible to increase the reliability and durability of the hardened parts operation by changing the conditions of electrocrystallization, that is, directed formation of the structure and texture, thickness, roughness and microhardness of chromium plating. The practical recommendations are given on the current and temperature regimes of chromium deposition and composition of baths used for the restoration and hardening of the machine parts. Moreover, the basic methods of machining allowances removal are analysed.

Thermophysical and Mechanical Properties of Hardened Cement Paste with Microencapsulated Phase Change Materials for Energy Storage.

Science.gov (United States)

Cui, Hongzhi; Liao, Wenyu; Memon, Shazim Ali; Dong, Biqin; Tang, Waiching

2014-12-16

In this research, structural-functional integrated cement-based materials were prepared by employing cement paste and a microencapsulated phase change material (MPCM) manufactured using urea-formaldehyde resin as the shell and paraffin as the core material. The encapsulation ratio of the MPCM could reach up to 91.21 wt%. Thermal energy storage cement pastes (TESCPs) incorporated with different MPCM contents (5%, 10%, 15%, 20% and 25% by weight of cement) were developed, and their thermal and mechanical properties were studied. The results showed that the total energy storage capacity of the hardened cement specimens with MPCM increased by up to 3.9-times compared with that of the control cement paste. The thermal conductivity at different temperature levels (35-36 °C, 55-56 °C and 72-74 °C) decreased with the increase of MPCM content, and the decrease was the highest when the temperature level was 55-56 °C. Moreover, the compressive strength, flexural strength and density of hardened cement paste decreased with the increase in MPCM content linearly. Among the evaluated properties, the compressive strength of TESCPs had a larger and faster degradation with the increase of MPCM content.

Microstructural evolution and hardening of GH3535 alloy under energetic Xe ion irradiation at room temperature and 650 °C

Science.gov (United States)

Huang, Hefei; Gao, Jie; Radiguet, Bertrand; Liu, Renduo; Li, Jianjian; Lei, Guanhong; Huang, Qing; Liu, Min; Xie, Ruobing

2018-02-01

The GH3535 alloy was irradiated with 7 MeV Xe26+ ions to a dose of 10 dpa at room temperature (RT) and 650 °C, and subsequently examined using Transmission Electron Microscopy (TEM) and nanoindentation. High numbers of nano-sized black dots, identified as dislocation loops were observed in both irradiated samples. The dislocation loops detected at the high temperature irradiated sample (size/number density: 9.5 nm/1.9 × 1021 m-3) were found to be larger in size but less in amount as compared to that of the case of RT irradiation (6.9 nm/18.7 × 1021 m-3). In addition, the large-sized Mo-Cr rich precipitates (16.4 nm/3.7 × 1021 m-3) were observed in the sample irradiated at 650 °C. Moreover, the Xe bubbles, with smaller size (2.9 nm) but higher number density (77.8 × 1021 m-3) among the irradiated induced defects, were also detected in the case of high temperature irradiated sample via the diffusion and aggregation of Xe atoms. Nanoindentaion measurements showed a hardening phenomenon for the irradiated sample, and the hardness increment is higher in the case of high temperature irradiated sample. Dispersed barrier-hardening (DBH) model was applied to predict the hardening produced from the irradiation induced defects. The yield strength increment calculated based on TEM observations and the nanohardness increment measured using nanoindentation are in excellent agreement.

DMILL circuits. The hardened electronics decuples its performances

International Nuclear Information System (INIS)

Anon.

1998-01-01

Thanks to the DMILL (mixed logic-linear hardening) technology under development at the CEA, MHS, a French company specialized in the fabrication of integrated circuits now produces hardened electronic circuits ten times more resistant to radiations than its competitors. Outside the initial market (several thousands of circuits for the LHC particle accelerator of Geneva), a broad choice of applications is opened to this technology: national defense, space, civil nuclear and medical engineering, and high temperature applications. Short paper. (J.S.)

Preparation of Self Hardening-modelling Polyurethane for Wood Repairing and Cracks Injection

International Nuclear Information System (INIS)

Meligi, G.A.; Elnahas, H.H.; Ammar, A.H.

2014-01-01

Self hardening composite as a modelling clay was prepared from polyurethane, two parts (A) and (B) where (A) contains polyol (polyether), vinyl acetate versatic ester copolymer (VAcVe) and magnesium silicate or wood powder and (B) contains toluene diisocyanate (TDI) as a hardening agent. The two parts mixed thoroughly giving soft putty like feel, open working time 1-2 h and cures hard overnight (24 h full cure). Factors affecting working time and full cure were evaluated. Also, measurements of surface hardness, compressive strength, scanning electron microscopy (SEM), water absorption and effect of ionizing radiation were studied. The suggestion for using the prepared polyurethane composite as clay dries as hard as a rock in the field of wood repair and cracks injection for building walls were recommended. Keywords: Polyurethane, modelling clay, radiation, wood repair and cracks injection.

Age-hardening of an Al-Li-Cu-Mg alloy (2091) processed by high-pressure torsion

Energy Technology Data Exchange (ETDEWEB)

Lee, Seungwon, E-mail: chominamlsw@gmail.com [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); WPI, International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, Fukuoka 819-0395 (Japan); Horita, Zenji [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); WPI, International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, Fukuoka 819-0395 (Japan); Hirosawa, Shoichi [Department of Mechanical Engineering and Materials Science, Yokohama National University, Yokohama 240-8501 (Japan); Matsuda, Kenji [Graduate School of Science and Engineering for Research, University of Toyama, Toyama 930-8555 (Japan)

2012-06-01

This research presents the successful strengthening of an Al-Li-Cu-Mg alloy (2091) through the simultaneous use of grain refinement and age hardening. Following solid-solution treatment, the alloy was processed by high-pressure torsion (HPT) at room temperature and the grain size was refined to {approx}140 nm. The Vickers microhardness increased with increasing strain, and saturated to a constant level of 225 Hv. A further increase in the hardness to {approx}275 Hv was achieved by aging the HPT-processed alloy at 100 Degree-Sign C and 150 Degree-Sign C. Bending tests for the samples treated using the peak aging conditions demonstrated that the stress was significantly increased while considerable ductility was retained. Transmission electron microscopy revealed that the small grains are well retained even after prolonged aging, and the precipitation of fine {delta} Prime particles occurred within the small grains, which confirms that simultaneous strengthening from grain refinement and age hardening is feasible in this alloy.

Resonant frequency and elastic modulus measurements on hardened cement pastes

International Nuclear Information System (INIS)

Lee, D.J.

1982-12-01

A new technique for measuring resonant frequency and elastic modulus is described. This has been used on specimens of hardened cement paste containing water with no simulated waste, and the results compared with measurements of ultrasonic pulse velocity, dimensional movements and compressive strength made on the same formulations. In addition, measurements were made on a specimen containing simulated waste which demonstrated the applicability of the new technique for following the development of the mechanical properties of cemented simulant radioactive waste in the laboratory. (U.K.)

Effect of precipitate on yield strength of ferritic/martensitic steel exposed to 650 .deg. C liquid sodium

Energy Technology Data Exchange (ETDEWEB)

Kim, Tae Yong; Lee, Jeonghyeon; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of); Shin, Sang Hun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Ferritic/martensitic steels(FMS) which are used as one of cladding and structure materials in UCFR, have high creep strength at 600~650°C, low expansion coefficient, and dimensional stability with irradiation-induced void swelling in circumstance of fast neutrons compared to austenitic stainless steel. However, as exposed to high temperature liquid sodium during the design life time (30 to 60 years), the surface of FMS experienced Cr-depletion and decarburization by dissolution of components into sodium and formed oxidations by reacting with sodium. This changes chemical compositions of inter-surface and effects on behavior of precipitations. This change can cause a degradation of mechanical strength of structure material of UCFR. The research about FMS on effects of long term exposure in liquid sodium at 650 °C involve analysis of yield strength by change of microstructure, solid solution hardening and precipitation hardening. It shows how this three parts occupy total yield strength respectively and change over time. In a specific procedure, the microstructure and the surface phenomenon of FMS (Gr. 92) that are exposed to liquid sodium at 650°C, 20 ppm oxygen and are aged in high pure Argon gas environment to express bulk have been investigated by using scanning electron microscope (SEM) and transmission electron microscope (TEM). When specimens were exposed to 650 °C liquid sodium for 1583, 3095 hours and Ar-gas 1601, 2973 hours, mechanical properties of materials were analyzed quantitatively. After experiment, NaCrO{sub 2} oxidation was formed on the surface of Gr.92 at sodium environment. Also, change of microstructure, dissolution of elements, and nucleation and growth of precipitation was raised. During exposed to high temperature at sodium or Ar-gas, annealed lath structure as well as coarsening of tempered martensite structure affects reduction of mechanical properties. And dissolution of elements results in reduction of solid solution hardening. This

Influence of silica fume on the strength of high strength concrete

International Nuclear Information System (INIS)

Akram, T.; Memon, S.A.; Khan, S.A.

2007-01-01

HSC (High Strength Concrete) does not become evident by a sudden change in the behavior of 'ordinary strength' concrete. There is a gradual effect that becomes more noticeable when the strength level exceeds about 40-45 MPa. There cannot be a precise level of strength which defines this change in effect. The effects are on strength and workability, requiring us to take into account in our mix proportioning, the ramifications of fineness of cement on workability and of type of aggregate and aggregate/cement ratio on strength. In fact, the selection of materials becomes more critical as the concrete strength increases and that if very high strength is required (100 MPa and higher), relatively few materials may be suitable. An experimental investigation is carried out to evaluate the feasibility of producing HSC using locally available materials and to study the influence of silica fume on the strength of HSC. The main variables in this research is amount of silica fume. The parameters that are kept constant are the amount of cement equal to 580 kg/m3, dosage of HRWRA (High Range Water Reducing Admictures) equal to 4 % by weight of cementitious materials and the ratio of fine aggregate to coarse aggregate (1:2.3). Test results revealed that it is feasible to produce HSC using locally available materials. The optimum percentage of silica fume was found to be 15 % by weight of cement. (author)

Branching structure and strain hardening of branched metallocene polyethylenes

International Nuclear Information System (INIS)

Torres, Enrique; Li, Si-Wan; Costeux, Stéphane; Dealy, John M.

2015-01-01

There have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers

Branching structure and strain hardening of branched metallocene polyethylenes

Energy Technology Data Exchange (ETDEWEB)

Torres, Enrique; Li, Si-Wan; Costeux, Stéphane; Dealy, John M., E-mail: john.dealy@mcgill.ca [Department of Chemical Engineering, McGill University, Montreal, Quebec H3A 0C4 (Canada)

2015-09-15

There have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers.

Work hardening and plastic equation of state of tantalum

International Nuclear Information System (INIS)

Gypen, L.A.; Aernoudt, E.; Deruyttere, A.

1983-01-01

The influence of cold deformation on the thermal and athermal components of the flow stress of tantalum was investigated. Up to high deformation levels the strain hardening is due only to the development of internal stress fields; the effective stress remains almost constant. The athermal strain hardening of tantalum is parabolic at low deformation levels (epsilon < 0.5) and linear at high deformation levels, as for other bcc metals. Hart's plastic equation of state is shown to be valid for tantalum at room temperature in the whole deformation range investigated (from epsilon = 0.005 to epsilon = 2.8). (author)

Johnson-Cook Strength Model Constants for VascoMax 300 and 1080 Steels

International Nuclear Information System (INIS)

Cinnamon, J. D.; Palazotto, A. N.; Kennan, Z.; Brar, N. S.; Bajaj, D.

2006-01-01

High strength steels, VascoMax 300 and 1080, are characterized under tension at strain rates of ∼1/s, ∼500/s, ∼1000/s, and ∼1500/s and at high temperatures using the quasi-static and split Hopkinson bar techniques. The data on 1080 steel exhibited a typical strain hardening response, whereas Vasco-Max 300 steel showed diminishing flow stress beyond yielding because of localized necking in gauge section of the tested specimens. The tension data are analyzed to determine the Johnson-Cook (J-C) strength model constants for the two steels. The flow stress values for VascoMax are adjusted to account for necking, and the corrected J-C model is developed

Experiment research on grind-hardening of AISI5140 steel based on thermal copensation

Energy Technology Data Exchange (ETDEWEB)

Huang, Xiang Ming; Ren, Ying Hui; Zheng, Bo; Zhou, Zhixiong [College of Mechanical and Vehicle Engineering, Hunan University, Changsha, Hunan (China); Deng, Zhao Hui [Key Laboratory for High Efficiency and Precision Machining of Difficult-to-Cut Material of Hunan Province, Hunan (China)

2016-08-15

The grind-hardening process utilizes the heat generated to induce martensitic phase transformation. However, the maximum achievable harden layer depth is limited due to high grinding forces, and the tensile residual stress appears on the ground surface in the grind-hardening process. This paper proposes a new grind-hardening technology using thermal compensation. The workpiece of AISI5140 steel is preheated by electric resistance heating, and ground under the condition of the workpiece temperature 25°C, 120°C, 180°C and 240°C. The grinding force, harden layer depth and surface quality including residual stress on ground surface, surface roughness and micro-hardness are investigated. The experimental results show that a deep harden layer with a fine grain martensite can be obtained with the thermal compensation. The ground workpiece surface produces a certain compressive residual stress, and the residual compressive stress value increases with preheating temperature. As the preheating temperature increases, grinding force slightly decreases, while there is slightly increment of surface roughness. Compared with the conventional grind-hardening process, both the harden layer depth and residual stress distribution are significantly improved.

Hardening by ion implantation of VT1-0 alloy having different grain size

Energy Technology Data Exchange (ETDEWEB)

Nikonenko, Alisa, E-mail: aliska-nik@mail.ru; Kurzina, Irina, E-mail: kurzina99@mail.ru [National Research Tomsk State University, 36, Lenin Str., 634050, Tomsk (Russian Federation); Popova, Natalya, E-mail: natalya-popova-44@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk Russia (Russian Federation); Nikonenko, Elena, E-mail: vilatomsk@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30, Lenin Str., 634050, Tomsk (Russian Federation); Kalashnikov, Mark, E-mail: kmp1980@mail.ru [Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk Russia (Russian Federation)

2016-01-15

The paper presents a transmission electron microscopy (TEM) study of the structural and phase state of commercially pure titanium implanted by aluminum ions. TEM study has been carried out for two types of grains, namely coarse (0.4 µm) and small (0.5 µm). This paper presents details of the yield stress calculations and the analysis of strength components for the both grain types in two areas of the modified layer: at a distance of 0-150 nm (surface area I) and ∼300 nm (central area II) from the irradiated surface. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a different effect on the yield stress in areas I and II. Thus, near the ion-alloyed layer, the yield stress decreases with the increase of the grain size, whilst area II demonstrates its increase. Moreover, the contribution to the general hardening of the alloy made by certain hardening mechanisms differs from contributions made by each of these mechanisms in each certain case.

An improved Armstrong-Frederick-Type Plasticity Model for Stable Cyclic Stress-Strain Responses Considering Nonproportional Hardening

Science.gov (United States)

Li, Jing; Zhang, Zhong-ping; Li, Chun-wang

2018-03-01

This paper modified an Armstrong-Frederick-type plasticity model for investigating the stable cyclic deformation behavior of metallic materials with different sensitivity to nonproportional loadings. In the modified model, the nonproportionality factor and nonproportional cyclic hardening coefficient coupled with the Jiang-Sehitoglu incremental plasticity model were used to estimate the stable stress-strain responses of the two materials (1045HR steel and 304 stainless steel) under various tension-torsion strain paths. A new equation was proposed to calculate the nonproportionality factor on the basis of the minimum normal strain range. Procedures to determine the minimum normal strain range were presented for general multiaxial loadings. Then, the modified model requires only the cyclic strain hardening exponent and cyclic strength coefficient to determine the material constants. It is convenient for predicting the stable stress-strain responses of materials in engineering application. Comparisons showed that the modified model can reflect the effect of nonproportional cyclic hardening well.

Modeling copper precipitation hardening and embrittlement in a dilute Fe-0.3at.%Cu alloy under neutron irradiation

Science.gov (United States)

Bai, Xian-Ming; Ke, Huibin; Zhang, Yongfeng; Spencer, Benjamin W.

2017-11-01

Neutron irradiation in light water reactors can induce precipitation of nanometer sized Cu clusters in reactor pressure vessel steels. The Cu precipitates impede dislocation gliding, leading to an increase in yield strength (hardening) and an upward shift of ductile-to-brittle transition temperature (embrittlement). In this work, cluster dynamics modeling is used to model the entire Cu precipitation process (nucleation, growth, and coarsening) in a Fe-0.3at.%Cu alloy under neutron irradiation at 300°C based on the homogenous nucleation mechanism. The evolution of the Cu cluster number density and mean radius predicted by the modeling agrees well with experimental data reported in literature for the same alloy under the same irradiation conditions. The predicted precipitation kinetics is used as input for a dispersed barrier hardening model to correlate the microstructural evolution with the radiation hardening and embrittlement in this alloy. The predicted radiation hardening agrees well with the mechanical test results in the literature. Limitations of the model and areas for future improvement are also discussed in this work.

Experimental and numerical analysis of micromechanical damage in the punching process for High-Strength Low-Alloy steels

OpenAIRE

ACHOURI, Mohamed; GERMAIN, Guénaël; DAL SANTO, Philippe; SAIDANE, Delphine

2014-01-01

Sequential sheet metal forming processes can result in the accumulation of work hardening and damage effects in the workpiece material. The mechanical strength of the final component depends on the “evolution” of these two characteristics in the different production steps. The punching process, which is usually in the beginning of the production chain, has an important impact on the stress, strain and damage states in the punched zones. It is essential that the influence of these mechanical f...

Influence of Microstructure and Process Conditions on Simultaneous Low-Temperature Surface Hardening and Bulk Precipitation Hardening of Nanoflex®

DEFF Research Database (Denmark)

Bottoli, Federico; Winther, Grethe; Christiansen, Thomas L.

2015-01-01

Precipitation hardening martensitic stainless steel Nanoflex was low-temperature nitrided or nitrocarburized. In these treatments, simultaneous hardening of the bulk, by precipitation hardening, and the surface by dissolving nitrogen/carbon can be obtained because the treatment temperatures...... and times for these essentially different hardening mechanisms are compatible. The effect of the processing history of the steel on the nitrided/nitrocarburized case was investigated by varying the amounts of austenite and martensite through variation of the degree of plastic deformation by tensile strain...... consisting of martensite results in the deepest nitrided case, while a shallow case develops on a microstructure consisting of austenite. For an initial microstructure consisting of both martensite and austenite a non-uniform case depth is achieved. Simultaneous bulk and surface hardening is only possible...

Devising Strain Hardening Models Using Kocks–Mecking Plots—A Comparison of Model Development for Titanium Aluminides and Case Hardening Steel

Directory of Open Access Journals (Sweden)

Markus Bambach

2016-08-01

Full Text Available The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a sharp peak stress and pronounced softening. The work hardening behavior of a TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B alloy is studied using isothermal hot compression tests conducted on a Gleeble 3500 simulator, and compared to the typical case hardening steel 25MoCrS4. The behavior is analyzed with the help of the Kocks-Mecking plots. In contrast to steel the TNB-V4 alloy shows a non-linear course of θ (i.e., no stage-III hardening initially and exhibits neither a plateau (stage IV hardening nor an inflection point at all deformation conditions. The present paper describes the development and application of a methodology for the design of strain hardening models for the TNB-V4 alloy and the 25CrMoS4 steel by taking the course of the Kocks-Mecking plots into account. Both models use different approaches for the hardening and softening mechanisms and accurately predict the flow stress over a wide range of deformation conditions. The methodology may hence assist in further developments of more sophisticated physically-based strain hardening models for TiAl-alloys.

Generation of forming limit bands for ultra-high-strength steels in car body structures

Science.gov (United States)

Bayat, Hamid Reza; Sarkar, Sayantan; Italiano, Francesco; Bach, Aleksandar; Wulfinghoff, Stephan; Reese, Stefanie

2018-05-01

The application of ultra-high-strength steels in safety-related automotive components has led to higher safety levels as well as weight reduction. Nevertheless, this class of advanced high-strength steels (AHSS) show material scatter due to its manufacturing processes. To address this problem in advance, it is of significance not only to model the failure of the sheet metal but also to specify a band for the necking regime. The former is described by a forming limit curve (FLC), whereas a forming limit band (FLB) introduces the upper and lower bounds for the permissible strains. The objective of the present work is to generate a robust prediction of the strain-based failure of the sheet metal during a car crash. The FLCs are generated numerically applying a modified Marciniak-Kuczynski (MK) model, where the existence of an angled groove is mandatory. This assures to obtain the maximum admissible strain. In addition, a zero extension angle is utilized for the left hand side of the FLC (tension-compression). The material scatter is captured in experiments and applied in the hardening relations. Necking strains are recorded experimentally by a digital image correlation based system (ARAMIS). Later, they are fit into the FLC based on an inhomogeneity parameter fi from the MK model. In order to generate a theoretical FLB, first a statistical approach is exploited to take the experimental data into consideration. Eventually, the forming limit band distinguishes between safe, necking and failed regions.

Efficient simulation of press hardening process through integrated structural and CFD analyses

International Nuclear Information System (INIS)

Palaniswamy, Hariharasudhan; Mondalek, Pamela; Wronski, Maciek; Roy, Subir

2013-01-01

Press hardened steel parts are being increasingly used in automotive structures for their higher strength to meet safety standards while reducing vehicle weight to improve fuel consumption. However, manufacturing of sheet metal parts by press hardening process to achieve desired properties is extremely challenging as it involves complex interaction of plastic deformation, metallurgical change, thermal distribution, and fluid flow. Numerical simulation is critical for successful design of the process and to understand the interaction among the numerous process parameters to control the press hardening process in order to consistently achieve desired part properties. Until now there has been no integrated commercial software solution that can efficiently model the complete process from forming of the blank, heat transfer between the blank and tool, microstructure evolution in the blank, heat loss from tool to the fluid that flows through water channels in the tools. In this study, a numerical solution based on Altair HyperWorks® product suite involving RADIOSS®, a non-linear finite element based structural analysis solver and AcuSolve®, an incompressible fluid flow solver based on Galerkin Least Square Finite Element Method have been utilized to develop an efficient solution for complete press hardening process design and analysis. RADIOSS is used to handle the plastic deformation, heat transfer between the blank and tool, and microstructure evolution in the blank during cooling. While AcuSolve is used to efficiently model heat loss from tool to the fluid that flows through water channels in the tools. The approach is demonstrated through some case studies

Compressive and flexural strength of high strength phase change mortar

Science.gov (United States)

Qiao, Qingyao; Fang, Changle

2018-04-01

High-strength cement produces a lot of hydration heat when hydrated, it will usually lead to thermal cracks. Phase change materials (PCM) are very potential thermal storage materials. Utilize PCM can help reduce the hydration heat. Research shows that apply suitable amount of PCM has a significant effect on improving the compressive strength of cement mortar, and can also improve the flexural strength to some extent.

Effect of strengthening mechanisms on cold workability and instantaneous strain hardening behavior during grain refinement of AA 6061-10 wt.% TiO2 composite prepared by mechanical alloying

International Nuclear Information System (INIS)

Sivasankaran, S.; Sivaprasad, K.; Narayanasamy, R.; Iyer, Vijay Kumar

2010-01-01

Research highlights: → Various strengthening mechanisms such as solid solution, grain size, precipitate, dislocation and dispersion strengthening promoted yield strength of the composites → The 5 h sintered composite yielded a large plastic strain (23%) at ambient temperature. → The domination of interparticle friction effects, grain size and dislocation strengthening diminished the deformation capacity of the composites greater than 5 h of milling. → Ultra-fine grained composite (40 h) yielded a high strength (>1000 MPa). → The proposed instantaneous new Poisson's ratio and the instantaneous strain hardening index used to study the extent of plastic zone and strain levels of the composite. - Abstract: The mechanical alloying (MA) of AA 6061 alloy reinforced with 10 wt.% fine anatase-titania composites powder milled with different timings (1, 5, 10, 20, 30, and 40 h) was cold consolidated and sintered. The main purpose of this study is to investigate the effect of microstructure and the various strengthening mechanisms such as solid solution, grain size, precipitate, dislocation and dispersion strengthening during grain refinement of AA 6061-10 wt.% TiO 2 composite via MA on cold working and strain hardening behavior. The sintered composite preforms were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope. The strengthening mechanisms were estimated by using simplified models available in the literatures. The evaluation of cold deformation behavior under triaxial stress condition through room temperature cold-upsetting tests (incremental loads) was studied by correlating the strengthening mechanisms. Among the developed strengthening mechanisms the grain size and dislocation strengthening mechanisms diminished the deformation capacity of the composites. The strain hardening behavior was also examined by proposing instantaneous strain hardening index (n i ). The value of maximum instantaneous strain

Influences of Steelmaking Slags on Hydration and Hardening of Concretes

Science.gov (United States)

Kirsanova, A. A.; Dildin, A. N.; Maksimov, S. P.

2017-11-01

It is shown that the slag of metallurgical production can be used in the construction industry as an active mineral additive for concrete. This approach allows us to solve environmental problems and reduce costs for the production of binder and concrete simultaneously. Most often slag is used in the form of a filler, an active mineral additive or as a part of a binder for artificial conglomerates. The introduction of slag allows one to notice a part of the cement, to obtain concretes that are more resistant to the impact of aggressive sulfate media. The paper shows the possibility of using recycled steel-smelting slags in the construction industry for the production of cement. An assessment was made of their effect on the hydration of the cement stone and hardening of the concrete together with the plasticizer under normal conditions. In the process of work, we used the slag of the Zlatoust Electrometallurgical Factory. Possible limitations of the content of steel-slag slag in concrete because of the possible presence of harmful impurities are shown. It is necessary to enter slag in conjunction with superplasticizers to reduce the flow of water mixing. Slags can be used as a hardening accelerator for cement concrete as they allow one to increase the degree of cement hydration and concrete strength. It is shown that slags can be used to produce fast-hardening concretes and their comparative characteristics with other active mineral additives are given.

Thermophysical and Mechanical Properties of Hardened Cement Paste with Microencapsulated Phase Change Materials for Energy Storage

Directory of Open Access Journals (Sweden)

Hongzhi Cui

2014-12-01

Full Text Available In this research, structural-functional integrated cement-based materials were prepared by employing cement paste and a microencapsulated phase change material (MPCM manufactured using urea-formaldehyde resin as the shell and paraffin as the core material. The encapsulation ratio of the MPCM could reach up to 91.21 wt%. Thermal energy storage cement pastes (TESCPs incorporated with different MPCM contents (5%, 10%, 15%, 20% and 25% by weight of cement were developed, and their thermal and mechanical properties were studied. The results showed that the total energy storage capacity of the hardened cement specimens with MPCM increased by up to 3.9-times compared with that of the control cement paste. The thermal conductivity at different temperature levels (35–36 °C, 55–56 °C and 72–74 °C decreased with the increase of MPCM content, and the decrease was the highest when the temperature level was 55–56 °C. Moreover, the compressive strength, flexural strength and density of hardened cement paste decreased with the increase in MPCM content linearly. Among the evaluated properties, the compressive strength of TESCPs had a larger and faster degradation with the increase of MPCM content.

High-temperature strength of AISI 316 steel

International Nuclear Information System (INIS)

Antunes, A.E.B.; Monteiro, S.N.

1975-01-01

The mechanical properties, especially elastic limit and strain hardening of AISI-316 austenitic stainless steel were investigated within the temperature range 150-800 0 C for two strain rates. The results showed anomalous behaviour between 200 and 650 0 C, over which range there was an increase in maximum strenght and hardening, with a tendency to show peaks. These apparentley three in number, may be connected with the effects of interaction between point defects and dislocations leading to dinamic aging phenomena. The mechanisms responsible for this anomalous behaviour produce a negative dependence on strain rate [pt

Structure and properties of steel case-hardened by non-vacuum electron-beam cladding of carbon fibers

Science.gov (United States)

Losinskaya, A. A.; Lozhkina, E. A.; Bardin, A. I.

2017-12-01

At the present time, the actual problem of materials science is the increase in the steels performance characteristics. In the paper some mechanical properties of the case-hardened materials received by non-vacuum electron-beam cladding of carbon fibers are determined. The depth of the hardened layers varies from 1.5 to 3 mm. The impact strength of the samples exceeds 50 J/cm2. The wear resistance of the coatings obtained exceeds the properties of steel 20 after cementation and quenching with low tempering. The results of a study of the microhardness of the resulting layers and the microstructure are also given. The hardness of the surface layers exceeds 5700 MPa.

Challenges in hardening technologies using shallow-trench isolation

International Nuclear Information System (INIS)

Shaneyfelt, M.R.; Dodd, P.E.; Draper, B.L.; Flores, R.S.

1998-02-01

Challenges related to radiation hardening CMOS technologies with shallow-trench isolation are explored. Results show that trench hardening can be more difficult than simply replacing the trench isolation oxide with a hardened field oxide

Hirarchical structures and strength in cold-drawn pearlitic steel wire

DEFF Research Database (Denmark)

Zhang, Xiaodan; Hansen, Niels; Godfrey, Andrew

2014-01-01

and the cementite decomposition, have been analyzed and quantified by scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy for wires cold drawn up to a strain of 3.68. Three strengthening mechanisms, boundary strengthening, dislocation strengthening and solid...... solution hardening, have been analyzed based on the microstructural analysis. The individual and combined contributions, of these mechanisms to the wire strength have been estimated and good agreement has been found between the measured flow stress and values estimated based on an assumption of linear...... additivity of the three strengthening mechanisms. Mechanisms behind the higher strength of about 6.4 GPa in the wires drawn to higher strains and to a finer microstructural scale is also discussed....

Nitrogen nutrition and drought hardening exert opposite effects on the stress tolerance of Pinus pinea L. seedlings.

Science.gov (United States)

Villar-Salvador, Pedro; Peñuelas, Juan L; Jacobs, Douglass F

2013-02-01

Functional attributes determine the survival and growth of planted seedlings in reforestation projects. Nitrogen (N) and water are important resources in the cultivation of forest species, which have a strong effect on plant functional traits. We analyzed the influence of N nutrition on drought acclimation of Pinus pinea L. seedlings. Specifically, we addressed if high N fertilization reduces drought and frost tolerance of seedlings and whether drought hardening reverses the effect of high N fertilization on stress tolerance. Seedlings were grown under two N fertilization regimes (6 and 100 mg N per plant) and subjected to three drought-hardening levels (well-watered, moderate and strong hardening). Water relations, gas exchange, frost damage, N concentration and growth at the end of the drought-hardening period, and survival and growth of seedlings under controlled xeric and mesic outplanting conditions were measured. Relative to low-N plants, high-N plants were larger, had higher stomatal conductance (27%), residual transpiration (11%) and new root growth capacity and closed stomata at higher water potential. However, high N fertilization also increased frost damage (24%) and decreased plasmalemma stability to dehydration (9%). Drought hardening reversed to a great extent the reduction in stress tolerance caused by high N fertilization as it decreased frost damage, stomatal conductance and residual transpiration by 21, 31 and 24%, respectively, and increased plasmalemma stability to dehydration (8%). Drought hardening increased tissue non-structural carbohydrates and N concentration, especially in high-fertilized plants. Frost damage was positively related to the stability of plasmalemma to dehydration (r = 0.92) and both traits were negatively related to the concentration of reducing soluble sugars. No differences existed between moderate and strong drought-hardening treatments. Neither N nutrition nor drought hardening had any clear effect on seedling

Texture, deformation twinning and hardening in a newly developed Mg-Dy-Al-Zn-Zr alloy processed with high pressure torsion

Czech Academy of Sciences Publication Activity Database

Kocich, R.; Kunčická, L.; Král, Petr; Lowe, T. C.

2016-01-01

Roč. 90, JAN (2016), s. 1092-1099 ISSN 0264-1275 Institutional support: RVO:68081723 Keywords : Magnesium * High pressure torsion * Texture * Deformation twinning * Hardening Subject RIV: JG - Metallurgy Impact factor: 4.364, year: 2016

Stress corrosion cracking evaluation of martensitic precipitation hardening stainless steels

Science.gov (United States)

Humphries, T. S.; Nelson, E. E.

1980-01-01

The resistance of the martensitic precipitation hardening stainless steels PH13-8Mo, 15-5PH, and 17-4PH to stress corrosion cracking was investigated. Round tensile and c-ring type specimens taken from several heats of the three alloys were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, to salt spray, and to a seacoast environment. The results indicate that 15-5PH is highly resistant to stress corrosion cracking in conditions H1000 and H1050 and is moderately resistant in condition H900. The stress corrosion cracking resistance of PH13-8Mo and 17-4PH stainless steels in conditions H1000 and H1050 was sensitive to mill heats and ranged from low to high among the several heats included in the tests. Based on a comparison with data from seacoast environmental tests, it is apparent that alternate immersion in 3.5 percent salt water is not a suitable medium for accelerated stress corrosion testing of these pH stainless steels.

On the Spectral Hardening at gsim300 keV in Solar Flares

Science.gov (United States)

Li, G.; Kong, X.; Zank, G.; Chen, Y.

2013-05-01

It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies gsim300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ~k -2.7. A ~k -2.7 dissipation range spectrum is consistent with recent solar wind observations.

Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

Energy Technology Data Exchange (ETDEWEB)

Fukuda, Makoto, E-mail: makoto.fukuda@qse.tohoku.ac.jp [Tohoku University, Sendai, 980-8579 (Japan); Kiran Kumar, N.A.P.; Koyanagi, Takaaki; Garrison, Lauren M. [Oak Ridge National Laboratory, Oak Ridge, TN, 37831 (United States); Snead, Lance L. [Massachusetts Institute of Technology, Cambridge, MA, 02139 (United States); Katoh, Yutai [Oak Ridge National Laboratory, Oak Ridge, TN, 37831 (United States); Hasegawa, Akira [Tohoku University, Sendai, 980-8579 (Japan)

2016-10-15

Neutron irradiation to single crystal pure tungsten was performed in the mixed spectrum High Flux Isotope Reactor (HFIR). To investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ∼90–∼800 °C and fast neutron fluences were 0.02–9.00 × 10{sup 25} n/m{sup 2} (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. The hardness and microstructure changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 10{sup 25} n/m{sup 2} (E > 0.1 MeV). Irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 10{sup 25} n/m{sup 2} (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten. - Highlights: • The microstructure and irradiation hardening of single crystal pure W irradiated in HFIR was investigated. • The neutron energy spectrum influence was evaluated by comparing the HFIR results with previous work in Joyo and JMTR. • In the dose range up to ∼1 dpa, the neutron energy spectrum influence of irradiation hardening was not clear. • In the dose range above 1 dpa, the neutron energy influence on irradiation hardening and microstructural development was clearly observed. • The irradiation induced precipitates caused significant irradiation hardening of pure W irradiated in HFIR.

Significance of rate of work hardening in tempered martensite embrittlement

International Nuclear Information System (INIS)

Pietikainen, J.

1995-01-01

The main explanations for tempered martensite embrittlement are based on the effects of impurities and cementite precipitation on the prior austenite grain boundaries. There are some studies where the rate of work hardening is proposed as a potential reason for the brittleness. One steel was studied by means of a specially developed precision torsional testing device. The test steel had a high Si and Ni content so ε carbide and Fe 3 C appear in quite different tempering temperature ranges. The M S temperature is low enough so that self tempering does not occur. With the testing device it was possible to obtain the true stress - true strain curves to very high deformations. The minimum toughness was always associated with the minimum of rate of work hardening. The change of deformed steel volume before the loss of mechanical stability is proposed as at least one reason for tempered martensite embrittlement. The reasons for the minimum of the rate of work hardening are considered. (orig.)

Laser Surface Hardening of Groove Edges

Science.gov (United States)

Hussain, A.; Hamdani, A. H.; Akhter, R.; Aslam, M.

2013-06-01

Surface hardening of groove-edges made of 3Cr13 Stainless Steel has been carried out using 500 W CO2 laser with a rectangular beam of 2.5×3 mm2. The processing speed was varied from 150-500 mm/min. It was seen that the hardened depth increases with increase in laser interaction time. A maximum hardened depth of around 1mm was achieved. The microhardness of the transformed zone was 2.5 times the hardness of base metal. The XRD's and microstructural analysis were also reported.

Development of LTCC Materials with High Mechanical Strength

International Nuclear Information System (INIS)

Kawai, Shinya; Nishiura, Sousuke; Terashi, Yoshitake; Furuse, Tatsuji

2011-01-01

We have developed LTCC materials suitable for substrates of RF modules used in mobile phone. LTCC can provide excellent solutions to requirements of RF modules, such as down-sizing, embedded elements and high performance. It is also important that LTCC material has high mechanical strength to reduce risk of fracture by mechanical impact. We have established a method of material design for high mechanical strength. There are two successive steps in the concept to achieve high mechanical strength. The first step is to improve mechanical strength by increasing the Young's modulus, and the second step is either further improvement through the Young's modulus or enhancement of the fracture energy. The developed material, so called high-strength LTCC, thus possesses mechanical strength of 400MPa, which is twice as strong as conventional material whose mechanical strength is approximately 200MPa in typical. As a result, high-strength LTCC shows an excellent mechanical reliability, against the drop impact test for example. The paper presents material design and properties of LTCC materials.

Study on creep of fiber reinforced ultra-high strength concrete based on strength

Science.gov (United States)

Peng, Wenjun; Wang, Tao

2018-04-01

To complement the creep performance of ultra-high strength concrete, the long creep process of fiber reinforced concrete was studied in this paper. The long-term creep process and regularity of ultra-high strength concrete with 0.5% PVA fiber under the same axial compression were analyzed by using concrete strength (C80/C100/C120) as a variable. The results show that the creep coefficient of ultra-high strength concrete decreases with the increase of concrete strength. Compared with ACI209R (92), GL2000 models, it is found that the predicted value of ACI209R (92) are close to the experimental value, and the creep prediction model suitable for this experiment is proposed based on ACI209R (92).

Strength and water absorption characteristics of cement-bonded ...

African Journals Online (AJOL)

Contrary to conventional practice, the boards were fabricated in the laboratory without external pressure application. The effects of calcium chloride (CaCl2) addition on the hardening time, appearance, bending and compressive strength, and water absorption properties of the boards were also investigated. The boards had ...

A Fine Grain, High Mn Steel with Excellent Cryogenic Temperature Properties and Corresponding Constitutive Behaviour

Directory of Open Access Journals (Sweden)

Yuhui Wang

2018-02-01

Full Text Available A Fe-34.5 wt % Mn-0.04 wt % C ultra-high Mn steel with a fully recrystallised fine-grained structure was produced by cold rolling and subsequent annealing. The steel exhibited excellent cryogenic temperature properties with enhanced work hardening rate, high tensile strength, and high uniform elongation. In order to capture the unique mechanical behaviour, a constitutive model within finite strain plasticity framework based on Hill-type yield function was established with standard Armstrong-Frederick type isotropic hardening. In particular, the evolution of isotropic hardening was determined by the content of martensite; thus, a relationship between model parameters and martensite content is built explicitly.

Quenching and hardening in the transverse quasi-elastic peak

International Nuclear Information System (INIS)

Alberico, W.M.; Molinari, A.; Ericson, M.

1981-09-01

We study in the RPA framework the response of symmetric, infinite nuclear matter to a spin-isospin sensitive probe with both σ.q and σ.xq couplings. The two responses, similar in the low-q region, differ markedly for moderate momenta (>=1fm -1 ). Indeed, whereas the longitudinal one displays a softening and an enhancement (due to the attractive character of the associated particle-hole force), the transverse response is quenched and hardened with respect to the free Fermi gas. The existing experimental data, which we analyze, are compatible with our results. We also explore the total strengths and find that for repulsive forces they are appreciably reduced by the RPA correlations. Large part of this quenching comes from the Δ excitation (LLEE effect), but some reduction is still present even when the nucleonic degrees of freedom are neglected. This illustrates a violation of strength conservation brougth about by the RPA correlations in the spin-isospin channel

Strong work-hardening behavior induced by the solid solution strengthening of dendrites in TiZr-based bulk metallic glass matrix composites

Energy Technology Data Exchange (ETDEWEB)

Ma, D.Q. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Jiao, W.T. [College of Education, Hebei Normal University of Science and Technology, Qinhuangdao 066004 (China); Zhang, Y.F. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Hebei Vocational and Technical College of Building Materials, Qinhuangdao 066004 (China); Wang, B.A.; Li, J.; Zhang, X.Y. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Ma, M.Z., E-mail: mz550509@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Liu, R.P. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

2015-03-05

Highlights: • Hardness of dendrite of TiZr-based BMGMCs increases. • Strong work-hardening behavior is obtained after solid solution strengthening. • Lattice distortions of dendrite suffering from rapid cooling are detected. - Abstract: A series of TiZr-based bulk metallic glass matrix composites (BMGMCs) with distinguished mechanical properties are successfully fabricated by adding different volume fractions of Ta (Ti{sub 38.8}Zr{sub 28.8}Cu{sub 6.2}Be{sub 16.2}Nb{sub 10} as the basic composition, denoted as Ta{sub 0.0}–Ta{sub 8.0}). Along with the growth of precipitated phase, typical dendritic morphology is fully developed in the TiZr-based BMGMCs of Ta{sub 8.0}. Energy-dispersive spectrometry analysis of the dendrites and glass matrix indicates that the metallic elements of Nb and Ta should preferentially form solid solution into dendrites. The chaotic structure of high-temperature precipitate phase is trapped down by the rapid cooling of the copper-mould. The detected lattice distortions in the dendrites are attributed to the strong solid solution strengthening of the metallic elements of Ti, Zr, Nb, and Ta. These lattice distortions increase the resistance of the dislocation motion and pin the dislocations, thus the strength and hardness of dendrite increase. Dendrites create a strong barrier for the shear band propagation and generate multiple shear bands after solid solution strengthening, thereby providing the TiZr-based BMGMCs with greatly improved capacity to sustain plastic deformation and resistance to brittle fracture. Thus, the TiZr-based BMGMCs possess distinguished work-hardening capability. Among these TiZr-based BMGMCs, the sample Ta{sub 0.5} possesses the largest plastic strain (ε{sub p}) at 20.3% and ultimate strength (σ{sub max}) of 2613 MPa during compressive loading. In addition, the sample of Ta{sub 0.5} exhibits work-hardening up to an ultrahigh tensile strength of 1680 MPa during the tensile process, and then progressively

Nano Precipitation and Hardening of Die-Quenched 6061 Aluminum Alloy.

Science.gov (United States)

Utsunomiya, Hiroshi; Tada, Koki; Matsumoto, Ryo; Watanabe, Katsumi; Matsuda, Kenji

2018-03-01

Die quenching is applied to an age-hardenable aluminium alloys to obtain super-saturated solid solution. The application is advantageous because it can reduce number of manufacturing processes, and may increase strength by strain aging. If die quenching is realized in forging as well as sheet forming, it may widen industrial applicability further. In this study, Al-Mg-Si alloy AA6061 8 mm-thick billets were reduced 50% in height without cracks by die-quench forging. Supersaturated solid solution was successfully obtained. The die-quenched specimen shows higher hardness with nano precipitates at shorter aging time than the conventional water-quenched specimen.

Review on fatigue behavior of high-strength concrete after high temperature

Science.gov (United States)

Zhao, Dongfu; Jia, Penghe; Gao, Haijing

2017-06-01

The fatigue of high-strength concrete after high temperature has begun to attract attention. But so far the researches work about the fatigue of high-strength concrete after high temperature have not been reported. This article based on a large number of literature. The research work about the fatigue of high-strength concrete after high temperature are reviewed, analysed and expected, which can provide some reference for the experimental study of fatigue damage analysis.

Hardening Embrittlement and Non-Hardening Embrittlement of Welding-Heat-Affected Zones in a Cr-Mo Low Alloy Steel

Directory of Open Access Journals (Sweden)

Yu Zhao

2018-06-01

Full Text Available The embrittlement of heat affected zones (HAZs resulting from the welding of a P-doped 2.25Cr-1Mo steel was studied by the analysis of the fracture appearance transition temperatures (FATTs of the HAZs simulated under a heat input of 45 kJ/cm with different peak temperatures. The FATTs of the HAZs both with and without tempering increased with the rise of the peak temperature. However, the FATTs were apparently lower for the tempered HAZs. For the as-welded (untempered HAZs, the FATTs were mainly affected by residual stress, martensite/austenite (M/A islands, and bainite morphology. The observed embrittlement is a hardening embrittlement. On the other hand, the FATTs of the tempered HAZs were mainly affected by phosphorus grain boundary segregation, thereby causing a non-hardening embrittlement. The results demonstrate that the hardening embrittlement of the as-welded HAZs was more severe than the non-hardening embrittlement of the tempered HAZs. Consequently, a post-weld heat treatment should be carried out if possible so as to eliminate the hardening embrittlement.

Precipitation hardening in a 12%Cr-9%Ni-4%Mo-2%Cu stainless steel

International Nuclear Information System (INIS)

Haettestrand, Mats; Nilsson, Jan-Olof; Stiller, Krystyna; Liu Ping; Andersson, Marcus

2004-01-01

A combination of complementary techniques including one-dimensional and three-dimensional atom probe, energy-filtered transmission electron microscopy and conventional transmission electron microscopy has been used to assess the precipitation reactions at 475 deg. C in a 12%Cr-9%Ni-4%Mo-2%Cu precipitation hardening stainless steel. The continuous hardening up to at least 1000 h of ageing was attributed to a sequence of precipitation reactions involving nickel-rich precipitates nucleating at copper clusters followed by molybdenum-rich quasicrystalline precipitates and nickel-rich precipitates of type L1 0 . An estimate of the relative contributions to the strength increment during tempering based on measurements of particle densities was performed. Nickel-rich precipitates were found to play the most important role up to about 40 h of ageing after which the effect of quasicrystalline particles became increasingly important

Radiation-chemical hardening of phenol-formaldehyde oligomers

International Nuclear Information System (INIS)

Shlapatskaya, V.V.; Omel'chenko, S.I.

1978-01-01

Radiation-chemical hardening of phenol formaldehyde oligomers of the resol type has been studied in the presence of furfural and diallylphthalate diluents. The samples have been hardened on an electron accelerator at an electron energy of 1.0-1.1 MeV and a dose rate of 2-3 Mrad/s. The kinetics of hardening has been studied on the yield of gel fraction within the range of absorbed doses from 7 to 400 Mrad. Radiation-chemical hardening of the studied compositions is activated with sensitizers, namely, amines, metal chlorides, and heterocyclic derivatives of metals. Furfural and diallylphthalate compositions are suitable for forming glass-fibre plastic items by the wet method and coatings under the action of ionizing radiations

Environmental hardening of a mobile-manipulator system for nuclear environments

International Nuclear Information System (INIS)

Jones, S.L.; Cable, T.; Tulenko, J.S.; Toshkov, S.; Sias, F.R. Jr.

1993-01-01

This research report discusses the radiation hardening of a commercially available mobile robot, the REMOTEC ANDROS. This hardening effort is culminating in the availability of a megarad hardened mobile platform to access areas in nuclear facilities with extremely high levels of radiation (0.1 to 1 Mrad). These radiation levels may be encountered both during routine repair and monitoring activities and accident situations. The project has completed a phase-I U.S. Department of Energy Small Business Innovative Research contract and is now in a phase-II effort with completion scheduled in early 1995. The research involves the evaluation of the material and electrical components of an ANDROS robot to determine the anticipated radiation hardness of the current production version and evaluation of the components that must be replaced or modified to harden the system to higher radiation levels. The work being reported is based on an evaluation of the complete list of all electronic, electrical, and mechanical parts used in the robot and includes initial experimental radiation evaluations performed at the University of Florida

Application of a three-feature dispersed-barrier hardening model to neutron-irradiated Fe-Cr model alloys

Science.gov (United States)

Bergner, F.; Pareige, C.; Hernández-Mayoral, M.; Malerba, L.; Heintze, C.

2014-05-01

An attempt is made to quantify the contributions of different types of defect-solute clusters to the total irradiation-induced yield stress increase in neutron-irradiated (300 °C, 0.6 dpa), industrial-purity Fe-Cr model alloys (target Cr contents of 2.5, 5, 9 and 12 at.% Cr). Former work based on the application of transmission electron microscopy, atom probe tomography, and small-angle neutron scattering revealed the formation of dislocation loops, NiSiPCr-enriched clusters and α‧-phase particles, which act as obstacles to dislocation glide. The values of the dimensionless obstacle strength are estimated in the framework of a three-feature dispersed-barrier hardening model. Special attention is paid to the effect of measuring errors, experimental details and model details on the estimates. The three families of obstacles and the hardening model are well capable of reproducing the observed yield stress increase as a function of Cr content, suggesting that the nanostructural features identified experimentally are the main, if not the only, causes of irradiation hardening in these model alloys.

Properties of fresh and hardened sustainable concrete due to the use of palm oil fuel ash as cement replacement

Science.gov (United States)

Hamada, Hussein M.; Jokhio, Gul Ahmed; Mat Yahaya, Fadzil; Humada, Ali M.

2018-04-01

Palm oil fuel ash (POFA) is a by-product resulting from the combustion of palm oil waste such as palm oil shell and empty fruit bunches to generate electricity in the palm oil mills. Considerable quantities of POFA thus generated, accumulate in the open fields and landfills, which causes atmospheric pollution in the form of generating toxic gases. Firstly, to protect the environment; and secondly, having excellent properties for this purpose; POFA can be and has been used as partial cement replacement in concrete preparation. Therefore, this paper compiles the results obtained from previous studies that address the properties of concrete containing POFA as cement replacement in fresh and hardened states. The results indicate that there is a great potential to using POFA as cement replacement because of its ability to improve compressive strength, reduce hydration heat of cement mortar and positively affect other fresh and hardened concrete properties. The paper recommends that conducting further studies to exploit high volume of POFA along with other additives as cement replacement while maintaining high quality of concrete can help minimize CO2 emissions due to concrete.

Strain Rate Effect on Tensile Behavior for a High Specific Strength Steel: From Quasi-Static to Intermediate Strain Rates

Directory of Open Access Journals (Sweden)

Wei Wang

2017-12-01

Full Text Available The strain rate effect on the tensile behaviors of a high specific strength steel (HSSS with dual-phase microstructure has been investigated. The yield strength, the ultimate strength and the tensile toughness were all observed to increase with increasing strain rates at the range of 0.0006 to 56/s, rendering this HSSS as an excellent candidate for an energy absorber in the automobile industry, since vehicle crushing often happens at intermediate strain rates. Back stress hardening has been found to play an important role for this HSSS due to load transfer and strain partitioning between two phases, and a higher strain rate could cause even higher strain partitioning in the softer austenite grains, delaying the deformation instability. Deformation twins are observed in the austenite grains at all strain rates to facilitate the uniform tensile deformation. The B2 phase (FeAl intermetallic compound is less deformable at higher strain rates, resulting in easier brittle fracture in B2 particles, smaller dimple size and a higher density of phase interfaces in final fracture surfaces. Thus, more energy need be consumed during the final fracture for the experiments conducted at higher strain rates, resulting in better tensile toughness.

Radiation hardening and embrittlement of some refractory metals and alloys

International Nuclear Information System (INIS)

Fabritsiev, S.; Pokrovskyb

2007-01-01

Tungsten is proposed for application in the ITER divertor and limiter as plasma facing material. The tungsten operation temperature in the ITER divertor is relatively high. Hence, the ductile properties of tungsten will be controlled by the low temperature radiation embrittlement. The mechanism of radiation hardening and embrittlement under neutron irradiation at low temperature is well studied for FCC metals, in particular for copper. At the same time, low-temperature radiation hardening of BCC materials, in particular for refractory metals, is less studied. This study presents the results of investigation into radiation hardening and embrittlement of pure metals: W, Mo and Nb, and W-Re and Ta-4W alloys. The materials were in the annealed conditions. The specimens were irradiated in the SM-2 reactor to doses of 10 -4 -10 -1 dpa at 80 C and then tested for tension at 80 C. The study of the stress-strain curves of unirradiated specimens revealed a yield drop for W, Mo, Nb, Ta-4W, W-Re. After the yield drop some metals (Mo,Nb) retain their capability for strain hardening and demonstrate a high elongation (20-50%). Radiation hardening is maximum in Mo (∝400MPa) and minimum in Nb (∝100 MPa). In this case the dependence slope for Nb is similar to that for pure copper irradiated in SM-2 under the same conditions. Ii and Ta-4W have a higher slope. Measurement of electrical resistivity of irradiated specimens showed that for all materials it is increased monotonously with an increase in the irradiation dose. A minimum gain in electrical resistivity with a dose was observed for Nb (∝3% at 0.1 dpa). As for Mo it was essentially higher, i.e. ∝ 30%. The gain was maximum for W-Re alloy. Comparison of radiation hardening dose dependencies obtained in this study with the data for FCC metals (Cu) showed that in spite of the quantitative difference the qualitative behavior of these two classes of metals is similar. (orig.)

Microstructural evolution, mechanical properties, and strain hardening behavior of ultrafine grained commercial pure copper during the accumulative roll bonding process

Energy Technology Data Exchange (ETDEWEB)

Fattah-alhosseini, A. [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Imantalab, O., E-mail: o.imantalab@gmail.com [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Mazaheri, Y. [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Keshavarz, M.K. [Department of Engineering Physics, Polytechnique Montreal, Montreal (Canada)

2016-01-05

In this study, the microstructural evolution, mechanical properties, and strain hardening behavior of commercial pure copper processed by the accumulative roll bonding (ARB) were investigated. Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) images indicated that with increasing the number of ARB cycles, the grain size of samples decreased. An Ultrafine grained (UFG) structure with an average grain size of about 200 nm was achieved after four cycles of ARB. The yield and ultimate tensile strength of pure copper with the UFG microstructure was reached about 360 MPa and 396 MPa (about 400% and 100% higher than that of the annealed state), respectively. All ARB-processed copper samples showed lower strain hardening exponent in comparison with the annealed state. Moreover, the strain hardening rate increased with increasing ARB cycles up to 3 cycles and then decreased.

Microstructural evolution, mechanical properties, and strain hardening behavior of ultrafine grained commercial pure copper during the accumulative roll bonding process

International Nuclear Information System (INIS)

Fattah-alhosseini, A.; Imantalab, O.; Mazaheri, Y.; Keshavarz, M.K.

2016-01-01

In this study, the microstructural evolution, mechanical properties, and strain hardening behavior of commercial pure copper processed by the accumulative roll bonding (ARB) were investigated. Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) images indicated that with increasing the number of ARB cycles, the grain size of samples decreased. An Ultrafine grained (UFG) structure with an average grain size of about 200 nm was achieved after four cycles of ARB. The yield and ultimate tensile strength of pure copper with the UFG microstructure was reached about 360 MPa and 396 MPa (about 400% and 100% higher than that of the annealed state), respectively. All ARB-processed copper samples showed lower strain hardening exponent in comparison with the annealed state. Moreover, the strain hardening rate increased with increasing ARB cycles up to 3 cycles and then decreased.

ON THE SPECTRAL HARDENING AT ∼>300 keV IN SOLAR FLARES

International Nuclear Information System (INIS)

Li, G.; Kong, X.; Zank, G.; Chen, Y.

2013-01-01

It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies ∼>300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ∼k –2.7 . A ∼k –2.7 dissipation range spectrum is consistent with recent solar wind observations.

Induction hardening of tool steel for heavily loaded aircraft engine components

Directory of Open Access Journals (Sweden)

Rokicki P.

2017-03-01

Full Text Available Induction hardening is an innovative process allowing modification of the materials surface with more effective, cheaper and more reproducible way to compare with conventional hardening methods used in the aerospace industry. Unfortunately, high requirements and strict regulation concerning this branch of the industry force deep research allowing to obtain results that would be used for numerical modelling of the process. Only by this way one is able to start the industrial application of the process. The main scope of presented paper are results concerning investigation of microstructure evolution of tool steel after single-frequency induction hardening process. The specimens that aim in representing final industrial products (as heavily loaded gears, were heat- -treated with induction method and subjected to metallographic preparation, after which complex microstructure investigation was performed. The results obtained within the research will be a basis for numerical modelling of the process of induction hardening with potential to be introduced for the aviation industrial components.

Possible Applications of Hardening Slurries with Fly Ash from Thermal Treatment of Municipal Sewage Sludge in Environmental Protection Structures

Science.gov (United States)

Falacinski, Paweł; Szarek, Łukasz

2016-06-01

In Poland, in recent years, there has been a rapid accumulation of sewage sludge - a by-product in the treatment of urban wastewater. This has come about as a result of infrastructure renewal, specifically, the construction of modern sewage treatment plants. The more stringent regulations and strategic goals adopted for modern sewage management have necessitated the application of modern engineering methodology for the disposal of sewage sludge. One approach is incineration. As a consequence, the amount of fly ash resulting from the thermal treatment of municipal sewage sludge has grown significantly. Hence, intensive work is in progress for environmentally safe management of this type of waste. The aim of the experiment was to evaluate the possibility of using the fly ash that results from municipal sewage sludge thermal treatment (SSTT) as an additive to hardening slurries. This type of hardening slurry with various types of additives, e.g. coal combustion products, is used in the construction of cut-off walls in hydraulic structures. The article presents the technological and functional parameters of hardening slurries with an addition of fly ash obtained by SSTT. Moreover, the usefulness of these slurries is analysed on the basis of their basic properties, i.e. density, contractual viscosity, water separation, structural strength, volumetric density, hydraulic conductivity, compressive and tensile strength. The mandated requirements for slurries employed in the construction of cut-off walls in flood embankments are listed as a usefulness criteria. The article presents the potential uses of fly ash from SSTT in hardening slurry technology. It also suggests directions for further research to fully identify other potential uses of this by-product in this field.

Analysis of the strain-aging phenomena in high purity niobium: competition between hardening and recovery

International Nuclear Information System (INIS)

Andreone, C.; Cizeron, G.; Larere, A.

1981-01-01

The strain-aging phenomena in high purity niobium were studied using tensile tests. Four parameters were considered which characterize the yield point, the permanent hardening, the recovery and the apparent yield stress. Five successive steps can be distinguished from the changes in these parameters with changes in the aging temperature. The detailed analysis of the phenomena involved concerns mainly the locking of dislocations by first- and second-type segregations and the opposite effect of reorganization of the dislocation network. (Auth.)

Improving the prediction of the final part geometry in high strength steels U drawing by means of advanced material and friction models

Science.gov (United States)

de Argandoña, Eneko Saenz; Mendiguren, Joseba; Otero, Irune; Mugarra, Endika; Otegi, Nagore; Galdos, Lander

2018-05-01

Steel has been used in vehicles from the automotive industry's inception. Different steel grades are continually being developed in order to satisfy new fuel economy requirements. For example, advanced high strength steel grades (AHSS) are widely used due to their good strength/weight ratio. Because each steel grade has a different microstructure composition and hardness, they show different behaviors when they are subjected to different strain paths. Similarly, the friction behavior when using different contact pressures is considerably altered. In the present paper, four different steel grades, ZSt380, DP600, DP780 and Fortiform 1050 materials are deeply characterized using uniaxial and cyclic tension-compression tests. Coefficient of friction (COF) is also obtained using strip drawing tests. These results have been used to calibrate mixed kinematic-hardening material models as well as pressure dependent friction models. Finally, the geometrical accuracy of the different material and friction models has been evaluated by comparing the numerical predictions with experimental demonstrators obtained using a U-Drawing tester.

Segmentation-free empirical beam hardening correction for CT

Energy Technology Data Exchange (ETDEWEB)

Schüller, Sören; Sawall, Stefan [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich [Sirona Dental Systems GmbH, Fabrikstraße 31, 64625 Bensheim (Germany); Kachelrieß, Marc, E-mail: marc.kachelriess@dkfz.de [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

2015-02-15

Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the

Segmentation-free empirical beam hardening correction for CT.

Science.gov (United States)

Schüller, Sören; Sawall, Stefan; Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich; Kachelrieß, Marc

2015-02-01

The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the proposed

Effect of microstructure on static and dynamic mechanical properties of high strength steels

Science.gov (United States)

Qu, Jinbo

The high speed deformation behavior of a commercially available dual phase (DP) steel was studied by means of split Hopkinson bar apparatus in shear punch (25m/s) and tension (1000s-1) modes with an emphasis on the influence of microstructure. The cold rolled sheet material was subjected to a variety of heat treatment conditions to produce several different microstructures, namely ferrite plus pearlite, ferrite plus bainite and/or acicular ferrite, ferrite plus bainite and martensite, and ferrite plus different fractions of martensite. Static properties (0.01mm/s for shear punch and 0.001s -1 for tension) of all the microstructures were also measured by an MTS hydraulic machine and compared to the dynamic properties. The effects of low temperature tempering and bake hardening were investigated for some ferrite plus martensite microstructures. In addition, two other materials, composition designed as high strength low alloy (HSLA) steel and transformation induced plasticity (TRIP) steel, were heat treated and tested to study the effect of alloy chemistry on the microstructure and property relationship. A strong effect of microstructure on both static and dynamic properties and on the relationship between static and dynamic properties was observed. According to the variation of dynamic factor with static strength, three groups of microstructures with three distinct behaviors were identified, i.e. classic dual phase (ferrite plus less than 50% martensite), martensite-matrix dual phase (ferrite plus more than 50% martensite), and non-dual phase (ferrite plus non-martensite). Under the same static strength level, the dual phase microstructure was found to absorb more dynamic energy than other microstructures. It was also observed that the general dependence of microstructure on static and dynamic property relationship was not strongly influenced by chemical composition, except the ferrite plus martensite microstructures generated by the TRIP chemistry, which exhibited

On high temperature strength of carbon steels

International Nuclear Information System (INIS)

Ichinose, Hiroyuki; Tamura, Manabu; Kanero, Takahiro; Ihara, Yoshihito

1977-01-01

In the steels for high temperature use, the oxidation resistance is regarded as important, but carbon steels show enough oxidation resistance to be used continuously at the temperature up to 500 deg. C if the strength is left out of consideration, and up to 450 deg. C even when the strength is taken into account. Moreover, the production is easy, the workability and weldability are good, and the price is cheap in carbon steels as compared with alloy steels. In the boilers for large thermal power stations, 0.15-0.30% C steels are used for reheater tubes, main feed water tubes, steam headers, wall water tubes, economizer tubes, bypass pipings and others, and they account for 70% of all steel materials used for the boilers of 350 MW class and 30% in 1000 MW class. The JIS standard for the carbon steels for high temperature use and the related standards in foreign countries are shown. The high temperature strength of carbon steels changes according to the trace elements, melting and heat treatment as well as the main compositions of C, Si and Mn. Al and N affect the high temperature strength largely. The characteristics of carbon steels after the heating for hours, the factors controlling the microstructure and high temperature strength, and the measures to improve the high temperature strength of carbon steels are explained. (Kako, I.)

Skin hardening effect in patients with polymorphic light eruption: comparison of UVB hardening in hospital with a novel home UV-hardening device.

Science.gov (United States)

Franken, S M; Genders, R E; de Gruijl, F R; Rustemeyer, T; Pavel, S

2013-01-01

An effective prophylactic treatment of patients with polymorphic light eruption (PLE) consists of repeated low, gradually increasing exposures to UVB radiation. This so-called UV(B) hardening induces better tolerance of the skin to sunlight. SunshowerMedical company (Amsterdam) has developed an UV (B) source that can be used during taking shower. The low UV fluence of this apparatus makes it an interesting device for UV hardening. In a group of PLE patients, we compared the effectiveness of the irradiation with SunshowerMedical at home with that of the UVB treatment in the hospital. The PLE patients were randomized for one of the treatments. The hospital treatment consisted of irradiations with broad-band UVB (Waldmann 85/UV21 lamps) twice a week during 6 weeks. The home UV-device was used each day with the maximal irradiation time of 6 min. The outcome assessment was based on the information obtained from patients' dermatological quality of life (DLQI) questionnaires, the ability of both phototherapies to reduce the provocation reaction and from the patients' evaluation of the long-term benefits of their phototherapies. Sixteen patients completed treatment with SunshowerMedical and thirteen completed treatment in hospital. Both types of phototherapy were effective. There was a highly significant improvement in DLQI with either treatment. In most cases, the hardening reduced or even completely suppressed clinical UV provocation of PLE. The patients using SunshowerMedical at home were, however, much more content with the treatment procedure than the patients visiting the dermatological units. Both treatments were equally effective in the induction of skin tolerance to sunlight in PLE patients. However, the home treatment was much better accepted than the treatment in the hospital. © 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.

Influence of additives for concrete on the containment of radio-elements and strength under radiation of 'cement' matrices

International Nuclear Information System (INIS)

Pholvichith epouse Lezane, Ammala

1994-01-01

In order to improve the durability of cement-based materials used for the storage of radioactive wastes, fluidizers are generally introduced into these materials during their preparation. Thus, Naphtalene Sulfonate Formaldehyde (NSF) and Melamine Sulfonate Formaldehyde (MSF) are used as fluidizers in concrete which therefore presents good rheological properties when fresh, and a high compactness when hardened. This research study aims at investigating what happens to the fluidizer in a hardened cement paste, how this fluidizer affects the durability (mechanical strength, porosity, apparent diffusion coefficient) of a cement paste in absence of irradiation, what is the behaviour of these organic compounds under irradiation (reticulation or degradation, nature of radiolysis gases), how these organic compounds affects the durability (dimension, porosity, mechanical strength) of a cement paste under cobalt 60 gamma radiation, and how apparent solubilities of the different isotopes vary in cement water in presence of these organic compounds [fr

Instabilities in power law gradient hardening materials

DEFF Research Database (Denmark)

Niordson, Christian Frithiof; Tvergaard, Viggo

2005-01-01

Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...... of gradient hardening are found to delay the onset of localization under plane strain tension, and significantly reduce strain gradients in the localized zone. For plane strain compression gradient hardening is found to increase the load-carrying capacity significantly....

Optimum Compressive Strength of Hardened Sandcrete Building Blocks with Steel Chips

Directory of Open Access Journals (Sweden)

Alohan Omoregie

2013-02-01

Full Text Available The recycling of steel chips into an environmentally friendly, responsive, and profitable commodity in the manufacturing and construction industries is a huge and difficult challenge. Several strategies designed for the management and processing of this waste in developed countries have been largely unsuccessful in developing countries mainly due to its capital-intensive nature. To this end, this investigation attempts to provide an alternative solution to the recycling of this material by maximizing its utility value in the building construction industry. This is to establish their influence on the compressive strength of sandcrete hollow blocks and solid cubes with the aim of specifying the range percent of steel chips for the sandcrete optimum compressive strength value. This is particularly important for developing countries in sub-Saharan Africa, and even Latin America where most sandcrete blocks exhibit compressive strengths far below standard requirements. Percentages of steel chips relative to the weight of cement were varied and blended with the sand in an attempt to improve the sand grading parameters. The steel chips variations were one, two, three, four, five, ten and fifteen percent respectively. It was confirmed that the grading parameters were improved and there were significant increases in the compressive strength of the blocks and cube samples. The greatest improvement was noticed at four percent steel chips and sand combination. Using the plotted profile, the margin of steel chips additions for the optimum compressive strength was also established. It is recommended that steel chip sandcrete blocks are suitable for both internal load bearing, and non-load bearing walls, in areas where they are not subjected to moisture ingress. However, for external walls, and in areas where they are liable to moisture attack after laying, the surfaces should be well rendered. Below ground level, the surfaces should be coated with a water

Why semiconductors must be hardened when used in space

International Nuclear Information System (INIS)

Winokur, P.S.

2000-01-01

The natural space radiation environment presents a great challenge to present and future satellite systems with significant assets in space. Defining requirements for such systems demands knowledge about the space radiation environment and its effects on electronics and optoelectronics technologies, as well as suitable risk assessment of the uncertainties involved. For mission of high radiation levels, radiation-hardened integrated circuits will be required to preform critical mission functions. The most successful systems in space will be those that are best able to blend standard commercial electronics with custom radiation-hardened electronics in a mix that is suitable for the system of interest

Microstructural changes and strain hardening effects in abrasive contacts at different relative velocities and temperatures

Energy Technology Data Exchange (ETDEWEB)

Rojacz, H., E-mail: rojacz@ac2t.at [AC2T research GmbH, Viktor-Kaplan-Straße 2C, 2700 Wiener Neustadt (Austria); Mozdzen, G. [Aerospace & Advanced Composites GmbH, Viktor-Kaplan-Straße 2F, 2700 Wiener Neustadt (Austria); Weigel, F.; Varga, M. [AC2T research GmbH, Viktor-Kaplan-Straße 2C, 2700 Wiener Neustadt (Austria)

2016-08-15

Strain hardening is commonly used to reach the full potential of materials and can be beneficial in tribological contacts. 2-body abrasive wear was simulated in a scratch test, aimed at strain hardening effects in various steels. Different working conditions were examined at various temperatures and velocities. Strain hardening effects and microstructural changes were analysed with high resolution scanning electron microscopy (HRSEM), electron backscatter diffraction (EBSD), micro hardness measurements and nanoindentation. Statistical analysing was performed quantifying the influence of different parameters on microstructures. Results show a crucial influence of temperature and velocity on the strain hardening in tribological contacts. Increased velocity leads to higher deformed microstructures and higher increased surface hardness at a lower depth of the deformed zones at all materials investigated. An optimised surface hardness can be achieved knowing the influence of velocity (strain rate) and temperature for a “tailor-made” surface hardening in tribological systems aimed at increased wear resistance. - Highlights: •Hardening mechanisms and their intensity in tribological contacts are dependent on relative velocity and temperature. •Beneficial surface hardened zones are formed at certain running-in conditions; the scientific background is presented here. •Ferritic-pearlitic steels strain hardens via grain size reduction and decreasing interlamellar distances in pearlite. •Austenitic steels show excellent surface hardening (120% hardness increase) by twinning and martensitic transformation. •Ferritic steels with hard phases harden in the ferrite phase as per Hall-Petch equation and degree of deformation.

Microstructural changes and strain hardening effects in abrasive contacts at different relative velocities and temperatures

International Nuclear Information System (INIS)

Rojacz, H.; Mozdzen, G.; Weigel, F.; Varga, M.

2016-01-01

Strain hardening is commonly used to reach the full potential of materials and can be beneficial in tribological contacts. 2-body abrasive wear was simulated in a scratch test, aimed at strain hardening effects in various steels. Different working conditions were examined at various temperatures and velocities. Strain hardening effects and microstructural changes were analysed with high resolution scanning electron microscopy (HRSEM), electron backscatter diffraction (EBSD), micro hardness measurements and nanoindentation. Statistical analysing was performed quantifying the influence of different parameters on microstructures. Results show a crucial influence of temperature and velocity on the strain hardening in tribological contacts. Increased velocity leads to higher deformed microstructures and higher increased surface hardness at a lower depth of the deformed zones at all materials investigated. An optimised surface hardness can be achieved knowing the influence of velocity (strain rate) and temperature for a “tailor-made” surface hardening in tribological systems aimed at increased wear resistance. - Highlights: •Hardening mechanisms and their intensity in tribological contacts are dependent on relative velocity and temperature. •Beneficial surface hardened zones are formed at certain running-in conditions; the scientific background is presented here. •Ferritic-pearlitic steels strain hardens via grain size reduction and decreasing interlamellar distances in pearlite. •Austenitic steels show excellent surface hardening (120% hardness increase) by twinning and martensitic transformation. •Ferritic steels with hard phases harden in the ferrite phase as per Hall-Petch equation and degree of deformation.

The Effect of a Plasticizing Admixture on the Properties of Hardened Concrete

Directory of Open Access Journals (Sweden)

Anastasija Abasova

2012-11-01

Full Text Available Concrete is material obtained mixing matrix material, coarse and small aggregates and water along with additives acquiring necessary properties of hardening. The quality and properties of raw material used for manufacturing concrete, V/C ratio and the uniformity of the compaction of the mixture lead to the fundamental properties of concrete. The compressive strength of concrete is one of the most important properties of concrete. The article deals with the impact of plasticizers on the structural properties of concrete choosing an optimal content of additives. Concrete plasticizers increasing the content of additive increase the strength of samples, the density and ultrasonic pulse of velocity and decrease absorption. Test results have revealed that a plasticizing admixture under dosing or overdosing can reduce the properties of concrete.

Radiation hardenable coating mixture

International Nuclear Information System (INIS)

Howard, D.D.

1977-01-01

This invention relates to coatings that harden under radiation and to their compositions. Specifically, this invention concerns unsaturated urethane resins polymerisable by addition and to compositions, hardening under the effect of radiation, containing these resins. These resins feature the presence of at least one unsaturated ethylenic terminal group of structure CH 2 =C and containing the product of the reaction of an organic isocyanate compound with at least two isocyanate groups and one polyester polyol with at least two hydroxyl groups, and one unsaturated monomer compound polymerisable by addition having a single active hydrogen group reacting with the isocyanate [fr

Radiation hardening of oxygen-doped niobium by 14-MeV neutrons

International Nuclear Information System (INIS)

Bradley, E.R.; Jones, R.H.

1983-09-01

The flow properties of niobium containing 185 and 480 wt ppM oxygen have been studied following irradiation at 300K with T(d,n) neutrons to fluence levels ranging from 6 x 10 20 to 2 x 10 22 m -2 . Two hardening stages connected by a plateau region were observed in the niobium containing 185 wt ppM oxygen. Increasing the oxygen content by 300 wt ppM oxygen shifted the beginning of the high-fluence hardening stage from 6 x 10 21 to 1 x 10 21 m -2 , thereby eliminating the plateau region. This shift resulted in 1.5 times more hardening in the oxygen-doped niobium irradiated to fluence levels above 5 x 10 21 m -2

Strength Gain Properties up to five-year age of high-strength mass concrete

International Nuclear Information System (INIS)

Mitarai, Y.; Shigenobu, M.; Hiramine, T.; Inoue, K.; Nakane, S.; Ohike, T.

1991-01-01

Genkai No.3 plant of Kyushu Electric Power Co., Inc. presently under construction is a PWR type nuclear power plant with 1180 MW power output, and a prestressed concrete containment vessel (PCCV) was adopted for the reactor. The concrete used for the construction of the PCCV is the mass concrete with the wall thickness of 1.3 m in the general parts of the cylinder, and about 2 m at buttresses. It is the high strength concrete of the specified strength 420 kgf/cm 2 . As the preliminary study for the construction using such high strength mass concrete, the examination was carried out on the strength gain property of structural concrete using full scale simulated members. The various problems in the quality control were contemplated based on the results of the examination, and were reflected to actual construction, designating 13 weeks as the age for strength control, in order to build the concrete structures with high reliability. In this report, the outline of the study on the strength gain up to 5 year age carried out in the preliminary study is discussed. The experimental method, the method of evaluating structural strength, the mixing proportion of concrete and the results are reported. (K.I.)

High-strength concrete and the design of power plant structures

International Nuclear Information System (INIS)

Puttonen, J.

1991-01-01

Based on the literature, the design of high-strength concrete structures and the suitability of high-strength concrete for the power plant structures have been studied. Concerning the behavior of structures, a basic difference between the high-strength concrete and the traditional one is that the ductility of the high-strength concrete is smaller. In the design, the non-linear stress-strain relationship of the high-strength concrete has to be taken into account. The use of the high-strength concrete is economical if the strength of the material can be utilized. In the long term, the good durability and wear resistance of the high-strength concrete increases the economy of the material. Because of the low permeability of the high-strength concrete, it is a potential material in the safety-related structures of nuclear power plants. The study discovered no particular power plant structure which would always be economical to design of high-strength concrete. However, the high-strength concrete was found to be a competitive material in general

Update on radiation-hardened microcomputers for robotics and teleoperated systems

International Nuclear Information System (INIS)

Sias, F.R. Jr.; Tulenko, J.S.

1993-01-01

Since many programs sponsored by the Department of Defense are being canceled, it is important to select carefully radiation-hardened microprocessors for projects that will mature (or will require continued support) several years in the future. At the present time there are seven candidate 32-bit processors that should be considered for long-range planning for high-performance radiation-hardened computer systems. For Department of Energy applications it is also important to consider efforts at standardization that require the use of the VxWorks operating system and hardware based on the VMEbus. Of the seven processors, one has been delivered and is operating and other systems are scheduled to be delivered late in 1993 or early in 1994. At the present time the Honeywell-developed RH32, the Harris RH-3000 and the Harris RHC-3000 are leading contenders for meeting DOE requirements for a radiation-hardened advanced 32-bit microprocessor. These are all either compatible with or are derivatives of the MIPS R3000 Reduced Instruction Set Computer. It is anticipated that as few as two of the seven radiation-hardened processors will be supported by the space program in the long run

Development of a high temperature high strength Al alloy by addition of small amounts of Sc and Mg to 2219 alloy

Energy Technology Data Exchange (ETDEWEB)

Mondol, S. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Alam, T.; Banerjee, R. [Advanced Materials and Manufacturing Processes Institute and Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203-5017 (United States); Kumar, S. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Chattopadhyay, K., E-mail: kamanio@materials.iisc.ernet.in [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India)

2017-02-27

The paper reports a significant improvement in tensile properties, in particular at 200 °C, of commercial 2219 Al alloy by addition of small amounts of Sc (0.8 wt%) and Mg (0.45 wt%), and employing copper mould suction casting followed by natural ageing and cold rolling. Microstructural examination and measurement of hardness were performed in order to explain the effects of Sc and Mg at each processing step. It is found that the remarkable improvement of room temperature strength occurs due to fine grain size, Al{sub 3}Sc and Al{sub 3}(Sc,Zr) dispersoids, GP zones on {100} and {111} planes, and work hardening. On exposure at 200 °C, the GP zones transform primarily to θ′ precipitates and a few Ω precipitates. Sc and Mg atoms segregate at the θ′/matrix interface, which suppress the coarsening of θ′ precipitates and make them stable at higher temperatures. Thus, the work reports extremely high 0.2% proof stress of 542 MPa at room temperature, 378 MPa at 200 °C and 495 MPa at room temperature after 200 h exposure at 200 °C accompanied by reasonable ductility. Theoretical yield strength is calculated on the basis of the observed microstructure and is found to be in good agreement with the experimentally obtained value.

Development of a high temperature high strength Al alloy by addition of small amounts of Sc and Mg to 2219 alloy

International Nuclear Information System (INIS)

Mondol, S.; Alam, T.; Banerjee, R.; Kumar, S.; Chattopadhyay, K.

2017-01-01

The paper reports a significant improvement in tensile properties, in particular at 200 °C, of commercial 2219 Al alloy by addition of small amounts of Sc (0.8 wt%) and Mg (0.45 wt%), and employing copper mould suction casting followed by natural ageing and cold rolling. Microstructural examination and measurement of hardness were performed in order to explain the effects of Sc and Mg at each processing step. It is found that the remarkable improvement of room temperature strength occurs due to fine grain size, Al 3 Sc and Al 3 (Sc,Zr) dispersoids, GP zones on {100} and {111} planes, and work hardening. On exposure at 200 °C, the GP zones transform primarily to θ′ precipitates and a few Ω precipitates. Sc and Mg atoms segregate at the θ′/matrix interface, which suppress the coarsening of θ′ precipitates and make them stable at higher temperatures. Thus, the work reports extremely high 0.2% proof stress of 542 MPa at room temperature, 378 MPa at 200 °C and 495 MPa at room temperature after 200 h exposure at 200 °C accompanied by reasonable ductility. Theoretical yield strength is calculated on the basis of the observed microstructure and is found to be in good agreement with the experimentally obtained value.

Ultrahigh strength martensite–austenite dual-phase steels with ultrafine structure: The response to indentation experiments

International Nuclear Information System (INIS)

Misra, R.D.K.; Venkatsurya, P.; Wu, K.M.; Karjalainen, L.P.

2013-01-01

In medium to high carbon steels, characterized by martensite–austenite microstructure processed by quenching and partitioning process, martensite potentially provides high strength, while austenite provides work hardening [Fu, Wu, and Misra, DOI: 10.1179/1743284712/068]. Given the significant interest in these steels in the steel community, the paper reports for the first time the nanoscale deformation experiments and accompanying microstructural evolution to obtain micromechanical insights into the deformation behavior of ultrahigh strength-high ductility dual-phase steels with significant retained austenite fraction of ∼0.35. During deformation experiments with nanoindenter, dislocations were distributed on several slip systems, whereas strain-induced twinned martensite and twinning were the deformation mechanisms in carbon-enriched and thermally stabilized retained austenite. Furthermore, ultrafine dual-phase steels exhibited high strain rate sensitivity.

Ultrahigh strength martensite-austenite dual-phase steels with ultrafine structure: The response to indentation experiments

Energy Technology Data Exchange (ETDEWEB)

Misra, R.D.K., E-mail: dmisra@louisiana.edu [Laboratory for Excellence in Advanced Steel Research, Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504 (United States); Venkatsurya, P. [Laboratory for Excellence in Advanced Steel Research, Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504 (United States); Wu, K.M. [International Research Institute for Steel Technolgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Karjalainen, L.P. [Centre for Advanced Steels Research, University of Oulu, P.O. Box 4200, 90014 Oulu (Finland)

2013-01-10

In medium to high carbon steels, characterized by martensite-austenite microstructure processed by quenching and partitioning process, martensite potentially provides high strength, while austenite provides work hardening [Fu, Wu, and Misra, DOI: 10.1179/1743284712/068]. Given the significant interest in these steels in the steel community, the paper reports for the first time the nanoscale deformation experiments and accompanying microstructural evolution to obtain micromechanical insights into the deformation behavior of ultrahigh strength-high ductility dual-phase steels with significant retained austenite fraction of {approx}0.35. During deformation experiments with nanoindenter, dislocations were distributed on several slip systems, whereas strain-induced twinned martensite and twinning were the deformation mechanisms in carbon-enriched and thermally stabilized retained austenite. Furthermore, ultrafine dual-phase steels exhibited high strain rate sensitivity.

Effect of mixing methods and aggregate type on strength of hardened concrete

International Nuclear Information System (INIS)

Elhadi, S.

2006-01-01

The objective of the research contained in this paper is to study the effect on strength of concrete which can be caused by changing method of concrete mix with or without changing aggregate crushing value under hand or mechanical compaction, and to compare results obtained when nondestructive testing techniques are used. It has been found that all methods of mix design are nearly identical in predicting the strength under a known value of w/c ratio. Up to strength of about 30 N/mm 2 , hand and mechanical compaction seems to be identical in all methods of concrete mixing. Important results regarding destructive and non-destructive testing has been drawn from the study.(Author)

Copper alloys for high heat flux structure applications

International Nuclear Information System (INIS)

Zinkle, S.J.; Fabritsiev, S.A.

1994-01-01

The mechanical and physical properties of copper alloys are reviewed and compared with the requirements for high heat flux structural applications in fusion reactors. High heat flux structural materials must possess a combination of high thermal conductivity and high mechanical strength. The three most promising copper alloys at the present time are oxide dispersion-strengthened copper (Cu-Al 2 O 3 ) and two precipitation-hardened copper alloys (Cu-Cr-Zr and Cu-Ni-Be). These three alloys are capable of room temperature yield strengths >400 MPa and thermal conductivities up to 350 W/m-K. All of these alloys require extensive cold working to achieve their optimum strength. Precipitation-hardened copper alloys such Cu-Cr-Zr are susceptible to softening due to precipitate overaging and recrystallization during brazing, whereas the dislocation structure in Cu-Al 2 O 3 remains stabilized during typical high temperature brazing cycles. All three alloys exhibit good resistance to irradiation-induced softening and void swelling at temperatures below 300 degrees C. The precipitation-strengthened allows typically soften during neutron irradiation at temperatures above about 300 degrees C and therefore should only be considered for applications operating at temperatures 2 O 3 ) is considered to be the best candidate for high heat flux structural applications

SCC with high volume of fly ash content

Directory of Open Access Journals (Sweden)

Bakhrakh Anton

2017-01-01

Full Text Available Self-compacting concrete is a very perspective building material. It provides great benefits during the construction of heavily reinforced buildings. SCC has outstanding properties such as high flowability, dense structure and high strength due to specific quality of aggregates, fillers, their proportion in mix, use of polycarboxylate-based superplasticizers. Main disadvantages of SCC are high price and the difficulty of obtaining a proper mix. Use of fillers, such as fly ash type F, is a way to make SCC cheaper by replacing part of cement. Fly ash also provides some technological and operating advantages. In this paper the influence of high volume (60% from cement fly ash type F on the properties of concrete mixture and hardened concrete is investigated. The result of the work shows the possibility of reduction the cost of SCC using ordinary fillers and high amount of fly ash. The investigated SCC has low speed of hardening (7-day compressive strength at the range of 41.8 MPa and high volume of entrained air content (3.5%.

Quantitative analysis of artifacts in 4D DSA: the relative contributions of beam hardening and scatter to vessel dropout behind highly attenuating structures

Science.gov (United States)

Hermus, James; Szczykutowicz, Timothy P.; Strother, Charles M.; Mistretta, Charles

2014-03-01

When performing Computed Tomographic (CT) image reconstruction on digital subtraction angiography (DSA) projections, loss of vessel contrast has been observed behind highly attenuating anatomy, such as dental implants and large contrast filled aneurysms. Because this typically occurs only in a limited range of projection angles, the observed contrast time course can potentially be altered. In this work, we have developed a model for acquiring DSA projections that models both the polychromatic nature of the x-ray spectrum and the x-ray scattering interactions to investigate this problem. In our simulation framework, scatter and beam hardening contributions to vessel dropout can be analyzed separately. We constructed digital phantoms with large clearly defined regions containing iodine contrast, bone, soft issue, titanium (dental implants) or combinations of these materials. As the regions containing the materials were large and rectangular, when the phantoms were forward projected, the projections contained uniform regions of interest (ROI) and enabled accurate vessel dropout analysis. Two phantom models were used, one to model the case of a vessel behind a large contrast filled aneurysm and the other to model a vessel behind a dental implant. Cases in which both beam hardening and scatter were turned off, only scatter was turned on, only beam hardening was turned on, and both scatter and beam hardening were turned on, were simulated for both phantom models. The analysis of this data showed that the contrast degradation is primarily due to scatter. When analyzing the aneurysm case, 90.25% of the vessel contrast was lost in the polychromatic scatter image, however only 50.5% of the vessel contrast was lost in the beam hardening only image. When analyzing the teeth case, 44.2% of the vessel contrast was lost in the polychromatic scatter image and only 26.2% of the vessel contrast was lost in the beam hardening only image.

High-temperature plastic flow of a precipitation-hardened FeCoNiCr high entropy alloy

Energy Technology Data Exchange (ETDEWEB)

He, J.Y.; Wang, H.; Wu, Y.; Liu, X.J. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Nieh, T.G. [Department of Materials Science and Engineering, the University of Tennessee, Knoxville, TN 37996 (United States); Lu, Z.P., E-mail: luzhaoping@163.com [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

2017-02-16

In this work, we systematically investigated flow behavior of a high entropy alloy (HEA) strengthened by coherent γ′ precipitates in the temperature range of 1023–1173 K. In contrast to the single-phase FeCoNiCrMn HEA, this precipitate-hardened alloy, i.e., (FeCoNiCr){sub 94}Ti{sub 2}Al{sub 4}, exhibited large reduction of the steady-state strain rate (by ~2 orders of magnitude) or drastic enhancement in flow stress, indicating significant improvement in high-temperature properties. Our results showed that the deformation could be divided into two regimes. At temperatures below 1123 K, coherent γ′ precipitates effectively blocked the dislocation motion, thus resulted in a threshold stress effect. Above 1123 K, however, γ′ particles dissolved and the deformation was controlled by the ordinary dislocation climb mechanism. In addition, we conducted transmission electron microscopy to characterize dislocation-precipitate interaction to provide microstructural evidences to support our conclusion of the specific deformation mechanisms in the two temperature regimes.

Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

Energy Technology Data Exchange (ETDEWEB)

Onishi, Yasuo; Baer, Ellen BK; Chun, Jaehun; Yokuda, Satoru T.; Schmidt, Andrew J.; Sande, Susan; Buchmiller, William C.

2011-02-20

K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., 185 C, 10 hours) have been observed to form agglomerates with a shear strength up to 170 kPa. These high values were estimated by measured unconfined compressive strength (UCS) obtained with a pocket penetrometer. Due to its ease of use, it is anticipated that a pocket penetrometer will be used to acquire additional shear strength data from archived K-Basin sludge samples stored at the PNNL Radiochemical Processing Laboratory (RPL) hot cells. It is uncertain whether the pocket penetrometer provides accurate shear strength measurements of the material. To assess the bounding material strength and

Fatigue hardening and softening studies on strain hardened 18-8 austenitic stainless steel

International Nuclear Information System (INIS)

Ramakrishna Prasad, C.; Vasudevan, R.

1976-01-01

Metals when subjected to fatigue harden or soften depending on their previous mechanical history. Annealed or mildly cold worked metals are known to harden while severely cold worked metals soften when subjected to fatigue loading. In the present work samples of austenitic 18-8 steel cold worked to 11% and 22% reduction in area were mounted in a vertical pulsator and fatigued in axial tension-compression. Clear cut effects were produced and it was noticed that these depended on the extent of cold work, the amplitude as well as the number of cycles of fatigue and mean stress if any. (orig.) [de

Strength of 10CR-N martensitic steels

International Nuclear Information System (INIS)

Bahrami, F.; Hendry, A.

1993-01-01

10Cr stainless steel has been employed to examine the effect of nitrogen on microstructure and strength. Applying Solid state gaseous nitrogenising treatments a whole range of nitrogen martensite structures containing up to 0.45 wt% were obtained. It was found that a linear relationship exists between strength and nitrogen content in precipitate free martensitic structures. Yield strength increased from 705 to 1295 MPa for nitrogen free base material and alloys with 0.35 wt%N respectively. Pronounce secondary hardening was observed at a tempering temperature of 500 C. A linear relationship was also observed between the lattice parameter and nitrogen concentration in these alloys. A model for mechanical behaviour is presented. (orig.)

Mechanism of Secondary Hardening in Rapid Tempering of Dual-Phase Steel

Science.gov (United States)

Saha, Dulal Chandra; Nayak, Sashank S.; Biro, Elliot; Gerlich, Adrian P.; Zhou, Y.

2014-12-01

Dual-phase steel with ferrite-martensite-bainite microstructure exhibited secondary hardening in the subcritical heat affected zone during fiber laser welding. Rapid isothermal tempering conducted in a Gleeble simulator also indicated occurrence of secondary hardening at 773 K (500 °C), as confirmed by plotting the tempered hardness against the Holloman-Jaffe parameter. Isothermally tempered specimens were characterized by analytic transmission electron microscopy and high-angle annular dark-field imaging. The cementite (Fe3C) and TiC located in the bainite phase of DP steel decomposed upon rapid tempering to form needle-shaped Mo2C (aspect ratio ranging from 10 to 25) and plate-shaped M4C3 carbides giving rise to secondary hardening. Precipitation of these thermodynamically stable and coherent carbides promoted the hardening phenomenon. However, complex carbides were only seen in the tempered bainite and were not detected in the tempered martensite. The martensite phase decomposed into ferrite and spherical Fe3C, and interlath-retained austenite decomposed into ferrite and elongated carbide.

Extended Hall-Petch Relationships for Yield, Cleavage and Intergranular Fracture Strengths of bcc Steel and Its Deformation and Fracture Behaviors

Science.gov (United States)

Heo, N. H.; Heo, Y.-U.; Kwon, S. K.; Kim, N. J.; Kim, S.-J.; Lee, H.-C.

2018-03-01

Extended Hall-Petch relationships for yield ( σy ), cleavage ( σ_{cl} ) and intergranular fracture ( σ_{ig} ) strengths of pure iron have been established through the direct calculation of the proportional constant (k) and the estimation of the friction stress (σ0 ) . The magnitude orders of k and σ0 are generally ky causes the high work hardening rate.

A review of the stages of work hardening

Energy Technology Data Exchange (ETDEWEB)

Rollett, A.D.; Kocks, U.F.

1993-07-01

Stages of work hardening are reviewed with emphasis on links between each stage. Simple quantitative descriptions are given for each stage. Similarities between stage I, easy glide, and stage IV, large strain hardening, are pointed out both in terms of magnitude of the hardening rate and of the underlying mechanism of dislocation debris accumulation. Stage II is described as an athermal hardening stage that occurs when statistical variations in the dislocation ``forest`` lead to geometrical storage of dislocations. The steadily decreasing hardening rate observed in stage III is characterized by the increasing rate of loss of dislocation density due to dynamic recovery. Stage III appears to have an asymptote to a saturation stress which is determined by the characteristics of the dislocation tangles, or cell walls. The imperfect nature of the dynamic recovery process, however, leads to the accumulation of dislocation debris and this, by analogy with stage 1, causes the apparent saturation stress to rise, thus causing stage IV.

Radiation Hardened Ethernet PHY and Switch Fabric, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Innoflight will develop a new family of radiation hardened (up to 3 Mrad(Si)), fault-tolerant, high data-rate (up to 8 Gbps), low power Gigabit Ethernet PHY and...

Atomistic study of the hardening of ferritic iron by Ni-Cr decorated dislocation loops

Science.gov (United States)

Bonny, G.; Bakaev, A.; Terentyev, D.; Zhurkin, E.; Posselt, M.

2018-01-01

The exact nature of the radiation defects causing hardening in reactor structural steels consists of several components that are not yet clearly determined. While generally, the hardening is attributed to dislocation loops, voids and secondary phases (radiation-induced precipitates), recent advanced experimental and computational studies point to the importance of solute-rich clusters (SRCs). Depending on the exact composition of the steel, SRCs may contain Mn, Ni and Cu (e.g. in reactor pressure vessel steels) or Ni, Cr, Si, Mn (e.g. in high-chromium steels for generation IV and fusion applications). One of the hypotheses currently implied to explain their formation is the process of radiation-induced diffusion and segregation of these elements to small dislocation loops (heterogeneous nucleation), so that the distinction between SRCs and loops becomes somewhat blurred. In this work, we perform an atomistic study to investigate the enrichment of loops by Ni and Cr solutes and their interaction with an edge dislocation. The dislocation loops decorated with Ni and Cr solutes are obtained by Monte Carlo simulations, while the effect of solute segregation on the loop's strength and interaction mechanism is then addressed by large scale molecular dynamics simulations. The synergy of the Cr-Ni interaction and their competition to occupy positions in the dislocation loop core are specifically clarified.

Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel

International Nuclear Information System (INIS)

Huang, Zhi Yong; Chaboche, Jean-Louis; Wang, Qing Yuan; Wagner, Danièle; Bathias, Claude

2014-01-01

Carbon–manganese steel A48 (French standard) is used in steam generator pipes of nuclear reactor pressure vessels at high temperatures (about 200 °C). The steel is sensitive to dynamic strain aging in monotonic tensile test and low cycle fatigue test at certain temperature range and strain rate. Its isotropic hardening behavior observed from experiments has a hardening, softening and hardening evolution with the effect of dynamic strain aging. The isotropic hardening model is improved by coupling the dislocation and dynamic strain aging theory to describe the behavior of A48 at 200 °C

Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel

Energy Technology Data Exchange (ETDEWEB)

Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Chaboche, Jean-Louis [ONERA, DMSM, 29 avenue de la Division Lecerc, F-92320 Chatillon (France); Wang, Qing Yuan [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle; Bathias, Claude [Université ParisOuest Nanterre La Défense (France)

2014-01-01

Carbon–manganese steel A48 (French standard) is used in steam generator pipes of nuclear reactor pressure vessels at high temperatures (about 200 °C). The steel is sensitive to dynamic strain aging in monotonic tensile test and low cycle fatigue test at certain temperature range and strain rate. Its isotropic hardening behavior observed from experiments has a hardening, softening and hardening evolution with the effect of dynamic strain aging. The isotropic hardening model is improved by coupling the dislocation and dynamic strain aging theory to describe the behavior of A48 at 200 °C.

Radiation-hardened bulk Si-gate CMOS microprocessor family

International Nuclear Information System (INIS)

Stricker, R.E.; Dingwall, A.G.F.; Cohen, S.; Adams, J.R.; Slemmer, W.C.

1979-01-01

RCA and Sandia Laboratories jointly developed a radiation-hardened bulk Si-gate CMOS technology which is used to fabricate the CDP-1800 series microprocessor family. Total dose hardness of 1 x 10 6 rads (Si) and transient upset hardness of 5 x 10 8 rads (Si)/sec with no latch up at any transient level was achieved. Radiation-hardened parts manufactured to date include the CDP-1802 microprocessor, the CDP-1834 ROM, the CDP-1852 8-bit I/O port, the CDP-1856 N-bit 1 of 8 decoder, and the TCC-244 256 x 4 Static RAM. The paper is divided into three parts. In the first section, the basic fundamentals of the non-hardened C 2 L technology used for the CDP-1800 series microprocessor parts is discussed along with the primary reasons for hardening this technology. The second section discusses the major changes in the fabrication sequence that are required to produce radiation-hardened devices. The final section details the electrical performance characteristics of the hardened devices as well as the effects of radiation on device performance. Also included in this section is a discussion of the TCC-244 256 x 4 Static RAM designed jointly by RCA and Sandia Laboratories for this application

Contributions of Cu-rich clusters, dislocation loops and nanovoids to the irradiation-induced hardening of Cu-bearing low-Ni reactor pressure vessel steels

Science.gov (United States)

Bergner, F.; Gillemot, F.; Hernández-Mayoral, M.; Serrano, M.; Török, G.; Ulbricht, A.; Altstadt, E.

2015-06-01

Dislocation loops, nanovoids and Cu-rich clusters (CRPs) are known to represent obstacles for dislocation glide in neutron-irradiated reactor pressure vessel (RPV) steels, but a consistent experimental determination of the respective obstacle strengths is still missing. A set of Cu-bearing low-Ni RPV steels and model alloys was characterized by means of SANS and TEM in order to specify mean size and number density of loops, nanovoids and CRPs. The obstacle strengths of these families were estimated by solving an over-determined set of linear equations. We have found that nanovoids are stronger than loops and loops are stronger than CRPs. Nevertheless, CRPs contribute most to irradiation hardening because of their high number density. Nanovoids were only observed for neutron fluences beyond typical end-of-life conditions of RPVs. The estimates of the obstacle strength are critically compared with reported literature data.

Elastic stability and the limit of strength

International Nuclear Information System (INIS)

Morris Jr., J.W.; Krenn, C.R.; Roundy, D.; Cohen, Marvin L.

2002-01-01

The upper limit of strength (the ''theoretical strength'') has been an active subject of research and speculation for the better part of a century. The subject has recently become important, for two reasons. First, given recent advances in ab initio techniques and computing machines, the limits of strength can be calculated with considerable accuracy, making this one of the very few problems in mechanical behavior that can actually be solved. Second, given recent advances in materials engineering, the limits of strength are being approached in some systems, such as hardened or defect-free films, and their relevance is becoming recognized in others. The present paper discusses some interesting results from recent research on the limits of strength, with an intermixture of speculations based on those results. Topics include the inherent nature of {100} cleavage and ''pencil slip'' in bcc metals, the inherent ductility of fcc metals, the anomalous properties of Al, and the possibility of measuring ideal strength with nanoindentation

Yield strength of a heavily drawn Cu-20% Nb filamentary microcomposite

International Nuclear Information System (INIS)

Hong, S.I.

1998-01-01

It has been well documented that heavily-drawn, copper-niobium microcomposites possess high strength and high conductivity. Since niobium has little solubility in copper, the conductivity of the copper is not strongly affected by the addition of niobium. Following extensive mechanical deformation of Cu-Nb, niobium dendrites transform into fine niobium ribbons as a result of the niobium texture upon drawing. This nanostructure contributes to the ultrahigh strength of Cu-Nb microcomposites. The strength of heavily deformed Cu-Nb exceeds that predicted by the rule-of-mixtures (ROM), and a fundamental understanding of the strengthening mechanisms involved has been the subject of much discussion. Spitzig and his coworkers suggests a barrier strengthening model while Funkenbusch and Courtney believe that stored dislocations have a role in substructural hardening. Hangen and Raabe recently proposed an analytical model for the calculation of the yield strength of Cu-Nb microcomposite. The model of Hangen and Raabe and that of Spitzig and his coworkers have a great deal of resemblance since both models attribute the strength to the difficulty of propagating plastic flow through the interface. The purpose of this study was to enhance the understanding of the strengthening mechanisms associated with Cu-Nb microcomposites by examining the previous studies on mechanical and microstructural stability of Cu-based microcomposites

The use of microhardness tests to determine the radiation hardening of austenitic stainless steel; Zastosowanie pomiarow mikrotwardosci dla okreslenia umocnienia radiacyjnego stali austenitycznej napromienionej neutronami

Energy Technology Data Exchange (ETDEWEB)

Hofman, A.; Kochanski, T.; Malczyk, A.

1994-12-31

The use of microhardness technique to determine the radiation hardening has been studied. Microhardness measurements have been conducted on austenitic stainless steel OH18N1OT irradiated up to 2x10{sup 19} ncm{sup -2}. It was determined that the increase in microhardness varies directly with the measured increase in the 0.2% offset yield strength and has been found that microhardness technique may be an effective tool to measurements of radiation induced hardening. (author). 18 refs, 3 figs, 3 tabs.

Structural integrity of stainless steel components exposed to neutron irradiation. Change in failure strength of cracked components due to cold working

International Nuclear Information System (INIS)

Kamaya, Masayuki; Hojo, Tomohiro; Mochizuki, Masahito

2015-01-01

Load carrying capacity of austenitic stainless steel component is increased due to hardening caused by neutron irradiation if no crack is included in the component. On the other hand, if a crack is initiated in the reactor components, the hardening may decrease the load carrying capacity due to reduction in fracture toughness. In this paper, in order to develop a failure assessment procedure of irradiated cracked components, characteristics of change in failure strength of stainless steels due to cold working were investigated. It was experimentally shown that the proof and tensile strengths were increased by the cold working, whereas the fracture toughness was decreased. The fracture strengths of a cylinder with a circumferential surface crack were analyzed using the obtained material properties. Although the cold working altered the failure mode from plastic collapse to the unsteady ductile crack growth, it did not reduce failure strengths even if 50% cold working was applied. The increase in failure strength was caused not only by increase in flow stress but also by reduction in J-integral value, which was brought by the change in stress-strain curve. It was shown that the failure strength of the hardened stainless steel components could be derived by the two-parameter method, in which the change in material properties could be reasonably considered. (author)

Space Qualified, Radiation Hardened, Dense Monolithic Flash Memory, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Radiation hardened nonvolatile memories for space is still primarily confined to EEPROM. There is high density effective or cost effective NVM solution available to...

Investigation of a Hardened Cement Paste Grout

DEFF Research Database (Denmark)

Esteves, Luis Pedro; Sørensen, Eigil Verner

This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....

Calculation of calcium diffusion coefficient of cement hardenings using minute pore data

International Nuclear Information System (INIS)

Hitomi, Takashi; Takeda, Nobufumi; Iriya, Keishiro

2009-01-01

This report describes the calculations of the diffusion coefficient of the Ca ion of cement hardenings using minute pore data. The observed hardenings were ordinary Portland cement (OPC), low-heat Portland cement with fly ash (LPC+FA) and highly fly ash containing silica fume cement (HFSC). The samples were cured in the standard and artificially leached by accelerated test. Minute pore datas of the cement hardenings were acquired with image processing of internal structural information obtained from high resolution X-ray computed tomography observations. Upon analysis, several voxels are combined into one bigger voxel, the diffusion coefficient of the voxels were determined in proportion to the number of voxels which were included in. The results reveal that the change in the calcium diffusion coefficient of OPC due to leaching was large, but the LPC+FA and HFSC cements exhibited even greater changes than OPC. It is suggested that the diffusion coefficients are proportional to the Ca/Si ratio of the samples. (author)

Microstructure, cold workability and strain hardening behavior of trimodaled AA 6061-TiO2 nanocomposite prepared by mechanical alloying

International Nuclear Information System (INIS)

Sivasankaran, S.; Sivaprasad, K.; Narayanasamy, R.

2011-01-01

Highlights: → Trimodaled composites consisting of UFG and CG matrix phases and ceramic phase were produced successfully. → Cold deformation behavior was investigated. → The 15% CG trimodaled composite yielded a high compressive strength of 935 MPa. → The 30% CG composite exhibited higher ductility while maintaining strength and toughness. - Abstract: In the present work, the improvement of compressive ductility while maintaining high strength and toughness for nanocrystalline materials by cold upsetting (incremental loads) of bulk trimodaled composite was studied. Mechanically alloyed nanocrystalline (NC) AA 6061 alloy powders reinforced with nano TiO 2 were blended with 0, 5, 10, 15, 20, 25, and 30 wt.% coarse grain (CG) elemental powders related to AA 6061 alloy composition to produce trimodal microstructure. The synthesized composite preforms were characterized by optical microscope, scanning electron microscope, transmission electron microscope and X-ray diffraction. The room temperature compressive deformation behavior was evaluated under triaxial stress state condition. With increasing percentage of CG phase in the nanocomposite, the gradual improvement in compressive ductility was observed at the cost of a small amount of strength but it favored the ease of deformation. The 15% CG trimodal composite exhibited an extremely high compressive strength of 935 MPa due to non-coalescence of individual CG particles and effective load transfer occurred in multi scale microstructures. But the 30% CG trimodal composite showed an incremental compressive ductility of around 16% while sacrificing a small amount of strength (845 MPa) and this composite displayed improved toughness (area under true effective stress and true effective strain curve) of over 600% than nanocomposite (0% CG). Also, the percentage cold workability of 30% CG composite was six times higher than that of 0% CG composite. Hence, the 30% CG trimodal composite was observed to be the good one as

The application and processing of paints hardened by electron beams

International Nuclear Information System (INIS)

Anon.

1984-01-01

Electron beam hardening is a process for changing liquid surface coatings of different thicknesses by irradiation with electrons of high energy into solid, hard, elastic films. In contrast to the UV process, one can harden pigmented paints with electron beams. An electron accelerator, which remits free electrons is used as the energy source for starting the chemical reaction in the coating material. In order to irradiate flat parts, which were coated with liquid paint by rolling, pouring or spraying, equally with electrons, one must produce an 'electron curtain', similar to that in a paint pouring machine. (orig./PW) [de

Microstructure and properties of cast iron after laser surface hardening

Directory of Open Access Journals (Sweden)

Stanislav

2013-12-01

Full Text Available Laser surface hardening of cast iron is not trivial due to the material’s heterogeneity and coarse-grained microstructure, particularly in massive castings. Despite that, hardening of heavy moulds for automotive industry is in high demand. The present paper summarises the findings collected over several years of study of materials structure and surface properties. Phase transformations in the vicinity of graphite are described using examples from production of body parts in automotive industry. The description relates to formation of martensite and carbide-based phases, which leads to hardness values above 65 HRC and to excellent abrasion resistance.

Maillard-reaction-induced modification and aggregation of proteins and hardening of texture in protein bar model systems.

Science.gov (United States)

Zhou, Peng; Guo, Mufan; Liu, Dasong; Liu, Xiaoming; Labuza, Teodore P

2013-03-01

The hardening of high-protein bars causes problems in their acceptability to consumers. The objective of this study was to determine the progress of the Maillard reaction in model systems of high-protein nutritional bars containing reducing sugars, and to illustrate the influences of the Maillard reaction on the modification and aggregation of proteins and the hardening of bar matrices during storage. The progress of the Maillard reaction, glycation, and aggregation of proteins, and textural changes in bar matrices were investigated during storage at 25, 35, and 45 °C. The initial development of the Maillard reaction caused little changes in hardness; however, further storage resulted in dramatic modification of protein with formation of high-molecular-weight polymers, resulting in the hardening in texture. The replacement of reducing sugars with nonreducing ingredients such as sugar alcohols in the formula minimized the changes in texture. The hardening of high-protein bars causes problems in their acceptability to consumers. Maillard reaction is one of the mechanisms contributing to the hardening of bar matrix, particularly for the late stage of storage. The replacement of reducing sugars with nonreducing ingredients such as sugar alcohols in the formula will minimize the changes in texture. © 2013 Institute of Food Technologists®

Hardening and softening analysis of pure titanium based on the dislocation density during torsion deformation

Energy Technology Data Exchange (ETDEWEB)

Chen, Han; Li, Fuguo, E-mail: fuguolx@nwpu.edu.cn; Li, Jinghui; Ma, Xinkai; Li, Jiang; Wan, Qiong

2016-08-01

The hardening and softening phenomena during torsion deformation are studied based on the Taylor dislocation model for pure titanium. The hardening and softening phenomena are observed through the hardness analysis during micro-indentation test and micro-hardness test. Besides, the variations of indentation size also verify the existence of hardening and softening phenomena during torsion. The variations of geometric necessary dislocations (GNDs) and statistic store dislocations (SSDs) state that the positions of high dislocation density and low dislocation density correspond to the positions of hardening and softening. The results from the microstructure, grain boundaries evolution and twins analysis indicate the twins play an important role in appearance of hardening and softening phenomena. The appearance of hardening and softening phenomena are attributed to the combination of different slip systems and twinning systems combining with the Schmid Factor (SF) analysis and the transmission electron microscope (TEM). The appearance of hardening and softening phenomena can be explained by the Taylor dislocation theory based on TEM analysis. - Highlights: • The phenomena can be characterized by Taylor dislocation model. • The variation of GNDs leads to the phenomena. • The phenomena are proved by micro-hardness, indentation hardness. • The {10-12} twin and {11-24} twin play an important role in the phenomena.

Changes in Structural Characteristics of Hypoeutectic Al-Si Cast Alloy after Age Hardening

OpenAIRE

Lenka HURTALOVÁ; Juraj BELAN; Eva TILLOVÁ; Mária CHALUPOVÁ

2012-01-01

The contribution describes influence of the age-hardening consist of solution treatment at 515 °C with holding time 4 hours, water quenching at 40 °C and artificial aging at different temperature 150 °C, 170 °C and 190 °C with different holding time 2, 4, 8, 16 and 32 hours on mechanical properties (tensile strength and Brinell hardness) and changes in morphology of eutectic Si, Fe-rich and Cu-rich intermetallic phases in secondary (recycled) AlSi9Cu3 cast alloy. A combination of different an...

Comparison and Analysis of Steel Frame Based on High Strength Column and Normal Strength Column

Science.gov (United States)

Liu, Taiyu; An, Yuwei

2018-01-01

The anti-seismic performance of high strength steel has restricted its industrialization in civil buildings. In order to study the influence of high strength steel column on frame structure, three models are designed through MIDAS/GEN finite element software. By comparing the seismic performance and economic performance of the three models, the three different structures are comprehensively evaluated to provide some references for the development of high strength steel in steel structure.

Methods for improving weld strength of two-phase titanium alloys

International Nuclear Information System (INIS)

Zamkov, V.N.; Kushnirenko, N.A.; Topol'ski , V.F.; Khorev, A.I.

1980-01-01

The methods for improving the strength and impact toughness of welded joints of two-phase α+β martensitic titanium alloys (VT14, VT6, VT6S, VT23, VT22) are discussed. Thermal hardening of of welded joints under conditions recommended for the basic metal is shown to lead to the decrease of their ductibility. It has been established that the high quality of welded joints is obtained by the usage of the additional wire of Ti-Al-Mo-V-Nb-Zr-Re system in heat treatment under optimum conditions, in particular, after the low-temperature aging

Numerical and experimental comparison of plastic work-hardening rules

International Nuclear Information System (INIS)

Haisler, W.E.

1977-01-01

The purpose of this paper is to describe recent numerical and experimental correlation studies of several plastic work-hardening rules. The mechanical sublayer model and the combined kinematic-isotropic hardening rules are examined and the numerical results for several structural geometries are compared to experimental results. Both monotonic and cyclic loads are considered. The governing incremental plasticity relations are developed for both work-hardening models. The combined kinematic-isotropic hardening model is developed in terms of a ratio γ which controls the relative contribution of kinematic hardening (yield surface translation) and isotropic hardening (yield surface expansion). In addition to making use of a uniaxial stress-strain curve as input data, the model allows for the input of a yield surface size vs. uniaxial plastic strain curve obtained from a cyclic uniaxial reverse loading test. The mechanical sublayer model is developed in general form and a new method for determining the sublayer parameters (stress weighting factors and yield stresses) is presented. It is demonstrated that former procedures used to obtain the sublayer parameters are inconsistent for multiaxial loading. Numerical and experimental results are presented for a cylinder, circular plate with punch, and a steel pressure vessel. The numerical results are obtained with the computer program AGGIE I. The comparison study indicates that reasonable agreement is obtained with both hardening models; the choice depending upon whether the loading is monotonic or cyclic

Effect of Annealing on Microstructures and Hardening of Helium-Hydrogen-Implanted Sequentially Vanadium Alloys

Science.gov (United States)

Jiang, Shaoning; Wang, Zhiming

2018-03-01

The effect of post-irradiation annealing on the microstructures and mechanical properties of V-4Cr-4Ti alloys was studied. Helium-hydrogen-irradiated sequentially V-4Cr-4Ti alloys at room temperature (RT) were undergone post-irradiation annealing at 450 °C over periods of up to 30 h. These samples were carried out by high-resolution transmission electron microscopy (HRTEM) observation and nanoindentation test. With the holding time, large amounts of point defects produced during irradiation at RT accumulated into large dislocation loops and then dislocation nets which promoted the irradiation hardening. Meanwhile, bubbles appeared. As annealing time extended, these bubbles grew up and merged, and finally broke up. In the process, the size of bubbles increased and the number density decreased. Microstructural changes due to post-irradiation annealing corresponded to the change of hardening. Dislocations and bubbles are co-contributed to irradiation hardening. With the holding time up to 30 h, the recovery of hardening is not obvious. The phenomenon was discussed by dispersed barrier hardening model and Friedel-Kroupa-Hirsch relationship.

Slippage of steel in high and normal strength concrete

International Nuclear Information System (INIS)

Ahmed, K.; Siddiqi, Z.A.; Yousaf, M.

2007-01-01

Composite action of any reinforced concrete member is only possible if sufficient bond strength exists between steel reinforcing bars and concrete, which can adequately transfer shear stress between them. Bond strength is a function of compressive strength of concrete and hence high strength concrete has higher bond strength (1-2). Therefore required development length can be reduced. In order to investigate the effect of development length on bond stress and slip relationships, experimental investigation was carried out. In this experimentation 24 pull-out samples of high strength concrete and normal strength concrete were casted and tested. The results of this investigation revealed that by increasing the development length from 5db to 10db bond strength increases for both high and normal strength concrete as shown in Figure 11, 12 and 13. However in case of normal strength concrete increase in bond strength is more compared to that in high strength concrete as it is clear from Figure 11 and Figure 13. The increase in bond strength is observed even at 10db development length but the extent is less for 19 mm than 16 mm bars as shown in Figure 12 and Figure 13. This is in agreement with the earlier findings of Chen et al (3) and Harajli et al (1). However in case of HSC the total slippage at 10db is 50% greater than at 5db. This may be due to the fact that more no of concrete keys participate in resisting the slippage. (author)

Evaluation of Bending Strength of Carburized Gears Based on Inferential Identification of Principal Surface Layer Defects

Science.gov (United States)

Masuyama, Tomoya; Inoue, Katsumi; Yamanaka, Masashi; Kitamura, Kenichi; Saito, Tomoyuki

High load capacity of carburized gears originates mainly from the hardened layer and induced residual stress. On the other hand, surface decarburization, which causes a nonmartensitic layer, and inclusions such as oxides and segregation act as latent defects which considerably reduce fatigue strength. In this connection, the authors have proposed a formula of strength evaluation by separately quantifying defect influence. However, the principal defect which limits strength of gears with several different defects remains unclarified. This study presents a method of inferential identification of principal defects based on test results of carburized gears made of SCM420 clean steel, gears with both an artificial notch and nonmartensitic layer at the tooth fillet, and so forth. It clarifies practical uses of presented methods, and strength of carburized gears can be evaluated by focusing on principal defect size.

On the calibration strategies of the Johnson–Cook strength model: Discussion and applications to experimental data

International Nuclear Information System (INIS)

Gambirasio, Luca; Rizzi, Egidio

2014-01-01

The present paper aims at assessing the various procedures adoptable for calibrating the parameters of the so-called Johnson–Cook strength model, expressing the deviatoric behavior of elastoplastic materials, with particular reference to the description of High Strain Rate (HSR) phenomena. The procedures rely on input experimental data corresponding to a set of hardening functions recorded at different equivalent plastic strain rates and temperatures. After a brief review of the main characteristics of the Johnson–Cook strength model, five different calibration strategies are framed and widely described. The assessment is implemented through a systematic application of each calibration strategy to three different real material cases, i.e. a DH-36 structural steel, a commercially pure niobium and an AL-6XN stainless steel. Experimental data available in the literature are considered. Results are presented in terms of plots showing the predicted Johnson–Cook hardening functions against the experimental trends, together with tables describing the fitting problematics which arise in each case, by assessing both lower yield stress and overall plastic flow introduced errors. The consequences determined by each calibration approach are then carefully compared and evaluated. A discussion on the positive and negative aspects of each strategy is presented and some suggestions on how to choose the best calibration approach are outlined, by considering the available experimental data and the objectives of the following modeling process. The proposed considerations should provide a useful guideline in the process of determining the best Johnson–Cook parameters in each specific situation in which the model is going to be adopted. A last section introduces some considerations about the calibration of the Johnson–Cook strength model through experimental data different from those consisting in a set of hardening functions relative to different equivalent plastic strain

Hardening in AlN induced by point defects

International Nuclear Information System (INIS)

Suematsu, H.; Mitchell, T.E.; Iseki, T.; Yano, T.

1991-01-01

Pressureless-sintered AIN was neutron irradiated and the hardness change was examined by Vickers indentation. The hardness was increased by irradiation. When the samples were annealed at high temperature, the hardness gradually decreased. Length was also found to increase and to change in the same way as the hardness. A considerable density of dislocation loops still remained, even after the hardness completely recovered to the value of the unirradiated sample. Thus, it is concluded that the hardening in AIN is caused by isolated point defects and small clusters of point defects, rather than by dislocation loops. Hardness was found to increase in proportion to the length change. If the length change is assumed to be proportional to the point defect density, then the curve could be fitted qualitatively to that predicted by models of solution hardening in metals. Furthermore, the curves for three samples irradiated at different temperatures and fluences are identical. There should be different kinds of defect clusters in samples irradiated at different conditions, e.g., the fraction of single point defects is the highest in the sample irradiated at the lowest temperature. Thus, hardening is insensitive to the kind of defects remaining in the sample and is influenced only by those which contribute to length change

COMPLEX SURFACE HARDENING OF STEEL ARTICLES

Directory of Open Access Journals (Sweden)

A. V. Kovalchuk

2014-01-01

Full Text Available The method of complex surface hardening of steel detailswas designed. The method is a compound of two processes of hardening: chemical heat treatment and physical vapor deposition (PVD of the coating. The result, achieved in this study is much higher, than in other work on this topic and is cumulative. The method designed can be used in mechanical engineering, medicine, energetics and is perspective for military and space technologies.

Effect of combined addition of N and Nb on the high temperature behavior of a 25Cr-20Ni stainless steel

International Nuclear Information System (INIS)

Park, In Duck; Nam, Ki Woo

2002-01-01

In order to clarify the effect of precipitates on creep strength at high temperature in 25Cr-20Ni stainless steels, threshold stress and void-hardening stress have been measured and compared each others. The value of threshold stress for high temperature, measured by stress abruptly loading test, is about 130 MPa. Threshold stress must be measured by the function of stress loading time in the combination hardening steel of solution hardening and precipitate hardening. Average diameter and inter-partial distance of precipitates from TEM microstructure can determine void-hardening stress. The value of void-hardening stress, evaluated by using Scattergood and Bacon's equation, was from 101 to 130 MPa. The ratio of average void hardening to threshold stress is 1.13 and both values are not equal. The result from analyzing the electron diffraction pattern shows that the dispersed precipitates in SUS310J1TB is NbCrN nitrides. Mechanism of the interaction between dislocations and precipitate particles in SUS310J1TB is Srolovitz mechanism, which is a gravitation-type interaction

The possibility of using high strength reinforced concrete

International Nuclear Information System (INIS)

Miura, Nobuaki

1991-01-01

There is recently much research about and developments in reinforced concrete using high strength concrete and reinforcement. As a result, some high-rise buildings and nuclear buildings have been constructed with such concrete. Reinforced concrete will be stronger in the future, but there is a limit to its strength defined by the character of the materials and also by the character of the reinforced concrete members made of the concrete and reinforcement. This report describes the merits and demerits of using high strength reinforced concrete. (author)

Comparison of the irradiation effects on swelling and microstructure in commercial alloy A-286 and a simple Fe--25 Ni--15Cr gamma prime hardened alloy

International Nuclear Information System (INIS)

Chickering, R.W.; Bajaj, R.; Lally, J.S.

1977-01-01

The irradiation behaviors of alloy A-286 as well as experimental gamma prime hardened alloys are being studied in the National Alloy Development Program for application of gamma prime hardened alloys in the liquid metal fast breeder reactor. The principal direction of the studies concerns the high temperature strength and swelling resistance of the alloys. Minor element compositions may affect the phase stability and void swelling. A high Ti to Al ratio indicates a tendency for the gamma prime Ni 3 (Ti,Al) to transform into eta phase (Ni 3 Ti) after long term thermal aging and irradiation enhances the tendency for transformation. Another minor element, Si, as a constituent of G-phase, and irradiation may enhance G-phase formation. The Ti, Al, and Si contents affect the swelling of Fe-Cr-Ni alloys. The swelling resistance generally increases with increasing amounts of these three elements in the matrix. In the study the effects of Ti to Al ratio, Ti content, Al content, and Si content on swelling and phase stability were analyzed after Ni-ion irradiation

Induction surface hardening of hard coated steels

Energy Technology Data Exchange (ETDEWEB)

Pantleon, K.; Kessler, O.; Hoffann, F.; Mayr, P. [Stiftung Inst. fuer Werkstofftechnik, Bremen (Germany)

1999-11-01

The properties of hard coatings deposited using CVD processes are usually excellent. However, high deposition temperatures negatively influence the substrate properties, especially in the case of low alloyed steels. Therefore, a subsequent heat treatment is necessary to restore the properties of steel substrates. Here, induction surface hardening is used as a method of heat treatment after the deposition of TiN hard coatings on AISI 4140 (DIN42CrMo4) substrates. The influences of the heat treatment on both the coating and the substrate properties are discussed in relation to the parameters of induction heating. Thereby, the heating time, heating atmosphere and the power input into the coating-substrate compounds are varied. As a result of induction surface hardening, the properties of the substrates are improved without losing good coating properties. High hardness values in the substrate near the interface allow the AISI 4140 substrates to support TiN hard coatings very well. Consequently, higher critical loads are measured in scratch tests after the heat treatment. Also, compressive residual stresses in the substrate are generated. In addition, only a very low distortion appears. (orig.)

Hardening of niobium alloys at precrystallization annealing

International Nuclear Information System (INIS)

Vasil'eva, E.V.; Pustovalov, V.A.

1989-01-01

Niobium base alloys were investigated. It is shown that precrystallization annealing of niobium-molybdenum, niobium-vanadium and niobium-zirconium alloys elevates much more sufficiently their resistance to microplastic strains, than to macroplastic strains. Hardening effect differs sufficiently for different alloys. The maximal hardening is observed for niobium-vanadium alloys, the minimal one - for niobium-zirconium alloys

Strength of precast concrete shear joints reinforced with high-strength wire ropes

DEFF Research Database (Denmark)

Joergensen, Henrik B.; Hoang, Linh Cao; Hagsten, Lars German

2017-01-01

This paper concerns the in-plane shear strength of connections between precast concrete wall elements reinforced with looped high-strength wire ropes. The looped wire ropes are pre-installed in so-called ‘wire boxes’ which function as shear keys. Although only a small amount of research...... on the shear strength of such connections can be found in the literature, this type of connection is increasingly being used because wire ropes are much more construction-friendly than traditional U-bars. A rigid plastic upper bound model for the shear strength of wall connections reinforced with looped wire...... ropes that are pre-installed in wire boxes is presented along with test results on the shear strength of connections with double-wire boxes. It is shown that the plastic solution agrees well with both the obtained test results and results from previously conducted tests....

Design of rapid hardening engineered cementitious composites for sustainable construction

Directory of Open Access Journals (Sweden)

Marushchak Uliana

2017-12-01

Full Text Available This paper deals with design of environmentally friendly Rapid Hardening Engineered Cementitious Composite (RHECC nanomodified with ultrafine mineral additives, polycarboxylate ether based superplasticizer, calcium hydrosilicate nanoparticles and dispersal reinforced by fibers. The incremental coefficient of surface activity was proposed in order to estimation of ultrafine supplementary materials (fly ash, methakaolin, microsilica efficiency. A characterization of RHECC’s compressive and flexural properties at different ages is reported in this paper. Early compressive strength of ECC is 45-50 MPa, standard strength – 84-95 MPa and parameter Rc2/Rc28 – 65–70%. The microstructure of the cement matrix and RHECC was investigated. The use of ultrafine mineral supplementary materials provides reinforcement of structure on micro- and nanoscale level (cementing matrix due to formation of sub-microreinforcing hydrate phase as AFt- and C-S-H phases in unclinker part of cement matrix, resulting in the phenomena of “self-reinforcement” on the microstructure level. Designed RHECC may be regarded as lower brittle since the crack resistance coefficient is higher comparison to conventional fine grain concrete.

Design of rapid hardening engineered cementitious composites for sustainable construction

Science.gov (United States)

Marushchak, Uliana; Sanytsky, Myroslav; Sydor, Nazar

2017-12-01

This paper deals with design of environmentally friendly Rapid Hardening Engineered Cementitious Composite (RHECC) nanomodified with ultrafine mineral additives, polycarboxylate ether based superplasticizer, calcium hydrosilicate nanoparticles and dispersal reinforced by fibers. The incremental coefficient of surface activity was proposed in order to estimation of ultrafine supplementary materials (fly ash, methakaolin, microsilica) efficiency. A characterization of RHECC's compressive and flexural properties at different ages is reported in this paper. Early compressive strength of ECC is 45-50 MPa, standard strength - 84-95 MPa and parameter Rc2/Rc28 - 65-70%. The microstructure of the cement matrix and RHECC was investigated. The use of ultrafine mineral supplementary materials provides reinforcement of structure on micro- and nanoscale level (cementing matrix) due to formation of sub-microreinforcing hydrate phase as AFt- and C-S-H phases in unclinker part of cement matrix, resulting in the phenomena of "self-reinforcement" on the microstructure level. Designed RHECC may be regarded as lower brittle since the crack resistance coefficient is higher comparison to conventional fine grain concrete.

Fresh and Hardened State of Polymer Modified Concrete and Mortars – A Review

Directory of Open Access Journals (Sweden)

Tukimat Nurul Nadrah Aqilah

2017-01-01

Full Text Available Polymer modified concrete or mortar is an alternative to the advancement of long serving civil engineering material - mortar and concrete. The excellence and promising benefits of modified composites have led to numerous progressive studies of its application. This paper presented a critical review from previous research on the polymer modified concrete and mortar. Both fresh and hardened state behaviours were reviewed as they are important for the development of excellent engineering material. Most of the applications of polymer modified concrete and mortar can be seen in diverse types of polymer such as latex, epoxy and emulsion. The utilization of each type of polymers resulted in different characteristics of composite concrete or mortar. Such applications have contributed to the improvement in terms of workability and mechanical strength, especially at higher grade of composite strength of concrete material.

Radiation-hardened micro-electronics for nuclear instrumentation

International Nuclear Information System (INIS)

Van Uffelen, M.

2007-01-01

The successful development and deployment of future fission and thermonuclear fusion reactors depends to a large extent on the advances of different enabling technologies. Not only the materials need to be custom engineered but also the instrumentation, the electronics and the communication equipment need to support operation in this harsh environment, with expected radiation levels during maintenance up to several MGy. Indeed, there are yet no commercially available electronic devices available off-the-shelf which demonstrated a satisfying operation at these extremely high radiation levels. The main goal of this task is to identify commercially available radiation tolerant technologies, and to design dedicated and integrated electronic circuits, using radiation hardening techniques, both at the topological and architectural level. Within a stepwise approach, we first design circuits with discrete components and look for an equivalent integrated technology. This will enable us to develop innovative instrumentation and communication tools for the next generation of nuclear reactors, where both radiation hardening and miniaturization play a dominant role

Evaluation of critical resolved shear strength and deformation mode in proton-irradiated austenitic stainless steel using micro-compression tests

Energy Technology Data Exchange (ETDEWEB)

Jin, Hyung-Ha; Ko, Eunsol; Kwon, Junhyun; Hwang, Seong Sik [Nuclear Materials Safety Research Division, Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon, 305-353 (Korea, Republic of); Shin, Chansun, E-mail: c.shin@mju.ac.kr [Department of Materials Science and Engineering, Myongji University, 116 Myongji-ro, Cheoin-gu, Youngin, Gyeonggi-do, 449-728 (Korea, Republic of)

2016-03-15

Micro-compression tests were applied to evaluate the changes in the strength and deformation mode of proton-irradiated commercial austenitic stainless steel. Proton irradiation generated small dots at low dose levels and Frank loops at high dose levels. The increase in critical resolved shear stresses (CRSS) was measured from micro-compression of pillars and the Schmid factor calculated from the measured loading direction. The magnitudes of the CRSS increase were in good agreement with the values calculated from the barrier hardening model using the measured size and density of radiation defects. The deformation mode changed upon increasing the irradiation dose level. At a low radiation dose level, work hardening and smooth flow behavior were observed. Increasing the dose level resulted in the flow behavior changing to a distinct heterogeneous flow, yielding a few large strain bursts in the stress–strain curves. The change in the deformation mode was related to the formation and propagation of defect-free slip bands. The effect of the orientation of the pillar or loading direction on the strengths is discussed.

Three-Sheet Spot Welding of Advanced High-Strength Steels

DEFF Research Database (Denmark)

Nielsen, Chris Valentin; Friis, Kasper Storgaard; Zhang, W.

2011-01-01

The automotive industry has introduced the three-layer weld configuration, which represents new challenges compared to normal two-sheet lap welds. The process is further complicated by introducing high-strength steels in the joint. The present article investigates the weldability of thin, low....... The weld mechanisms are analyzed numerically and compared with metallographic analyses showing how the primary bonding mechanism between the thin, low-carbon steel sheet and the thicker sheet of high-strength steel is solid-state bonding, whereas the two high-strength steels are joined by melting, forming...... a weld nugget at their mutual interface. Despite the absence of the typical fusion nugget through the interface between the low-carbon steel and high-strength steel, the weld strengths obtained are acceptable. The failure mechanism in destructive testing is ductile fracture with plug failure....

The maraging steel corrosion properties with hardening of different kinds after double aging

Directory of Open Access Journals (Sweden)

L. V. Tarasenko

2014-01-01

Full Text Available The paper proposes to use high-strength corrosion-resistant maraging steels, which were developed for aircraft industry instead of carbon steel with coating to improve operation properties of the forcemeasuring resilient member in electronic strain-gauge balance.It examines the possibility to apply the martensitic-aging steels of Fe-Cr-Ni-Mo-Ti (ЭП678 and Fe-Cr-Ni-Mo-Cu-Nb (ЭП817 alloying systems. It was shown, that a traditional heat strain-hardening treatment including hardening and overageing of this steels provides combination of durability viscosity and corrosion- resistance, but at the same time it increases nonelastic effects and lowers the limit of elasticity because of reversing austenite formation. In this connection, it was proposed to use hardening with double aging i.e. main and low-temperature aging with no austenite formation as heat strainhardening treatment of steels for force-measuring resilient member. The goal of this work was to study the influence of double aging on the structure and properties of ЭП678 (06Х14Н6Д2МБТ and ЭП817 (03Х111Н10М2Т steels.The modes of double aging for ЭП817 steel were conformed to 4500С + 400 0С and 475 0С+ 400 0С, for ЭП678 steel – 530 0С + 500 0С. The structure and properties of hardened steels after main and double aging were compared.Metallographic analysis of samples after electrolytic etching was conducted with Leitz Metallovert microscope while the CamScan 4DV raster electronic microscope was used for Microroentgen-spectral analysis. The quantity of austenite was controlled with computerized setting DRON-4, the hardness was measured with ТК-2М instrument, corrosion-resistance was estimated with polarized curves, which were taken using a П-5848 potentiostat.The conducted research has shown, that double aging causes the additional hardening of steels due to disintegration of martensite and formation of dispersed Cu – corpuscles in ЭП817 steel and of Ni3Ti

Experience of high-nitrogenous steel powder application in repairs and surface hardening of responsible parts for power equipment by plasma spraying

Science.gov (United States)

Kolpakov, A. S.; Kardonina, N. I.

2016-02-01

The questions of the application of novel diffusion-alloying high-nitrogenous steel powders for repair and surface hardening of responsible parts of power equipment by plasma spraying are considered. The appropriateness of the method for operative repair of equipment and increasing its service life is justified. General data on the structure, properties, and manufacture of nitrogen-, aluminum-, and chromium-containing steel powders that are economically alloyed using diffusion are described. It is noted that the nitrogen release during the decomposition of iron nitrides, when heating, protects the powder particles from oxidation in the plasma jet. It is shown that the coating retains 50% of nitrogen that is contained in the powder. Plasma spraying modes for diffusion-alloying high-nitrogenous steel powders are given. The service properties of plasma coatings based on these powders are analyzed. It is shown that the high-nitrogenous steel powders to a nitrogen content of 8.9 wt % provide the necessary wear resistance and hardness of the coating and the strength of its adhesion to the substrate and corrosion resistance to typical aggressive media. It is noted that increasing the coating porosity promotes stress relaxation and increases its thickness being limited with respect to delamination conditions in comparison with dense coatings on retention of the low defectiveness of the interface and high adhesion to the substrate. The examples of the application of high-nitrogenous steel powders in power engineering during equipment repairs by service companies and overhaul subdivisions of heat power plants are given. It is noted that the plasma spraying of diffusion-alloyed high-nitrogenous steel powders is a unique opportunity to restore nitrided steel products.

Effects of welding and post-weld heat treatments on nanoscale precipitation and mechanical properties of an ultra-high strength steel hardened by NiAl and Cu nanoparticles

International Nuclear Information System (INIS)

Jiao, Z.B.; Luan, J.H.; Guo, W.; Poplawsky, J.D.; Liu, C.T.

2016-01-01

The effects of welding and post-weld heat treatment (PWHT) on nanoscale co-precipitation, grain structure, and mechanical properties of an ultra-high strength steel were studied through a combination of atom probe tomography (APT) and mechanical tests. Our results indicate that the welding process dissolves all pre-existing nanoparticles and causes grain coarsening in the fusion zone, resulting in a soft and ductile weld without any cracks in the as-welded condition. A 550 °C PWHT induces fine-scale re-precipitation of NiAl and Cu co-precipitates with high number densities and ultra-fine sizes, leading to a large recovery of strength but a loss of ductility with intergranular failure, whereas a 600 °C PWHT gives rise to coarse-scale re-precipitation of nanoparticles together with the formation of a small amount of reverted austenite, resulting in a great recovery in both strength and ductility. Our analysis indicates that the degree of strength recovery is dependent mainly upon the re-precipitation microstructure of nanoparticles, together with grain size and reversion of austenite, while the ductility recovery is sensitive to the grain-boundary structure. APT reveals that the grain-boundary segregation of Mn and P may be the main reason for the 550 °C embrittlement, and the enhanced ductility at 600 °C is ascribed to a possible reduction of the segregation and reversion of austenite.

Investigation of srawberry hardening in low temperatures in vitro

OpenAIRE

Lukoševičiūtė, Vanda; Rugienius, Rytis; Kavaliauskaitė, Danguolė

2007-01-01

Cold resistance of different strawberry varieties in vitro and ability to retain hardening after defrosting and repeated hardening. Phytohormons – gibberellin and abscisic acid added in the growing medium were investigated in Horticulture plant genetic and biotechnology department of LIH. We tried to model common conditions in temperate zone when freeze-thaw cycles often occur during wintertime. For investigation in vitro strawberries for the first time hardened in light at the temperature of...

High-strength mineralized collagen artificial bone

Science.gov (United States)

Qiu, Zhi-Ye; Tao, Chun-Sheng; Cui, Helen; Wang, Chang-Ming; Cui, Fu-Zhai

2014-03-01

Mineralized collagen (MC) is a biomimetic material that mimics natural bone matrix in terms of both chemical composition and microstructure. The biomimetic MC possesses good biocompatibility and osteogenic activity, and is capable of guiding bone regeneration as being used for bone defect repair. However, mechanical strength of existing MC artificial bone is too low to provide effective support at human load-bearing sites, so it can only be used for the repair at non-load-bearing sites, such as bone defect filling, bone graft augmentation, and so on. In the present study, a high strength MC artificial bone material was developed by using collagen as the template for the biomimetic mineralization of the calcium phosphate, and then followed by a cold compression molding process with a certain pressure. The appearance and density of the dense MC were similar to those of natural cortical bone, and the phase composition was in conformity with that of animal's cortical bone demonstrated by XRD. Mechanical properties were tested and results showed that the compressive strength was comparable to human cortical bone, while the compressive modulus was as low as human cancellous bone. Such high strength was able to provide effective mechanical support for bone defect repair at human load-bearing sites, and the low compressive modulus can help avoid stress shielding in the application of bone regeneration. Both in vitro cell experiments and in vivo implantation assay demonstrated good biocompatibility of the material, and in vivo stability evaluation indicated that this high-strength MC artificial bone could provide long-term effective mechanical support at human load-bearing sites.

Work Hardening Behavior of 1020 Steel During Cold-Beating Simulation

Science.gov (United States)

CUI, Fengkui; LING, Yuanfei; XUE, Jinxue; LIU, Jia; LIU, Yuhui; LI, Yan

2017-03-01

The present research of cold-beating formation mainly focused on roller design and manufacture, kinematics, constitutive relation, metal flow law, thermo-mechanical coupling, surface micro-topography and microstructure evolution. However, the research on surface quality and performance of workpieces in the process of cold-beating is rare. Cold-beating simulation experiment of 1020 steel is conducted at room temperature and strain rates ranging from 2000 to 4000 s-1 base on the law of plastic forming. According to the experimental data, the model of strain hardening of 1020 steel is established, Scanning Electron Microscopy(SEM) is conducted, the mechanism of the work hardening of 1020 steel is clarified by analyzing microstructure variation of 1020 steel. It is found that the strain rate hardening effect of 1020 steel is stronger than the softening effect induced by increasing temperatures, the process of simulation cold-beating cause the grain shape of 1020 steel significant change and microstructure elongate significantly to form a fibrous tissue parallel to the direction of deformation, the higher strain rate, the more obvious grain refinement and the more hardening effect. Additionally, the change law of the work hardening rate is investigated, the relationship between dislocation density and strain, the relationship between work hardening rate and dislocation density is obtained. Results show that the change trend of the work hardening rate of 1020 steel is divided into two stages, the work hardening rate decreases dramatically in the first stage and slowly decreases in the second stage, finally tending toward zero. Dislocation density increases with increasing strain and strain rate, work hardening rate decreases with increasing dislocation density. The research results provide the basis for solving the problem of improving the surface quality and performance of workpieces under cold-beating formation of 1020 steel.

A procedure for the hardening of materials

International Nuclear Information System (INIS)

Dearnaley, G.

1984-01-01

A method of hardening metals or ceramics which have fcc, bcc or hcp structures in which two species of differing atomic radii are introduced into the material to be hardened. One species is of a size such that it can diffuse through the lattice normally. The other is of a size such that it can diffuse readily only along dislocations. Ion bombardment is the preferred method of introducing the species with different atomic radii. The material to be hardened is subjected to heat and plastic deformation so as to cause a large number of dislocations with jogs. The species meet at the jogs where they interact and are trapped and set up strain fields which prevent further deformation of the material. (author)

The mechanical properties and microstructures of vanadium bearing high strength dual phase steels processed with continuous galvanizing line simulations

Science.gov (United States)

Gong, Yu

For galvanized or galvannealed steels to be commercially successful, they must exhibit several attributes: (i) easy and inexpensive processing in the hot mill, cold mill and on the coating line, (ii) high strength with good formability and spot weldability, and (iii) good corrosion resistance. At the beginning of this thesis, compositions with a common base but containing various additions of V or Nb with or without high N were designed and subjected to Gleeble simulations of different galvanizing(GI), galvannealing(GA) and supercooling processing. The results revealed the phase balance was strongly influenced by the different microalloying additions, while the strengths of each phase were somewhat less affected. Our research revealed that the amount of austenite formed during intercritical annealing can be strongly influenced by the annealing temperature and the pre-annealing conditions of the hot band (coiling temperature) and cold band (% cold reduction). In the late part of this thesis, the base composition was a low carbon steel which would exhibit good spot weldability. To this steel were added two levels of Cr and Mo for strengthening the ferrite and increasing the hardenability of intercritically formed austenite. Also, these steels were produced with and without the addition of vanadium in an effort to further increase the strength. Since earlier studies revealed a relationship between the nature of the starting cold rolled microstructure and the response to CGL processing, the variables of hot band coiling temperature and level of cold reduction prior to annealing were also studied. Finally, in an effort to increase strength and ductility of both the final sheet (general formability) and the sheared edges of cold punched holes (local formability), a new thermal path was developed that replaced the conventional GI ferrite-martensite microstructure with a new ferrite-martensite-tempered martensite and retained austenite microstructure. The new

Low-cycle fatigue behaviors of pre-hardening Hadfield steel

Energy Technology Data Exchange (ETDEWEB)

Chen, Chen [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Lv, Bo [College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Wang, Fei [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Zhang, Fucheng, E-mail: zfc@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004 (China)

2017-05-17

Low-cycle fatigue behaviors of the pre-hardening (PH) and the water-quenching (WQ) Hadfield steel were studied using optical microscopy, transmission electron microscopy, and electron backscatter diffraction technique. The effect of the PH treatment on low-cycle fatigue behavior of the Hadfield steel was analyzed through comparing the cyclic hardening/softening behaviors and the changing regulations of stress amplitude, internal stress, and effective stress at different total strain amplitudes. Results showed obvious differences in fatigue behaviors between the PH (with a cold rolling deformation degree of 40%) and the WQ Hadfield steels. Transient hardening followed by cyclic stability behavior occurred in the PH Hadfield steel under cyclic loading, whereas cyclic softening behavior was barely observed. The fatigue life of the PH Hadfield steel was higher than that of the WQ Hadfield steel at relatively low strain amplitudes, while a contrary result was obtained at relatively high strain amplitudes. At low strain amplitudes, the deformation twins induced in the PH Hadfield steel could enhance the multiplication and slip process of dislocations, which actually improved the deformation uniformity. The long-range motion of dislocations was intensified at high strain amplitudes. However, the dislocation motion was also blocked by twin boundaries. As a result, the interactions between dislocations and deformation twins enhanced, finally causing severe dislocation accumulation. These two effects of deformation twins on dislocation motion eventually resulted in different low-cycle fatigue behaviors of the PH Hadfield steel.

Investigation of secondary hardening in Co–35Ni–20Cr–10Mo alloy using analytical scanning transmission electron microscopy

International Nuclear Information System (INIS)

Sorensen, D.; Li, B.Q.; Gerberich, W.W.; Mkhoyan, K.A.

2014-01-01

The mechanism of secondary hardening in MP35N (Co–35Ni–20Cr–10Mo) alloy due to exposures at elevated temperatures has been studied. It was observed that short exposure to elevated temperatures increased the ultimate tensile strength and yield stress while decreasing the elongation of MP35N wires. Upon aging at temperatures from 300 to 900 °C the elastic modulus increased although no changes in crystallographic orientation or microstructure were observed. The grain size and major texture components were unchanged following aging. Analytical scanning transmission electron microscope investigation showed that MP35N is hardened by preferential segregation of molybdenum to stacking faults and deformation twins. It also revealed that the concentration of molybdenum segregation was proportional to the amount of initial cold work before aging

ANISOTROPIC STRAIN-HARDENING IN POLYCRYSTALLINE COPPER AND ALUMINUM

NARCIS (Netherlands)

HESS, F

1993-01-01

A new viscoplastic model for the plastic stress-strain behaviour of f.c.c. metals is presented. In this model the strain hardening results from increasing dislocation densities. The observed stagnation of strain hardening after strain reversals is explained by a lowering of the increase in

Surface hardening of titanium alloys with melting depth controlled by heat sink

Science.gov (United States)

Oden, Laurance L.; Turner, Paul C.

1995-01-01

A process for forming a hard surface coating on titanium alloys includes providing a piece of material containing titanium having at least a portion of one surface to be hardened. The piece having a portion of a surface to be hardened is contacted on the backside by a suitable heat sink such that the melting depth of said surface to be hardened may be controlled. A hardening material is then deposited as a slurry. Alternate methods of deposition include flame, arc, or plasma spraying, electrodeposition, vapor deposition, or any other deposition method known by those skilled in the art. The surface to be hardened is then selectively melted to the desired depth, dependent on the desired coating thickness, such that a molten pool is formed of the piece surface and the deposited hardening material. Upon cooling a hardened surface is formed.

Laser Cladding of CPM Tool Steels on Hardened H13 Hot-Work Steel for Low-Cost High-Performance Automotive Tooling

Science.gov (United States)

Chen, J.; Xue, L.

2012-06-01

This paper summarizes our research on laser cladding of high-vanadium CPM® tool steels (3V, 9V, and 15V) onto the surfaces of low-cost hardened H13 hot-work tool steel to substantially enhance resistance against abrasive wear. The results provide great potential for fabricating high-performance automotive tooling (including molds and dies) at affordable cost. The microstructure and hardness development of the laser-clad tool steels so obtained are presented as well.

On the hardenability of Nb-modified metastable beta Ti-5553 alloy

Energy Technology Data Exchange (ETDEWEB)

Campo, K.N.; Andrade, D.R.; Opini, V.C.; Mello, M.G.; Lopes, E.S.N.; Caram, R., E-mail: caram@fem.unicamp.br

2016-05-15

Among the commercially available titanium alloys, the metastable β Ti-5553 alloy (Ti–5Al–5V–5Mo–3Cr–0.5Fe wt.%) is an object of great interest because it is employed in aerospace structural applications, primarily in the replacement of steel components. One of the primary advantages of this alloy is its high hardenability, which allows it to retain the β phase at room temperature, even at low cooling rates, thereby allowing the thermoprocessing of thick parts. The aim of this investigation was to evaluate the effect of the replacement of V with Nb on the hardenability of Ti-5553. Based on the molybdenum equivalent criterion, the Nb-modified Ti-5553 alloy was designed to present 12 wt.% of Nb instead of 5 wt.% of V. Samples of both alloys were prepared by melting them in an arc furnace under an inert atmosphere, heat-treated at high temperatures for 12 h and plastic deformed using swage forging. Finally, these samples were solution heat-treated at temperatures above the β-transus followed by cooling at different rates using water quenching, furnace cooling and a modified Jominy end quench test. Characterization was performed by measuring Vickers hardness, X-ray diffraction, and light optical, scanning electron and transmission electron microscopy. The results obtained indicate that metastable β phase can be retained when the cooling rate is higher than 21 °C/s for both alloys. At lower cooling rates, α phase precipitation was observed, but it appeared to be less evident in the Nb-modified Ti-5553, suggesting that the replacement of V with Nb increased the hardenability of the alloy. - Highlights: • Hardenability of Ti alloys are assessed using a modified Jominy end quench test. • Ti-5553 and Nb-modified Ti-5553 are subjected to continuous cooling experiments. • β phase decomposition kinetics is reduced by replacing V with Nb in Ti-5553. • Nb-modified Ti-5553 features improved hardenability. • Replacement of V with Nb causes the �

The influence of stacking fault energy on the mechanical behavior of Cu and Cu-Al alloys: Deformation twinning, work hardening, and dynamic recovery

Science.gov (United States)

Rohatgi, Aashish; Vecchio, Kenneth S.; Gray, George T.

2001-01-01

The role of stacking fault energy (SFE) in deformation twinning and work hardening was systematically studied in Cu (SFE ˜78 ergs/cm2) and a series of Cu-Al solid-solution alloys (0.2, 2, 4, and 6 wt pct Al with SFE ˜75, 25, 13, and 6 ergs/cm2, respectively). The materials were deformed under quasi-static compression and at strain rates of ˜1000/s in a Split-Hopkinson pressure bar (SHPB). The quasi-static flow curves of annealed 0.2 and 2 wt pct Al alloys were found to be representative of solid-solution strengthening and well described by the Hall-Petch relation. The quasi-static flow curves of annealed 4 and 6 wt pct Al alloys showed additional strengthening at strains greater than 0.10. This additional strengthening was attributed to deformation twins and the presence of twins was confirmed by optical microscopy. The strengthening contribution of deformation twins was incorporated in a modified Hall-Petch equation (using intertwin spacing as the “effective” grain size), and the calculated strength was in agreement with the observed quasi-static flow stresses. While the work-hardening rate of the low SFE Cu-Al alloys was found to be independent of the strain rate, the work-hardening rate of Cu and the high SFE Cu-Al alloys (low Al content) increased with increasing strain rate. The different trends in the dependence of work-hardening rate on strain rate was attributed to the difference in the ease of cross-slip (and, hence, the ease of dynamic recovery) in Cu and Cu-Al alloys.

Research on SEU hardening of heterogeneous Dual-Core SoC

Science.gov (United States)

Huang, Kun; Hu, Keliu; Deng, Jun; Zhang, Tao

2017-08-01

The implementation of Single-Event Upsets (SEU) hardening has various schemes. However, some of them require a lot of human, material and financial resources. This paper proposes an easy scheme on SEU hardening for Heterogeneous Dual-core SoC (HD SoC) which contains three techniques. First, the automatic Triple Modular Redundancy (TMR) technique is adopted to harden the register heaps of the processor and the instruction-fetching module. Second, Hamming codes are used to harden the random access memory (RAM). Last, a software signature technique is applied to check the programs which are running on CPU. The scheme need not to consume additional resources, and has little influence on the performance of CPU. These technologies are very mature, easy to implement and needs low cost. According to the simulation result, the scheme can satisfy the basic demand of SEU-hardening.

The effect of gas tungsten arc welding and pulsed-gas tungsten arc welding processes’ parameters on the heat affected zone-softening behavior of strain-hardened Al–6.7Mg alloy

International Nuclear Information System (INIS)

Hadadzadeh, Amir; Ghaznavi, Majid Mahmoudi; Kokabi, Amir Hossein

2014-01-01

Highlights: • The strain-hardened Al–6.7Mg alloy was welded using GTAW and PGTAW processes. • The HAZ softening behavior of the welding joint was characterized. • Employing pulsed current in GTAW process eliminated the HAZ softening. • Duration ratio did not affect the weld strength while the frequency influenced it. - Abstract: The heat affected zone (HAZ) softening behavior of strain-hardened Al–6.7Mg alloy welded by gas tungsten arc welding (GTAW) process was investigated. Increasing the heat input during welding led to formation of a wider HAZ. Moreover, the size of the precipitates was increased at higher heat inputs. Consequently, by increasing the heat input, lower strength was obtained for the welding joints. At the second stage of the study, pulsed-GTAW (PGTAW) process was employed to improve the strength of the joints. It was observed that the overall strength of the welding joints was improved and the fracture during tensile test was moved from the HAZ to the fusion zone. Moreover, the effect of duration ratio and pulse frequency was studied. For the current study, the duration ratio did not have a significant effect on the strength and microstructure of the weld, but increasing the frequency led to higher strength of the weld and finer microstructure

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.)

Hardening and softening mechanisms of pearlitic steel wire under torsion

International Nuclear Information System (INIS)

Zhao, Tian-Zhang; Zhang, Shi-Hong; Zhang, Guang-Liang; Song, Hong-Wu; Cheng, Ming

2014-01-01

Highlights: • Mechanical behavior of pearlitic steel wire is studied using torsion. • Work hardening results from refinement lamellar pearlitic structure. • Softening results from recovery, shear bands and lamellar fragmentations. • A microstructure based analytical flow stress model is established. - Abstract: The mechanical behaviors and microstructure evolution of pearlitic steel wires under monotonic shear deformation have been investigated by a torsion test and a number of electron microscopy techniques including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), with an aim to reveal the softening and hardening mechanisms of a randomly oriented pearlitic structure during a monotonic stain path. Significantly different from the remarkable strain hardening in cold wire drawing, the strain hardening rate during torsion drops to zero quickly after a short hardening stage. The microstructure observations indicate that the inter-lamellar spacing (ILS) decreases and the dislocations accumulate with strain, which leads to hardening of the material. Meanwhile, when the strain is larger than 0.154, the enhancement of dynamic recovery, shear bands (SBs) and cementite fragmentations results in the softening and balances the strain hardening. A microstructure based analytical flow stress model with considering the influence of ILS on the mean free path of dislocations and the softening caused by SBs and cementite fragmentations, has been established and the predicted flow shear curve meets well with the measured curve in the torsion test

Cellular Composites with Ambient and Autoclaved Type of Hardening with Application of Nanostructured Binder

International Nuclear Information System (INIS)

Nelyubova, V; Pavlenko, N; Netsvet, D

2015-01-01

The research presents the dimensional and structural characteristics of nonhydrational hardening binders - nanostructured binders. Rational areas of their use in composites for construction purposes are given. The paper presents the results of the development of natural hardening foam concrete and aerated autoclaved concrete for thermal insulating and construction and thermal insulating purposes. Thus nanostructured binder (NB) in the composites was used as a primary binder and a high reactive modifier. (paper)

Design Features of Hardening Turners with Outstripping Plastic Deformation

Directory of Open Access Journals (Sweden)

V. M. Yaroslavtsev

2014-01-01

accuracy of a device to exclude unexpected displacements of hardener with respect to the surface of cutting.The article also gives main recommendations to choose design parameters of the crush rolls for OPD.Taking into consideration the above production requirements and recommendations to design the turning devices with OPD allows us to create technological equipment to provide high efficiency of a method. The equipment is convenient for work, simple and cheap in the production, available for repair and replacement of worn-out constructive components, and safe in operation as well.

Green and early age compressive strength of extruded cement mortar monitored with compression tests and ultrasonic techniques

International Nuclear Information System (INIS)

Voigt, Thomas; Malonn, Tim; Shah, Surendra P.

2006-01-01

Knowledge about the early age compressive strength development of cementitious materials is an important factor for the progress and safety of many construction projects. This paper uses cylindrical mortar specimens produced with a ram extruder to investigate the transition of the mortar from plastic and deformable to hardened state. In addition, wave transmission and reflection measurements with P- and S-waves were conducted to obtain further information about the microstructural changes during the setting and hardening process. The experiments have shown that uniaxial compression tests conducted on extruded mortar cylinders are a useful tool to evaluate the green strength as well as the initiation and further development of the compressive strength of the tested material. The propagation of P-waves was found to be indicative of the internal structure of the tested mortars as influenced, for example, by the addition of fine clay particles. S-waves used in transmission and reflection mode proved to be sensitive to the inter-particle bonding caused by the cement hydration and expressed by an increase in compressive strength

Mechanical properties of high-strength concrete

Science.gov (United States)

Mokhtarzadeh, Alireza

This report summarizes an experimental program conducted to investigate production techniques and mechanical properties of high strength concrete in general and to provide recommendations for using these concretes in manufacturing precast/prestressed bridge girders. Test variables included total amount and composition of cementitious material (portland cement, fly ash, and silica fume), type and brand of cement, type of silica fume (dry densified and slurry), type and brand of high-range water-reducing admixture, type of aggregate, aggregate gradation, maximum aggregate size, and curing. Tests were conducted to determine the effects of these variables on changes in compressive strength and modulus of elasticity over time, splitting tensile strength, modulus of rupture, creep, shrinkage, and absorption potential (as an indirect indicator of permeability). Also investigated were the effects of test parameters such as mold size, mold material, and end condition. Over 6,300 specimens were cast from approximately 140 mixes over a period of 3 years.

Applicability of Voce equation for tensile flow and work hardening behaviour of P92 ferritic steel

International Nuclear Information System (INIS)

Sainath, G.; Choudhary, B.K.; Christopher, J.; Isaac Samuel, E.; Mathew, M.D.

2015-01-01

Detailed analysis of true stress (σ)-true plastic strain (ε) data indicated that tensile flow behaviour of P92 ferritic steel can be adequately described by Voce equation at strain rates ranging from 3.16 × 10 −5 to 1.26 × 10 −3  s −1 over a temperature range 300–923 K. The steel exhibited two-stage work hardening in the variations of instantaneous work hardening rate (θ = dσ/dε) with stress. At all the strain rates, the variations in σ-ε, θ-σ and work hardening parameters associated with Voce equation with temperature exhibited three distinct temperature regimes. At intermediate temperatures, the variations in σ-ε, θ-σ and work hardening parameters with temperature and strain rate exhibited anomalous behaviour due to the occurrence of dynamic strain ageing in the steel. The shift in θ-σ towards low stresses, and rapid decrease in flow stress and work hardening parameters with increasing temperature and decreasing strain rate suggested dominance of dynamic recovery at high temperatures. - Highlights: • Tensile flow and work hardening behaviour of P92 steel has been examined. • Applicability of Voce equation to P92 steel is demonstrated. • Three temperature regimes in flow and work hardening has been observed. • Good match between predicted and the experimental tensile properties has been shown

Effect of rolling temperature on 12Kh18N10T steel tube hardening

International Nuclear Information System (INIS)

Yushkevich, P.M.; Stepanovich, V.E.; Manankova, L.V.; Usenko, V.N.; Semenov, I.A.

1984-01-01

Mechanical properties and substructure of tubes at the constant reduction degree k(the ratio of deformation over wall thickness to deformation over diameter), depending on strain degree during cold and hot tube rolling, have been studied. The investigations are carried out using hot-rolled tubes with the dimensions 88x8 mm of 12Kh1hN10T steel. With the decrease of strain over the wall of the tube, produced of 12Kh18N10T steel as to strain over diameter the values of yield strength and ultimate strength increase with simultaneous decrease in ductility during warm rolling and yield strength and ultimate strength decrease with the increase in ductility-during cold rolling. During warm rolling of the tubes at 250 deg C the hardening of 12Kh18N10T steel is higher, than at the rolling temperature 150 deg C. The optimum temperature range of warm rolling is 120-150 deg C. Grain orientation in the metal of the tubes and degree of texture perfection increase with the temperature increase of the tube warm drolling as compared with col rolli

Effects of thermomechanical processing on microstructure and properties of bainitic work hardening steel

Energy Technology Data Exchange (ETDEWEB)

Cao, Jie, E-mail: caojie910@ahut.edu.cn [School of Metallurgical Engineering, Anhui University of Technology, Ma’anshan 243002 (China); Yan, Jun; Zhang, Jing [School of Metallurgical Engineering, Anhui University of Technology, Ma’anshan 243002 (China); Yu, Tongren [Technology Center, Maanshan Iron & Steel Company Limited, Ma’anshan 243000 (China)

2015-07-15

The thermomechanical processing (TMP) of a bainitic work hardening steel was carried out on a Gleeble3500 simulator. The microstructure of processed specimens was investigated by means of optical and electron microscopy, and tensile tests were performed in a ZwickRoell tensile tester. The deformation temperatures of austenite varied from 800 °C to 900 °C. The cooling methods include single rate cooling method and two-stage cooling method. The two-stage cooling method includes fast cooling rates ranging from 4 °C/s to 12 °C/s and slow cooling rates ranging from 1 °C/s to 2 °C/s. It is shown that, within the range of parameters tested, the obtained microstructures are granular bainite, the tensile strength of the steel can be adjusted from 897.8 MPa to 1083.2 MPa, and good plasticity can be obtained at different strength levels.

Potential fatigue strength improvement of AA 5083-H111 notched parts by wire brush hammering: Experimental analysis and numerical simulation

International Nuclear Information System (INIS)

Sidhom, Naziha; Moussa, Naoufel Ben; Janeb, Sameh; Braham, Chedly; Sidhom, Habib

2014-01-01

Highlights: • Wire brush hammering increases by 20% the AA 5083-H111 notched parts fatigue limit. • Improvement of fatigue strength is related to the fatigue cracks nucleation. • Fatigue strength prediction accounts for wire brush hammering effects. - Abstract: The effects of milling as machining process and a post-machining treatment by wire-brush hammering, on the near surface layer characteristics of AA 5083-H111 were investigated. Surface texture, work-hardening and residual stress profiles were determined by roughness measurement, scanning electron microscope (SEM) examinations, microhardness and X-ray diffraction (XRD) measurements. The effects of surface preparation on the fatigue strength were assessed by bending fatigue tests performed on notched samples for two loading stress ratios R 0.1 and R 0.5 . It is found that the bending fatigue limit at R 0.1 and 10 7 cycles is 20% increased, with respect to the machined surface, by wire-brush hammering. This improvement was discussed on the basis of the role of surface topography, stabilized residual stress and work-hardening on the fatigue-crack network nucleation and growth. The effects biaxial residual stress field and surface work-hardening were taken into account in the finite element model. A multi-axial fatigue criterion was proposed to predict the fatigue strength of aluminum alloy notched parts for both machined and treated states

High strength Al–Al2O3p composites: Optimization of extrusion parameters

DEFF Research Database (Denmark)

Luan, B.F.; Hansen, Niels; Godfrey, A.

2011-01-01

Composite aluminium alloys reinforced with Al2O3p particles have been produced by squeeze casting followed by hot extrusion and a precipitation hardening treatment. Good mechanical properties can be achieved, and in this paper we describe an optimization of the key processing parameters...... on an investigation of their mechanical properties and microstructure, as well as on the surface quality of the extruded samples. The evaluation shows that material with good strength, though with limited ductility, can be reliably obtained using a production route of squeeze casting, followed by hot extrusion....... The parameters investigated are the extrusion temperature, the extrusion rate and the extrusion ratio. The materials chosen are AA 2024 and AA 6061, each reinforced with 30vol.% Al2O3 particles of diameter typically in the range from 0.15 to 0.3μm. The extruded composites have been evaluated based...

EN AW-4032 T6 Piston Alloy After High-Temperature Exposure: Residual Strength and Microstructural Features

Science.gov (United States)

Balducci, Eleonora; Ceschini, Lorella; Morri, Alessandro; Morri, Andrea

2017-08-01

This study aims to evaluate the effects of prolonged thermal exposure on both microstructural evolution and mechanical properties of the EN AW-4032 T6 piston alloy. For the purpose, the experimental activities have been carried out on samples machined from forged and heat-treated automotive pistons. The effects of overaging have been investigated in the temperature range of 140-290 °C, firstly by evaluating the time-temperature-hardness curves and then by carrying out room-temperature tensile tests on overaged samples. The material softening was substantial and extremely rapid when the soaking temperature exceeded 250 °C. During overaging, both the tensile strength and the residual hardness considerably decreased, and a relationship between these parameters has been established. The alloy behavior in the plastic field has been modeled according to the Hollomon's equation, showing that both the strain hardening exponent and the strength coefficient are a function of the residual hardness. The results were finally related to the corresponding microstructural changes: OM and FEG-SEM metallographic and fractographic analyses on overaged samples gave evidence of coarsened precipitates along the grain boundaries.

Radiation hardening of semiconductor parts

International Nuclear Information System (INIS)

Anon.

1993-01-01

This chapter is an overview of total-ionizing-dose and single-event hardening techniques and should be used as a guide to a range of research publications. It should be stressed that there is no clear and simple route to a radiation-tolerant silicon integrated circuit. What works for one fabrication process may not work for another, and there are many complex interactions within individual processes and designs. The authors have attempted to highlight the most important factors and those process changes which should bring improved hardness. The main point is that radiation-hardening as a procedure must be approached in a methodical fashion and with a good understanding of the response mechanisms involved

Microstructural origins of yield-strength changes in AISI 316 during fission or fusion irradiation

International Nuclear Information System (INIS)

Garner, F.A.; Hamilton, M.L.; Panayotou, N.F.; Johnson, G.D.

1981-08-01

The changes in yield strength of AISI 316 irradiated in breeder reactors have been successfully modeled in terms of concurrent changes in microstructural components. Two new insights involving the strength contributions of voids and Frank loops have been incorporated into the hardening models. Both the radiation-induced microstructure and the yield strength exhibit transients which are then followed by saturation at a level dependent on the irradiation temperature. Extrapolation to anticipated fusion behavior based on microstructural comparisons leads to the conclusion that the primary influence of transmutational differences is only to alter the transient behavior and not the saturation level of yield strength

Formability Characterization of a New Generation High Strength Steels

Energy Technology Data Exchange (ETDEWEB)

Sriram Sadagopan; Dennis Urban; Chris Wong; Mai Huang; Benda Yan

2003-05-16

Advanced high strength steels (AHSS) are being progressively explored by the automotive industry all around the world for cost-effective solutions to accomplish vehicle lightweighting, improve fuel economy, and consequently reduce greenhouse emissions. Because of their inherent high strength, attractive crash energy management properties, and good formability, the effective use of AHSS such as Duel Phase and TRIP (Transformation Induced Plasticity) steels, will significantly contribute to vehicle lightweighting and fuel economy. To further the application of these steels in automotive body and structural parts, a good knowledge and experience base must be developed regarding the press formability of these materials. This project provides data on relevant intrinsic mechanical behavior, splitting limits, and springback behavior of several lots of mild steel, conventional high strength steel (HSS), advanced high strength steel (AHSS) and ultra-high strength steel (UHSS), supplied by the member companies of the Automotive Applications Committee (AAC) of the American Iron and Steel Institute (AISI). Two lots of TRIP600, which were supplied by ThyssenKrupp Stahl, were also included in the study. Since sheet metal forming encompasses a very diverse range of forming processes and deformation modes, a number of simulative tests were used to characterize the forming behavior of these steel grades. In general, it was found that formability, as determined by the different tests, decreased with increased tensile strength. Consistant with previous findings, the formability of TRIP600 was found to be exceptionally good for its tensile strength.

Microstructure and age-hardening effects of aluminium alloys with additions of scandium and zirconium

Energy Technology Data Exchange (ETDEWEB)

Galun, R.; Mordike, B.L. [Inst. fuer Werkstoffkunde und Werkstofftechnik, Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany); Maiwald, T.; Smola, B. [Zentrum fuer Funktionswerkstoffe GmbH, Clausthal-Zellerfeld (Germany); Mergen, R.; Manner, M.; Uitz, W. [Miba Gleitlager GmbH, Laakirchen (Australia)

2004-12-01

The aim of the work presented in this report was to produce age-hardenable aluminium alloys containing scandium and zirconium by a casting process with similar cooling conditions like an industrial casting process. Microstructure, precipitation structure and age-hardening response of different alloys with up to 0.4 wt.% Sc and Zr were investigated. Age-hardening experiments from the as-cast condition without solution annealing showed a significant increase of hardness of about 100% for Sc-rich alloys and of 50% for Zr-rich alloys compared to the as-cast condition. TEM investigations revealed the formation of precipitates of ternary Al{sub 3}(Sc{sub x}Zr{sub 1-x}) phases with a cubic cP4 crystal structure. In addition to the strengthening effect, a high thermal stability especially of the precipitates in Zr-rich alloys up to 400 C let these alloys look very promising for high-temperature applications. (orig.)

Stress-relaxation tests in the work-hardening regime of tungsten single crystals below 300 K

International Nuclear Information System (INIS)

Brunner, D.

2008-01-01

The influence of work hardening on the results of stress-relaxation tests was studied for highly pure tungsten single crystals isothermally deformed at four temperatures of 274, 241, 131, and 78 K. A method accounting for strong work hardening on the determination of the strain-rate sensitivity from stress-relaxation tests is introduced by establishing special diagrams of SR tests denoted as YX diagrams

Nonlinear kinematic hardening under non-proportional loading

International Nuclear Information System (INIS)

Ottosen, N.S.

1979-07-01

Within the framework of conventional plasticity theory, it is first determined under which conditions Melan-Prager's and Ziegler's kinematic hardening rules result in identical material behaviour. Next, assuming initial isotropy and adopting the von Mises yield criterion, a nonlinear kinematic hardening function is proposed for prediction of metal behaviour. The model assumes that hardening at a specific stress point depends on the direction of the new incremental loading. Hereby a realistic response is obtained for general reversed loading, and a smooth behaviour is assured, even when loading deviates more and more from proportional loading and ultimately results in reversed loading. The predictions of the proposed model for non-proportional loading under plane stress conditions are compared with those of the classical linear kinematic model, the isotropic model and with published experimental data. Finally, the limitations of the proposaed model are discussed. (author)

Hardening cookies in web-based systems for better system integrity

International Nuclear Information System (INIS)

Mohamad Safuan Sulaiman; Mohd Dzul Aiman Aslan; Saaidi Ismail; Abdul Aziz Mohd Ramli; Abdul Muin Abdul Rahman; Siti Nurbahyah Hamdan; Norlelawati Hashimuddin; Sufian Norazam Mohamed Aris

2012-01-01

IT Center (ITC) as technical support and provider for most of web-based systems in Nuclear Malaysia has conducted a study to investigate cookie vulnerability in a system for better integrity. A part of the result has found that cookies in a web-based system in Nuclear Malaysia can be easily manipulated. The main objective of the study is to harden the vulnerability of the cookies. Two levels of security procedures have been used and enforced which consist of 1) Penetration test (Pen Test) 2) Hardening procedure. In one of the system, study has found that 121 attempts threats have been detected after the hardening enforcement from 23 March till 20 September 2012. At this stage, it can be concluded that cookie vulnerability in the system has been hardened and integrity has been assured after the enforcement. This paper describes in detail the penetration and hardening process of cookie vulnerability for better supporting web-based system in Nuclear Malaysia. (author)

On use of radial evanescence remain term in kinematic hardening

International Nuclear Information System (INIS)

Geyer, P.

1995-10-01

A fine modelling of the material' behaviour can be necessary to study the mechanical strength of nuclear power plant' components under cyclic loads. Ratchetting is one of the last phenomena for which numerical models have to be improved. We discuss in this paper on use of radial evanescence remain term in kinematic hardening to improve the description of ratchetting in biaxial loading tests. It's well known that Chaboche elastoplastic model with two non linear kinematic hardening variables initially proposed by Armstrong and Frederick, usually over-predicts accumulation of ratchetting strain. Burlet and Cailletaud proposed in 1987 a non linear kinematic rule with a radial evanescence remain term. The two models lead to identical formulation for proportional loadings. In the case of a biaxial loading test (primary+secondary loading), Burlet and Cailletaud model leads to accommodation, when Chaboche one's leads to ratchetting with a constant increment of strain. So we can have an under-estimate with the first model and an over-estimate with the second. An easy method to improve the description of ratchetting is to combine the two kinematic rules. Such an idea is already used by Delobelle in his model. With analytical results in the case of tension-torsion tests, we show in a first part of the paper, the interest of radial evanescence remain term in the non linear kinematic rule to describe ratchetting: we give the conditions to get adaptation, accommodation or ratchetting and the value of the strain increment in the last case. In the second part of the paper, we propose to modify the elastoplastic Chaboche model by coupling the two types of hardening by means of two scalar parameters which can be identified independently on biaxial loading tests. Identification of these two parameters returns to speculate on the directions of strain in order to adjust the ratchetting to experimental observations. We use the experimental results on the austenitic steel 316L at room

Changes of strength characteristics of pervious concrete due to variations in water to cement ratio

Science.gov (United States)

Kovac, M.; Sicakova, A.

2017-10-01

Pervious concrete is considered to be a sustainable pavement material due to high water permeability. The experiment presented in this paper was aimed at study the influence of water to cement ratio on both the compressive and splitting tensile strength of pervious concrete. Typically, less water content in concrete mixture leads to less porosity of cement paste and thus it provides desirable mechanical properties. In case of conventional dense concrete, the lower is the water to cement ratio, the higher or better is the strength, density and durability of concrete. This behaviour is not quite clear in case of pervious concrete because of low amount of cement paste present. Results of compressive and splitting tensile strength of pervious concrete are discussed in the paper while taking into account values measured after 2 and 28 days of hardening and variations in water to cement ratio. The results showed that changes of water to cement ratio from 0.25 to 0.35 caused only slight differences in strength characteristics, and this applied to both types of tested strength.

Stage IV work-hardening related to disorientations in dislocation structures

DEFF Research Database (Denmark)

Pantleon, W.

2004-01-01

The effect of deformation-induced disorientations on the work-hardening of metals is modelled based on dislocation dynamics. Essentially, Kocks’ dislocation model describing stage III hardening is extended to stage IV by incorporation of excess dislocations related to the disorientations....... Disorientations evolving from purely statistical reasons — leading to a square root dependence of the average disorientation angle on strain — affect the initial work-hardening rate (and the saturation stress) of stage III only slightly. On the other hand, deterministic contributions to the development...... of disorientations, as differences in the activated slip systems across boundaries, cause a linear increase of the flow stress at large strains. Such a constant work-hardening rate is characteristic for stage IV....

The effect of cobalt and molybdenum on the creep strength of low C-18Cr-10Ni steel

International Nuclear Information System (INIS)

Tomono, Yutaka; Ueda, Jitsuhiko

1982-01-01

The improvement of creep strength through the addition of cobalt and molybdenum to low C-18Cr-10Ni steel was studied at a temperature range of between 700 and 800 0 C. Changes in mechanical and physical properties such as lattice parameter and stacking fault energy, related to the additional elements were investigated to estimate the strengthening effect. Dislocation structures corresponding to the various creep stages were observed through a transmission electron microscope to distinguish the solution hardening effect of the added elements from the precipitation hardening effects of carbide. The results obtained are summarized as follows: (1) Addition of cobalt of up to 20% by weight improved the creep strength of austenitic steel. Addition of molybdenum of up to 5% by weight remarkably improved the creep strength of austenitic steel having a cobalt content of 20% by weight. (2) The trend for creep strength to improve with the addition of these elements was closely coincident with increases in lattice parameter and did not necessarily coincide with changes in the stacking fault energy. (author)

Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

Science.gov (United States)

Mohan, Nisha

Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

Fatigue strength of repaired cracks in welded connections made of very high strength steels

NARCIS (Netherlands)

Akyel, A.

2017-01-01

For cyclically loaded structures, fatigue design becomes one of the important design criteria. The state of art shows that with modification of the conventional structural design methodology, the use of very high strength steels may have a positive effect on fatigue strength of welded connections.

Evaluation of combined hardening parameters for type 304LN stainless steel under strain-controlled cyclic loading

International Nuclear Information System (INIS)

Kumar, Abhishek; Vishnuvardhan, S.; Raghava, G.

2016-01-01

Low cycle fatigue (LCF) is the primary degradation mechanism affecting coolant piping of pressurized water reactor (PWR) caused by combination of pressure and transient mechanical or thermal loads. In the case of LCF, stresses are high enough for plastic deformation to occur and the fatigue life is correlated with the cyclic plastic strain. Modelling cyclic plastic deformation of a material requires hardening parameters, which have to be obtained from LCF test results. It is customary in low cycle fatigue tests that the strain ranges are kept constant and the stresses are allowed to vary which typically leads to a hysteresis loop that consists of linear and nonlinear parts. In this paper, numerical studies on mechanical behaviour of Type 304LN stainless steel under fully reversed strain-controlled cyclic loading have been carried out. A linear combination of the two hardening types, isotropic and kinematic, governed by a scalar parameter, β (0 ≤β ≤ 1) is used. A value of β=1 indicates a pure isotropic hardening while a value of β=0 indicates pure kinematic hardening. The details of the combined isotropic-kinematic hardening model are also presented. Constitutive relations for the classical von Mises theory along with a bilinear hardening theory have been used. The model is implemented in finite element software ABAQUS using a user subroutine written in FORTRAN, UMAT. An iterative method is adopted to arrive at the model's hardening parameters and the value of β. (author)

Effect of aging hardening on in situ synthesis magnesium matrix composites

International Nuclear Information System (INIS)

Zhang Xiuqing; Liao Lihua; Ma Naiheng; Wang Haowei

2006-01-01

Magnesium matrix composites reinforced with TiC particulates was synthesized using in situ synthesis technique. The result of XRD revealed the presence of TiC in precursor blocks and TiC/AZ91 composites. Effect of aging hardening on the composites was described using Brinell hardness measurements and scanning electron microscopy (SEM). The results revealed that the aging hardening peak of TiC/AZ91 composite appeared earlier comparatively with that of AZ91 magnesium alloy. And the appearance of aging hardening peak was earlier under the higher aging temperature such as 200 deg. C. The precipitating behavior of Mg 17 Al 12 phase in AZ91 alloy and TiC/AZ91 composites was described. Little discontinuous was discovered in the composites, and the amount of continuous precipitate in the composite matrix is smaller comparatively to that of AZ91 alloy. These results were analyzed with the fine grain size, much more interface between TiC and magnesium and high-density dislocation in magnesium matrix, which was contributed to the addition of TiC particulates

Application of submerged induction hardening; Ekichu koshuha yakiire no jitsuyoka

Energy Technology Data Exchange (ETDEWEB)

Nishimori, Y; Nagai, Y; Amii, Y [Mazda Motor Corp., Hiroshima (Japan); Tanaka, Y [Netsuren Co. Ltd., Tokyo (Japan); Mizuma, T [Toyo Advanced Technologies Co. Ltd., Hiroshima (Japan)

1997-10-01

As a cost-cutting measure, the linerless diesel engine was adopted by applying submerged induction hardening process which can harden partial inner surface of cylinder block bore. In applying this process, (1) development of induction coil which can form any shape of quenched pattern and (2) the development of machining technology which can hone precisely the distorted bore after quenching, were important. With these improvements, submerged Induction hardening was made practical. 1 ref., 11 figs.

Effect of Nonlinear Hardening of Lead Rubber Bearing on Long Term Behavior of Base Isolated Containment Building

International Nuclear Information System (INIS)

Park, Junhee; Choun, Young-Sun; Kim, Min-Kyu

2015-01-01

The rubber material used in laminated rubber bearings is the hyper elastic material whose stress-strain relationship can be defined as nonlinearly elastic. From the previous research, it was presented that the rubber hardness and stiffness was increased by the aging of LRB. The mechanical properties of LRB changed by aging can directly affect a nonlinear hardening behavior. Therefore it is needed to consider the nonlinear hardening effect for exactly evaluating the seismic safety of base isolated structure during the life time. In this study, the seismic response analysis of base isolated containment building was performed by using the bilinear model and the hardening model to identify the effect of structural response on the nonlinear hardening behavior of isolator. Moreover the floor response spectrum of base isolated structure considering the aging was analyzed by according to the analysis model of LRB.. The hardening behavior of lead rubber bearing occurs at high strain. Therefore it is reasonable to assume that the hysteretic model of LRB is the nonlinear hardening model for exactly evaluating the seismic response of base isolated structure. The nonlinear analysis of base isolated containment was performed by using the nonlinear hardening variables which was resulted from the test results and finite element analysis. From the analysis results, it was represented that the FRS was higher about 40% with nonlinear hardening model than with the bilinear model. Therefore the seismic response of base isolated structure with bilinear model can be underestimated than the real response. It is desired that the nonlinear hardening model of LRB is applied for the seismic risk evaluation requiring the ultimate state of LRB

Plastic limit pressure of spherical vessels with combined hardening involving large deformation

International Nuclear Information System (INIS)

Leu, S.-Y.; Liao, K.-C.; Lin, Y.-C.

2014-01-01

The paper aims to investigate plastic limit pressure of spherical vessels of nonlinear combined isotropic/kinematic hardening materials. The Armstrong-Frederick kinematic hardening model is adopted and the Voce hardening law is incorporated for isotropic hardening behavior. Analytically, we extend sequential limit analysis to deal with combined isotropic/kinematic hardening materials. Further, exact solutions of plastic limit pressure were developed analytically by conducting both static and kinematic limit analysis. The onset of instability was also derived and solved iteratively by Newton's method. Numerically, elastic–plastic analysis is also performed by the commercial finite-element code ABAQUS incorporated with the user subroutine UMAT implemented with user materials of combined hardening. Finally, the problem formulation and the solution derivations presented here are validated by a very good agreement between the numerical results of exact solutions and the results of elastic–plastic finite-element analysis by ABAQUS. -- Highlights: • Sequential limit analysis is extended to consider combined hardening. • Exact solutions of plastic limit pressure are developed. • The onset of instability of a spherical vessel is derived and solved numerically

Origin of honeycombs: Testing the hydraulic and case hardening hypotheses

Science.gov (United States)

Bruthans, Jiří; Filippi, Michal; Slavík, Martin; Svobodová, Eliška

2018-02-01

Cavernous weathering (cavernous rock decay) is a global phenomenon, which occurs in porous rocks around the world. Although honeycombs and tafoni are considered to be the most common products of this complex process, their origin and evolution are as yet not fully understood. The two commonly assumed formation hypotheses - hydraulic and case hardening - were tested to elucidate the origin of honeycombs on sandstone outcrops in a humid climate. Mechanical and hydraulic properties of the lips (walls between adjacent pits) and backwalls (bottoms of pits) of the honeycombs were determined via a set of established and novel approaches. While the case hardening hypothesis was not supported by the determinations of either tensile strength, drilling resistance or porosity, the hydraulic hypothesis was clearly supported by field measurements and laboratory tests. Fluorescein dye visualization of capillary zone, vapor zone, and evaporation front upon their contact, demonstrated that the evaporation front reaches the honeycomb backwalls under low water flow rate, while the honeycomb lips remain dry. During occasional excessive water flow events, however, the evaporation front may shift to the lips, while the backwalls become moist as a part of the capillary zone. As the zone of evaporation corresponds to the zone of potential salt weathering, it is the spatial distribution of the capillary and vapor zones which dictates whether honeycombs are created or the rock surface is smoothed. A hierarchical model of factors related to the hydraulic field was introduced to obtain better insights into the process of cavernous weathering.

Martensitic transformations, structure, and strengthness of processed high-nitrogen and high-carbon ferrous alloys

Science.gov (United States)

Kaputkina, L. M.; Prokoshkina, V. G.

2003-10-01

Structures and properties of metastable austenitic alloys Fe-18Cr-16Ni-I2Mn-(0.17 to 0. 50)N, Fe-18Cr-12Mn-(0.48 to 1.12)N, Fe-18Cr-(0.1 to 1.18)N, and Fe-(12 to 20)Ni-(0.6 to 1.3)C, Fe-(6 to 8)Mn-(0.6 to 1.0)C, Fe-(5 to 6)Cr-(4 to 5)Mn-(0.6 to 0.8)C, Fe-6Cr-(1.0 to 1.3)C resulting from martensitic transformations under cooling and cold deformation (CD), as well as following tempering processes, were studied by magnetometry, X-ray and electron microscopy analyses, hardness measurements and mechanical properties tests. Martensite with a b.c.t. lattice was formed in all alloys with M_s{>}-196^circC during cooling. Under CD transformations of γ{to}α, γ{to}\\varepsilon{to}α, or γ{to}\\varepsilon types were realized depending on the alloy composition. Carbon increased but nitrogen decreased stacking fault energy. Thus carbon assists α-martensite formation but nitrogen promotese. As CD level and/or concentration of carbon and nitrogen increase residual stresses resulting from the CD also increase. The martensitic transformation during CD can decrease the residual stresses. Kinetic of tempering of b.c.t. thermal martensite differs from those of CD-induced martensite. In the second case, deformation aging, texture, and residual stresses are more visible. The maximal strengthening under CD takes place in (Mn+N)-steels. (Cr+N) and (Cr+Mn+N)-steels are high-strength, non-magnetic and corrosion resistant and are easily hardened by a low level of plastic deformation.

Kinematic Hardening: Characterization, Modeling and Impact on Springback Prediction

International Nuclear Information System (INIS)

Alves, J. L.; Bouvier, S.; Jomaa, M.; Billardon, R.; Oliveira, M. C.; Menezes, L. F.

2007-01-01

The constitutive modeling of the materials' mechanical behavior, usually carried out using a phenomenological constitutive model, i.e., a yield criterion associated to the isotropic and kinematic hardening laws, is of paramount importance in the FEM simulation of the sheet metal forming processes, as well as in the springback prediction. Among others, the kinematic behavior of the yield surface plays an essential role, since it is indispensable to describe the Bauschinger effect, i.e., the materials' answer to the multiple tension-compression cycles to which material points are submitted during the forming process. Several laws are usually used to model and describe the kinematic hardening, namely: a) the Prager's law, which describes a linear evolution of the kinematic hardening with the plastic strain rate tensor b) the Frederick-Armstrong non-linear kinematic hardening, basically a non-linear law with saturation; and c) a more advanced physically-based law, similar to the previous one but sensitive to the strain path changes. In the present paper a mixed kinematic hardening law (linear + non-linear behavior) is proposed and its implementation into a static fully-implicit FE code is described. The material parameters identification for sheet metals using different strategies, and the classical Bauschinger loading tests (i.e. in-plane forward and reverse monotonic loading), are addressed, and their impact on springback prediction evaluated. Some numerical results concerning the springback prediction of the Numisheet'05 Benchmark no. 3 are briefly presented to emphasize the importance of a correct modeling and identification of the kinematic hardening behavior

Influence of cobalt, tantaum and tungsten on the high temperature mechanical properties of single crystal nickel-base superalloys. Ph.D. Thesis - Case Western Reserve Univ.

Science.gov (United States)

Nathal, M. V.

1984-01-01

For alloys with the baseline refractory metal level of 3 percent Ta and 10 percent W, decreases in Co level from 10 to 0 percent resulted in increased tensile strength and creep resistance. Substitution of W for Ta resulted in decreased creep life at high stresses but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta plus W totals, strength was independent of Co level. The increases in tensile strength with increases in refractory metal content were related to the increases in gamma volume fraction and solid solution hardening. Increases in strength as Co level decreased were considered to be the result of coherency strain hardening from the increased lattice mismatch. Dislocation shear through the gamma-gamma interface is considered to be the rate limiting step in the deformation process.

Advanced high strength steels for automotive industry

Energy Technology Data Exchange (ETDEWEB)

Galan, J.; Samek, L.; Verleysen, P.; Verbeken, K.; Houbert, Y.

2012-11-01

The car industry is facing pressure because of the growing demand for more fuel-efficient passenger cars. In order to limit energy consumption and air pollution the weight of the car body has to be reduced. At the same time, high levels of safety have to be guaranteed. In this situation, the choice of material becomes a key decision in car design. As a response to the requirements of the automotive sector, high strength steels and advanced high strength steels have been developed by the steel industry. These modern steel grades offer an excellent balance of low cost, light weight and mechanical properties. (Author) 48 refs.

Engineering Performance of High Strength Concrete Containing Steel Fibre Reinforcement

Directory of Open Access Journals (Sweden)

Md Azree Othuman Mydin

2013-09-01

Full Text Available The development and utilization of the high strength concrete in the construction industry have been increasing rapidly. Fiber reinforced concrete is introduced to overcome the weakness of the conventional concrete because concrete normally can crack under a low tensile force and it is known to be brittle. Steel fibre is proved to be the popular and best combination in the high strength concrete to result the best in the mechanical and durability properties of high strength concrete with consideration of curing time, steel fibre geometry, concrete grade and else more. The incorporation of steel fibre in the mortar mixture is known as steel fibre reinforced concrete have the potential to produce improvement in the workability, strength, ductility and the deformation of high strength concrete. Besides that, steel fibre also increases the tensile strength of concrete and improves the mechanical properties of the steel fibre reinforced concrete. The range for any high strength concrete is between 60MPa-100MPa. Steel fibre reinforced concrete which contains straight fibres has poorer physical properties than that containing hooked end stainless steel fibre due to the length and the hooked steel fibre provide a better effective aspects ratio. Normally, steel fibre tensile strength is in the range of 1100MPa-1700MPa. Addition of less steel fibre volumes in the range of 0.5% to 1.0% can produce better increase in the flexural fatigue strength. The strength can be increased with addition of steel fibre up to certain percentage. This paper will review and present some basic properties of steel fibre reinforced concrete such as mechanical, workability and durability properties.

A project of X-ray hardening correction in large ICT

International Nuclear Information System (INIS)

Fang Min; Liu Yinong; Ni Jianping

2005-01-01

This paper presents a means of polychromatic X-ray beam hardening correction using a standard function to transform the polychromatic projection to monochromatic projection in large Industrial Computed Tomography (ICT). Some parameters were defined to verify the validity of hardening correction in large ICT and optimized. Simulated experiments were used to prove that without prior knowledge of the composition of the scanned object, the correction method using monochromatic reconstruction arithmetic could remove beam hardening artifact greatly. (authors)

Influence of Hardening Model on Weld Residual Stress Distribution

Energy Technology Data Exchange (ETDEWEB)

Mullins, Jonathan; Gunnars, Jens (Inspecta Technology AB, Stockholm (Sweden))

2009-06-15

This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

Influence of Hardening Model on Weld Residual Stress Distribution

International Nuclear Information System (INIS)

Mullins, Jonathan; Gunnars, Jens

2009-06-01

This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

Plasma nitriding - an eco friendly surface hardening process

International Nuclear Information System (INIS)

Mukherjee, S.

2015-01-01

Surface hardening is a process of heating the metal such that the surface gets only hardened. This process is adopted for many components like gears, cams, and crankshafts, which desire high hardness on the outer surface with a softer core to withstand the shocks. So, to attain such properties processes like carburising, nitriding, flame hardening and induction hardening are employed. Amongst these processes nitriding is the most commonly used process by many industries. In nitriding process the steel material is heated to a temperature of around 550 C and then exposed to atomic nitrogen. This atomic nitrogen reacts with iron and other alloying elements and forms nitrides, which are very hard in nature. By this process both wear resistance and hardness of the product can be increased. The atomic nitrogen required for this process can be obtained using ammonia gas (gas nitriding), cyanide based salt bath (liquid nitriding) and plasma medium (plasma nitriding). However, plasma nitriding has recently received considerable industrial interest owing to its characteristic of faster nitrogen penetration, short treatment time, low process temperature, minimal distortion, low energy use and easier control of layer formation compared with conventional techniques such as gas and liquid nitriding. This process can be used for all ferrous materials including stainless steels. Plasma nitriding is carried out using a gas mixture of nitrogen and hydrogen gas at sub atmospheric pressures hence, making it eco-friendly in nature. Plasma nitriding allows modification of the surface layers and hardness profiles by changing the gas mixture and temperature. The wide applicable temperature range enables a multitude of applications, beyond the possibilities of gas or salt bath processes. This has led to numerous applications of this process in industries such as the manufacture of machine parts for plastics and food processing, packaging and tooling as well as pumps and hydraulic, machine

Reducing beam hardening effects and metal artefacts using Medipix3RX: With applications from biomaterial science

CERN Document Server

Rajendran, K; de Ruiter, N J A; Chernoglazov, A I; Panta, R K; Butler, A P H; Butler, P H; Bell, S T; Anderson, N G; Woodfield, T B F; Tredinnick, S J; Healy, J L; Bateman, C J; Aamir, R; Doesburg, R M N; Renaud, P F; Gieseg, S P; Smithies, D J; Mohr, J L; Mandalika, V B H; Opie, A M T; Cook, N J; Ronaldson, J P; Nik, S J; Atharifard, A; Clyne, M; Bones, P J; Bartneck, C; Grasset, R; Schleich, N; Billinghurst, M

2014-01-01

This paper discusses methods for reducing beam hardening effects using spectral data for biomaterial applications. A small-animal spectral scanner operating in the diagnostic energy range was used. We investigate the use of photon-processing features of the Medipix3RX ASIC in reducing beam hardening and associated artefacts. A fully operational charge summing mode was used during the imaging routine. We present spectral data collected for metal alloy samples, its analysis using algebraic 3D reconstruction software and volume visualisation using a custom volume rendering software. Narrow high energy acquisition using the photon-processing detector revealed substantial reduction in beam hardening effects and metal artefacts.

Weld Design, Testing, and Assessment Procedures for High Strength Pipelines

Science.gov (United States)

2011-12-20

Long-distance high-strength pipelines are increasingly being constructed for the efficient transportation of energy products. While the high-strength linepipe steels and high productivity welding processes are being applied, the procedures employed f...

Survey of Processing Methods for High Strength High Conductivity Wires for High Field Magnet Applications

Energy Technology Data Exchange (ETDEWEB)

Han, K.; Embury, J.D.

1998-10-01

This paper will deal with the basic concepts of attaining combination of high strength and high conductivity in pure materials, in-situ composites and macrocomposites. It will survey current attainments, and outline where some future developments may lie in developing wire products that are close to the theoretical strength of future magnet applications.

Survey of Processing Methods for High Strength High Conductivity Wires for High Field Magnet Applications

International Nuclear Information System (INIS)

Han, K.; Embury, J.D.

1998-01-01

This paper will deal with the basic concepts of attaining combination of high strength and high conductivity in pure materials, in-situ composites and macrocomposites. It will survey current attainments, and outline where some future developments may lie in developing wire products that are close to the theoretical strength of future magnet applications

Tensile deformation behavior and deformation twinning of an equimolar CoCrFeMnNi high-entropy alloy

Energy Technology Data Exchange (ETDEWEB)

Joo, S.-H.; Kato, H. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Jang, M.J.; Moon, J. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of); Tsai, C.W.; Yeh, J.W. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Kim, H.S., E-mail: hskim@postech.ac.kr [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of); Center for High Entropy Alloys, Pohang University of Science and Technology, Pohang 37673 (Korea, Republic of)

2017-03-24

The tensile deformation and strain hardening behaviors of an equimolar CoCrFeMnNi high-entropy alloy (HEA) were investigated and compared with low and medium entropy equiatomic alloys (LEA and MEA). The HEA had a lower yield strength than the MEA because the addition of Mn weakens solid solution hardening in the HEA. However, deformation twinning induced the multiple stage strain hardening behavior of the HEA and enhanced strength and elongation. Using tensile-interrupted electron backscatter diffraction analysis, geometrically necessary dislocations were observed as plume-shaped features in grain interior, and a considerable texture was characterized, which is typical of face centered cubic metals. Moreover, the relationship between favorably oriented grains and twinning in the HEA bore a clear resemblance to the same tendency in TWIP steels. The thickness of the twin bundles was less than 100 nm. A high density of stacking defects was found in the nanotwins. Nano twinning and stacking faults were found to contribute to the remarkable mechanical properties. Deformation induced twinning not only demonstrated the dynamic Hall-Petch effect but also changed dislocation cell substructures into microband structures.

Ultraviolet rays hardening type material which can do the repair of FRP it is easy; Kantan ni FRP no hoshu ga dekiru shigaisen kokagata zairyo

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-09-15

The seat-shaped ultraviolet rays (UV) hardening type material which the reinforcement of the fiber strengthening plastic (FRP) and the repair and the corrosion partial repair of the steel rice are made easily in is developed, is sold in late April. The same product is the seat, which made soak an UV hardening type plastic in the fiberglass. Though a un-saturation polyester plastic was adopted, as for many FRP repair materials, a tolerance to the medicine, shock, heat rose by adopting plastic, and the adhesion power became strong, too. And, because it is a seat-shaped, a hand lei rise which takes a plastic and hardening medicine in its hand and to mix is compared with the way of repairing it, and the strength of the repair point becomes uniform with constructing it easily in a short time, too. The car and the port business world are wide except for the construction, and the same company plans sales promotion. (translated by NEDO)

Concrete, hardened: Self desiccation

DEFF Research Database (Denmark)

Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard; Persson, Bertil

1999-01-01

The test method covers the determination of internal relative humidity (RH) in hardened concrete and cement mortar using RH instruments. The determination of RH is done on crushed samples of concrete or cement motar. This test method is only for measuring equipment which gives off or takes up...

Radiation-hardened CMOS/SOS LSI circuits

International Nuclear Information System (INIS)

Aubuchon, K.G.; Peterson, H.T.; Shumake, D.P.

1976-01-01

The recently developed technology for building radiation-hardened CMOS/SOS devices has now been applied to the fabrication of LSI circuits. This paper describes and presents results on three different circuits: an 8-bit adder/subtractor (Al gate), a 256-bit shift register (Si gate), and a polycode generator (Al gate). The 256-bit shift register shows very little degradation after 1 x 10 6 rads (Si), with an increase from 1.9V to 2.9V in minimum operating voltage, a decrease of about 20% in maximum frequency, and little or no change in quiescent current. The p-channel thresholds increase from -0.9V to -1.3V, while the n-channel thresholds decrease from 1.05 to 0.23V, and the n-channel leakage remains below 1nA/mil. Excellent hardening results were also obtained on the polycode generator circuit. Ten circuits were irradiated to 1 x 10 6 rads (Si), and all continued to function well, with an increase in minimum power supply voltage from 2.85V to 5.85V and an increase in quiescent current by a factor of about 2. Similar hardening results were obtained on the 8-bit adder, with the minimum power supply voltage increasing from 2.2V to 4.6V and the add time increasing from 270 to 350 nsec after 1 x 10 6 rads (Si). These results show that large CMOS/SOS circuits can be hardened to above 1 x 10 6 rads (Si) with either the Si gate or Al gate technology. The paper also discusses the relative advantages of the Si gate versus the Al gate technology

Beam hardening correction algorithm in microtomography images