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Sample records for deduce ductile fracture

  1. Computer simulation of ductile fracture

    International Nuclear Information System (INIS)

    Wilkins, M.L.; Streit, R.D.

    1979-01-01

    Finite difference computer simulation programs are capable of very accurate solutions to problems in plasticity with large deformations and rotation. This opens the possibility of developing models of ductile fracture by correlating experiments with equivalent computer simulations. Selected experiments were done to emphasize different aspects of the model. A difficult problem is the establishment of a fracture-size effect. This paper is a study of the strain field around notched tensile specimens of aluminum 6061-T651. A series of geometrically scaled specimens are tested to fracture. The scaled experiments are conducted for different notch radius-to-diameter ratios. The strains at fracture are determined from computer simulations. An estimate is made of the fracture-size effect

  2. Micromechanics modelling of ductile fracture

    CERN Document Server

    Chen, Zengtao

    2013-01-01

    This book summarizes research advances in micromechanics modelling of ductile fractures made in the past two decades. The ultimate goal of this book is to reach manufacturing frontline designers and materials engineers by providing a user-oriented, theoretical background of micromechanics modeling. Accordingly, the book is organized in a unique way and presents a vigorous damage percolation model developed by the authors over the last ten years. This model overcomes almost all difficulties of the existing models and can be used to completely accommodate ductile damage development within a single, measured microstructure frame. Related void damage criteria including nucleation, growth and coalescence are then discussed in detail: how they are improved, when and where they are used in the model, and how the model performs in comparison with the existing models. Sample forming simulations are provided to illustrate the model’s performance.

  3. Fracture toughness of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-12-01

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

  4. Influence of ageing, inclusions and voids on ductile fracture ...

    Indian Academy of Sciences (India)

    Unknown

    inclusions present. The initiation of voids at small particles in the ductile fracture process appears to have little effect on fracture toughness. The strain hardening capacity has a marked effect on void size, and is an indicator of fracture toughness in the commercial Al alloy. Keywords. Ageing; inclusions; voids; ductile fracture; ...

  5. Prediction of Ductile Fracture Surface Roughness Scaling

    DEFF Research Database (Denmark)

    Needleman, Alan; Tvergaard, Viggo; Bouchaud, Elisabeth

    2012-01-01

    . Ductile crack growth in a thin strip under mode I, overall plane strain, small scale yielding conditions is analyzed. Although overall plane strain loading conditions are prescribed, full 3D analyses are carried out to permit modeling of the three dimensional material microstructure and of the resulting...... three dimensional stress and deformation states that develop in the fracture process region. An elastic-viscoplastic constitutive relation for a progressively cavitating plastic solid is used to model the material. Two populations of second phase particles are represented: large inclusions with low...... strength, which result in large voids near the crack tip at an early stage, and small second phase particles, which require large strains before cavities nucleate. The larger inclusions are represented discretely and various three dimensional distributions of the larger particles are considered...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-07-01

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

  7. Study on ductile fracture evaluation for austenitic stainless steel

    International Nuclear Information System (INIS)

    Miura, Naoki; Shimakawa, Takashi; Kashima, Koichi; Michiba, Kouji; Hiramatsu, Hideki.

    1994-01-01

    In the development of Fast Breeder Reactors (FBRs), structural integrity must be assured for components subjected to high temperatures up to 550degC, even though possible defects are presumed. Nonlinear fracture mechanics is one of the most effective approaches to evaluate ductile fracture behavior of cracked components. In this study, ductile fracture tests were conducted at room temperature and 550degC for austenitic stainless steel SUS304 and 316FR, which were candidates for FBR structural material. The applicability of fracture parameters was investigated from tests using small CT specimens, small CCT specimens, and wide CCT specimens. Fracture tests under the condition of combined tension and bending loads were also performed to investigate the effect of additional bending stress due to the temperature gradient through thickness. It was ascertained that fracture load could be predicted based on the net section collapse criterion and was not so affected by an additional bending stress. (author)

  8. Impact toughness and fracture toughness of austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Jingcheng LIU

    2004-11-01

    Full Text Available The impact toughness and fracture toughness ofaustermpered ductile iron (ADI are described. The notched and un-notched charpy impact toughness of ADI at room temperature are somewhat lower than that of steel castings or forged steel pieces, however, they are approximately three times higher than that of mormal pearlitic ductile iron. The impact toughness of ADI decreases with decreasing temperature; but at -40 ℃ it still maintains about 70% of the value at room temperature. The properties of fracture toughness are important in safety design and failure analysis. In this study all fracture toughness data of ADI are higher than that of conventional ductile iron, and are equivalent to or better than that of steel castings o forged steel pieces with the tensile strength equivalent to ADI.

  9. Fracture toughness of borides formed on boronized ductile iron

    International Nuclear Information System (INIS)

    Sen, Ugur; Sen, Saduman; Koksal, Sakip; Yilmaz, Fevzi

    2005-01-01

    In this study, fracture toughness properties of boronized ductile iron were investigated. Boronizing was realized in a salt bath consisting of borax, boric acid and ferro-silicon. Boronizing heat treatment was carried out between 850 and 950 deg. C under the atmospheric pressure for 2-8 h. Borides e.g. FeB, Fe 2 B formed on ductile iron was verified by X-ray diffraction (XRD) analysis, SEM and optical microscope. Experimental results revealed that longer boronizing time resulted in thicker boride layers. Optical microscope cross-sectional observation of borided layers showed dentricular morphology. Both microhardness and fracture toughness of borided surfaces were measured via Vickers indenter. The harnesses of borides formed on the ductile iron were in the range of 1160-2140 HV 0.1 and fracture toughness were in the range of 2.19-4.47 MPa m 1/2 depending on boronizing time and temperature

  10. Numerical modeling of ductile tearing effects on cleavage fracture toughness

    International Nuclear Information System (INIS)

    Dodds, R.H. Jr.; Tang, M.; Anderson, T.L.

    1994-05-01

    Experimental studies demonstrate a significant effect of specimen size, a/W ratio and prior ductile tearing on cleavage fracture toughness values (J c ) measured in the ductile-to-brittle transition region of ferritic materials. In the lower-transition region, cleavage fracture often occurs under conditions of large-scale yielding but without prior ductile crack extension. The increased toughness develops when plastic zones formed at the crack tip interact with nearby specimen surfaces which relaxes crack-tip constraint (stress triaxiality). In the mid-to-upper transition region, small amounts of ductile crack extension (often c -values. Previous work by the authors described a micromechanics fracture model to correct measured J c -values for the mechanistic effects of large-scale yielding. This new work extends the model to also include the influence of ductile crack extension prior to cleavage. The paper explores development of the new model, provides necessary graphs and procedures for its application and demonstrates the effects of the model on fracture data sets for two pressure vessel steels (A533B and A515)

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

    Directory of Open Access Journals (Sweden)

    VYACHESLAV GORYANY

    2008-01-01

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

  12. Statistics of ductile fracture surfaces: the effect of material parameters

    DEFF Research Database (Denmark)

    Ponson, Laurent; Cao, Yuanyuan; Bouchaud, Elisabeth

    2013-01-01

    distributed. The three dimensional analysis permits modeling of a three dimensional material microstructure and of the resulting three dimensional stress and deformation states that develop in the fracture process region. Material parameters characterizing void nucleation are varied and the statistics......The effect of material parameters on the statistics of fracture surfaces is analyzed under small scale yielding conditions. Three dimensional calculations of ductile crack growth under mode I plane strain, small scale yielding conditions are carried out using an elastic-viscoplastic constitutive...... of the resulting fracture surfaces is investigated. All the fracture surfaces are found to be self-affine over a size range of about two orders of magnitude with a very similar roughness exponent of 0.56 ± 0.03. In contrast, the full statistics of the fracture surfaces is found to be more sensitive to the material...

  13. Strain rate effects on fracture behavior of Austempered Ductile Irons

    Science.gov (United States)

    Ruggiero, Andrew; Bonora, Nicola; Gentile, Domenico; Iannitti, Gianluca; Testa, Gabriel; Hörnqvist Colliander, Magnus; Masaggia, Stefano; Vettore, Federico

    2017-06-01

    Austempered Ductile Irons (ADIs), combining high strength, good ductility and low density, are candidates to be a suitable alternative to high-strength steels. Nevertheless, the concern about a low ductility under dynamic loads often leads designers to exclude cast irons for structural applications. However, results from dynamic tensile tests contradict this perception showing larger failure strain with respect to quasistatic data. The fracture behaviour of ADIs depends on damage mechanisms occurring in the spheroids of graphite, in the matrix and at their interface, with the matrix (ausferrite) consisting of acicular ferrite in carbon-enriched austenite. Here, a detailed microstructural analysis was performed on the ADI 1050-6 deformed under different conditions of strain rates, temperatures, and states of stress. Beside the smooth specimens used for uniaxial tensile tests, round notched bars to evaluate the ductility reduction with increasing stress triaxiality and tophat geometries to evaluate the propensity to shear localization and the associated microstructural alterations were tested. The aim of the work is to link the mechanical and fracture behavior of ADIs to the load condition through the microstructural modifications that occur for the corresponding deformation path.

  14. Analysis Strategy for Fracture Assessment of Defects in Ductile Materials

    International Nuclear Information System (INIS)

    Dillstroem, Peter; Andersson, Magnus; Sattari-Far, Iradj; Weilin Zang

    2009-06-01

    The main purpose of this work is to investigate the significance of the residual stresses for defects (cracks) in ductile materials with nuclear applications, when the applied primary (mechanical) loads are high. The treatment of weld-induced stresses as expressed in the SACC/ProSACC handbook and other fracture assessment procedures such as the ASME XI code and the R6-method is believed to be conservative for ductile materials. This is because of the general approach not to account for the improved fracture resistance caused by ductile tearing. Furthermore, there is experimental evidence that the contribution of residual stresses to fracture diminishes as the degree of yielding increases to a high level. However, neglecting weld-induced stresses in general, though, is doubtful for loads that are mostly secondary (e.g. thermal shocks) and for materials which are not ductile enough to be limit load controlled. Both thin-walled and thick-walled pipes containing surface cracks are studied here. This is done by calculating the relative contribution from the weld residual stresses to CTOD and the J-integral. Both circumferential and axial cracks are analysed. Three different crack geometries are studied here by using the finite element method (FEM). (i) 2D axisymmetric modelling of a V-joint weld in a thin-walled pipe. (ii) 2D axisymmetric modelling of a V-joint weld in a thick-walled pipe. (iii) 3D modelling of a X-joint weld in a thick-walled pipe. t. Each crack configuration is analysed for two load cases; (1) Only primary (mechanical) loading is applied to the model, (2) Both secondary stresses and primary loading are applied to the model. Also presented in this report are some published experimental investigations conducted on cracked components of ductile materials subjected to both primary and secondary stresses. Based on the outcome of this study, an analysis strategy for fracture assessment of defects in ductile materials of nuclear components is proposed. A new

  15. Ductile fracture estimation of reactor pressure vessel under thermal shock

    International Nuclear Information System (INIS)

    Takahashi, Jun; Sakai, Shinsuke; Okamura, Hiroyuki

    1990-01-01

    This paper presents a new scheme for the estimation of unstable ductile fracture of a reactor pressure vessel under thermal shock conditions. First, it is shown that the bending moment applied to the cracked section can be evaluated by considering the plastic deformation of the cracked section and the thermal deformation of the shell. As the contribution of the local thermal stress to the J-value is negligible, the J-value under thermal shock can be easily evaluated by using fully plastic solutions for the cracked part. Next, the phenomena of ductile fracture under thermal shock are expressed on the load-versus-displacement diagram which enables us to grasp the transient phenomena visually. In addition, several parametrical surveys are performed on the above diagram concerning the variation of (1) thermal shock conditions, (2) initial crack length, and (3) J-resistance curve (i.e. embrittlement by neutron irradiation). (author)

  16. Texture evaluation in ductile fracture process by neutron diffraction measurement

    Science.gov (United States)

    Sunaga, H.; Takamura, M.; Ikeda, Y.; Otake, Y.; Hama, T.; Kumagai, M.; Suzuki, H.; Suzuki, S.

    2016-08-01

    A neutron diffraction measurement was performed to reveal microstructural aspects of the ductile fracture in ferritic steel. The diffraction patterns were continuously measured at the center of the reduced area while a tensile specimen was loaded under tension until the end of the fracture process. The measurement results showed that the volume fraction of (110)-oriented grains increased when the texture evolved as a result of plastic deformation. But the mechanism of texture evolution may be changed during necking, decreasing an increase rate of the volume fraction.

  17. Crack and fracture behaviour in tough ductile materials

    International Nuclear Information System (INIS)

    Venter, R.D.; Hoeppner, D.W.

    1985-10-01

    The report describes various approaches and developments pertaining to the understanding of crack and fracture behaviour in tough ductile materials. The fundamental elastic fracture mechanics concepts based on the concepts of energy, stress field, and displacement are introduced and their interrelationships demonstrated. The extension of these concepts to include elasto-plastic fracture mechanics considerations is reviewed in the context of the preferred options available for the development of appropriate design methodologies. The recommendations of the authors are directed towards the continued development of the J-integral concept. This energy-based concept, in its fundamental form, has a sound theoretical basis and as such offers the possibility of incorporating elasto-plastic fracture mechanics considerations in the crack and fracture behaviour of tough ductile materials. It must however be emphasized that the concise defintion of J becomes increasingly suspect as the crack length increases. J is not a material property, as is J IC , but emerges as a useful empirical parameter which is dependent upon the particular geometry and the loading imposed on the structure. It is proposed that 'lowest bound' J-resistance curves and the associated J-T curves be experimentally developed and employed in the design process. Improvements to these 'lowest bounds' can be developed through extensive analysis of the twin J-CTOA criteria and validation of this approach through near full scale tests

  18. Hot ductility and fracture mechanisms of a structural steel

    International Nuclear Information System (INIS)

    Calvo, J.; Cabrera, J. M.; Prado, J. M.

    2006-01-01

    The hot ductility of a structural steel produced from scrap recycling has been studied to determine the origin of the transverse cracks in the corners that appeared in some billets. Samples extracted both from a billet with transverse cracks and from a billet with no external damage were tested. To evaluate the influence of residual elements and inclusions, the steel was compared to another one impurity free. Reduction in area of the samples tensile tested to the fracture was taken as a measure of the hot ductility. The tests were carried out at temperatures ranging from 1000 degree centigree to 650 degree centigree and at a strain rate of 1.10-3 s-1. The fracture surfaces of the tested samples were observed by scanning electron microscopy in order to determine the embrittling mechanisms that could be acting. The steel with residuals and impurities exhibited lower ductility values for a wider temperature range than the clean steel. The embrittling mechanisms also changed as compared to the impurity free steel. (Author)

  19. Effect of inclusion density on ductile fracture toughness and roughness

    DEFF Research Database (Denmark)

    Srivastava, Akhilesh Kumar; Ponson, L.; Osovski, S.

    2014-01-01

    that result in void nucleation at an early stage are modeled discretely while smaller particles that require large strains to nucleate voids are homogeneously distributed. Full field solutions are obtained for eight volume fractions, ranging from 1% to 19%, of randomly distributed larger inclusions. For each...... on the inclusion volume fraction. Consideration of the full statistics of the fracture surface roughness revealed other parameters that vary with inclusion volume fraction. For smaller values of the discretely modeled inclusion volume fraction (≤7%), there is a linear correlation between several measures......Three dimensional calculations of ductile fracture under mode I plane strain, small scale yielding conditions are carried out using an elastic-viscoplastic constitutive relation for a progressively cavitating solid with two populations of void nucleating second phase particles. Larger inclusions...

  20. Fracture Toughness Improvement of Composites Reinforced with Optimally Shaped Short Ductile Fibers

    National Research Council Canada - National Science Library

    Wetherhold, Robert C; Patra, Abani K

    2001-01-01

    The fracture toughness of brittle matrix composites reinforced with ductile fibers has been greatly improved by shaping the fibers so that they fully contribute their plastic work to the fracture process...

  1. The effect of loading rate on ductile fracture toughness and fracture surface roughness

    DEFF Research Database (Denmark)

    Osovski, S.; Srivastava, Akhilesh Kumar; Ponson, L.

    2015-01-01

    The variation of ductile crack growth resistance and fracture surface roughness with loading rate is modeled under mode I plane strain, small scale yielding conditions. Three-dimensional calculations are carried out using an elastic-viscoplastic constitutive relation for a progressively cavitatin...

  2. Diagnosis of the Fracture and Fracture Energy of High-Ductility Steels in Instrumented Impact-Bending Tests

    Science.gov (United States)

    Farber, V. M.; Khotinov, V. A.; Morozova, A. N.; Lezhnin, N. V.; Martin, T.

    2015-09-01

    Fractures and their profiles are diagnosed by macro- and micro-fractographic analysis after impact bending tests of Charpy specimens of a high-ductility steel of strength class X80. The results of the analysis of fracture surfaces and fracture diagrams are used to determine the unit amount of energy expended on ductile fracture in various zones in terms of the average length of the ridges (bridges) in the microstructure.

  3. Ductile fracture assessment using parameters from small specimens

    Energy Technology Data Exchange (ETDEWEB)

    Talja, H. [VTT Manufacturing Technology, Espoo (Finland)

    1998-12-31

    The topic of this thesis is the computational aspects in the assessment of ductile failure in metals. The first part briefly describes the micromechanics of ductile crack growth and methods for assessing it. The `classic` approach to describe material behaviour using fracture mechanics is summarised. The limitations of the one parameter approach based on the stress intensity factor K or the J- integral are described. Attempts to extend the application field of fracture mechanics parameters by introducing triaxility or constraint parameters are also presented. Different local approach methodologies are summarised. Special attention is paid to the modified Gurson model, which is based on micro-mechanical studies of void initiation, growth and coalescence. The main part of the work consists of numerical analyses with the modified Gurson model. The parameters of the model are first determined by matching tensile test results by finite element analysis, and then applied to J-R curve prediction. This methodology is applied to several reactor pressure vessel materials: A533B, 20 MnMoNi 5 5 and austenitic VVER 440 cladding. As a result, the applicability of different specimen types for the parameter determination of the modified Gurson model has been evaluated. Because a combination of experimental and numerical work is needed, it proved to be most feasible to use specimens which can be simulated with two-dimensional or axisymmetric finite element models. Further, a practical way to treat anisotropic material behaviour using the modified Gurson model by using separate parameter sets for different orientations has been proposed and verified. The correspondence between the observed scatters in tensile and fracture mechanical test results has been examined. Best agreement was obtained fitting the scatter of tensile tests by varying the values of initial parameters. Reasons for apparently higher ductility measured from sub-sized than standard size tensile specimens were

  4. Ductile Fracture Behaviour of Hot Isostatically Pressed Inconel 690 Superalloy

    Science.gov (United States)

    Cooper, A. J.; Brayshaw, W. J.; Sherry, A. H.

    2018-01-01

    Herein we assess the differences in Charpy impact behavior between Hot Isostatically Pressed and forged Inconel 690 alloy over the temperature range of 300 °C to - 196 °C. The impact toughness of forged 690 exhibited a relatively small temperature dependence, with a maximum difference of ca. 40 J measured between 300 °C and - 196 °C, whereas the HIP'd alloy exhibited a difference of approximately double that of the forged alloy over the same temperature range. We have conducted Charpy impact testing, tensile testing, and metallographic analyses on the as-received materials as well as fractography of the failed Charpy specimens in order to understand the mechanisms that cause the observed differences in material fracture properties. The work supports a recent series of studies which assess differences in fundamental fracture behavior between Hot Isostatically Pressed and forged austenitic stainless steel materials of equivalent grades, and the results obtained in this study are compared to those of the previous stainless steel investigations to paint a more general picture of the comparisons between HIP vs forged material fracture behavior. Inconel 690 was selected in this study since previous studies were unable to completely omit the effects of strain-induced martensitic transformation at the tip of the Chary V-notch from the fracture mechanism; Inconel 690 is unable to undergo strain-induced martensitic transformation due to the alloy's high nickel content, thereby providing a sister study with the omission of any martensitic transformation effects on ductile fracture behavior.

  5. Quantification of damage evolution for a micromechanical model of ductile fracture in spallation of tantalum

    Energy Technology Data Exchange (ETDEWEB)

    Zurek, A.K.; Thissell, W.R.; Tonks, D.L.; Hixon, R.; Addessio, F.

    1997-05-01

    The authors present quantification of micromechanical features such as voids that comprise the ductile fracture obtained under uniaxial strain condition in a spall test of commercial purity tantalum. Two evolutionary parameters of ductile fracture void formation are quantified: (i) the void volume fraction (porosity) and its distribution with respect to the distance from the main spall fracture plane, and (ii) void diameter distribution. The results complement the discussion of the implications of void clustering and linking for micromechanical modeling of ductile fracture as presented in a paper by D. L. Tonks et al. in this volume.

  6. A multi-surface plasticity model for ductile fracture simulations

    Science.gov (United States)

    Keralavarma, Shyam M.

    2017-06-01

    The growth and coalescence of micro-voids in a material undergoing ductile fracture depends strongly on the loading path. Void growth occurs by diffuse plasticity in the material and is sensitive to the hydrostatic stress, while void coalescence occurs by the localization of plastic deformation in the inter-void ligaments under a combination of normal and shear stresses on the localization plane. In this paper, a micromechanics-based plasticity model is developed for an isotropic porous material, accounting for both diffuse and localized modes of plasticity at the micro-scale. A multi-surface approach is adopted, and two existing plasticity models that separately account for the two modes of yielding, above, are synthesized to propose an effective isotropic yield criterion and associated state evolution equations. The yield criterion is validated by comparison with quasi-exact numerical yield loci computed using a finite elements based limit analysis procedure. It is shown that the new criterion is in better agreement with the numerical loci than the Gurson model, particularly for large values of the porosity for which the loading path dependence of the yield stress is well predicted by the new model. Even at small porosities, it is shown that the new model predicts marginally lower yield stresses under low triaxiality shear dominated loadings compared to the Gurson model, in agreement with the numerical limit analysis data. Predictions for the strains to the onset of coalescence under proportional loading, obtained by numerically integrating the model, indicate that void coalescence tends to occur at relatively small plastic strain and porosity levels under shear dominated loadings. Implications on the prediction of ductility using the new model in fracture simulations are discussed.

  7. Fracture mechanisms in multilayer phosphorene assemblies: from brittle to ductile.

    Science.gov (United States)

    Liu, Ning; Hong, Jiawang; Zeng, Xiaowei; Pidaparti, Ramana; Wang, Xianqiao

    2017-05-24

    The outstanding mechanical performance of nacre has stimulated numerous studies on the design of artificial nacres. Phosphorene, a new two-dimensional (2D) material, has a crystalline in-plane structure and non-bonded interaction between adjacent flakes. Therefore, multi-layer phosphorene assemblies (MLPs), in which phosphorene flakes are piled up in a staggered manner, may exhibit outstanding mechanical performance, especially exceptional toughness. Therefore, molecular dynamics simulations are performed to study the dependence of the mechanical properties on the overlap distance between adjacent phosphorene layers and the number of phosphorene flakes per layer. The results indicate that when the flake number is equal to 1, a transition of fracture patterns is observed by increasing the overlap distance, from a ductile failure controlled by interfacial friction to a brittle failure dominated by the breakage of covalent bonds inside phosphorene flakes. Moreover, the failure pattern can be tuned by changing the number of flakes in each phosphorene layer. The results imply that the ultimate strength follows a power law with the exponent -0.5 in terms of the flake number, which is in good agreement with our analytical model. Furthermore, the flake number in each phosphorene layer is optimized as 2 when the temperature is 1 K in order to potentially achieve both high toughness and strength. Moreover, our results regarding the relations between mechanical performance and overlap distance can be explained well using a shear-lag model. However, it should be pointed out that increasing the temperature of MLPs could cause the transition of fracture patterns from ductile to brittle. Therefore, the optimal flake number depends heavily on temperature to achieve both its outstanding strength and toughness. Overall, our findings unveil the fundamental mechanism at the nanoscale for MLPs as well as provide a method to design phosphorene-based structures with targeted properties

  8. Effects of Silicon on Mechanical Properties and Fracture Toughness of Heavy-Section Ductile Cast Iron

    Directory of Open Access Journals (Sweden)

    Liang Song

    2015-01-01

    Full Text Available The effects of silicon (Si on the mechanical properties and fracture toughness of heavy-section ductile cast iron were investigated to develop material for spent-nuclear-fuel containers. Two castings with different Si contents of 1.78 wt.% and 2.74 wt.% were prepared. Four positions in the castings from the edge to the center, with different solidification cooling rates, were chosen for microstructure observation and mechanical properties’ testing. Results show that the tensile strength, elongation, impact toughness and fracture toughness at different positions of the two castings decrease with the decrease in cooling rate. With an increase in Si content, the graphite morphology and the mechanical properties at the same position deteriorate. Decreasing cooling rate changes the impact fracture morphology from a mixed ductile-brittle fracture to a brittle fracture. The fracture morphology of fracture toughness is changed from ductile to brittle fracture. When the Si content exceeds 1.78 wt.%, the impact and fracture toughness fracture morphology transforms from ductile to brittle fracture. The in-situ scanning electronic microscope (SEM tensile experiments were first used to observe the dynamic tensile process. The influence of the vermicular and temper graphite on fracture formation of heavy section ductile iron was investigated.

  9. Fracture dynamics of a propagating crack in a pressurized ductile cylinder

    International Nuclear Information System (INIS)

    Emery, A.F.; Love, W.J.; Kobayashi, A.S.

    1977-01-01

    A suddenly-introduced axial through-crack in the wall of a pipe pressurized by hot water is allowed to propagate according to Weiss' notch-strength theory of ductile static fracture. The dynamic-fracture criterion used enabled the authors to obtain a unique comparison of the results of ductile-fracture with those of brittle-fracture in a fracturing A533B steel pipe. Since the pipe cross-sectional area is likely to increase with large flap motions under ductile tearing, a large deformation shell-finite-difference-dynamic-code which includes rotary inertia was used in this analysis. The uniaxial-stress-strain curve of A533B steel was approximated by a bilinear-stress-strain where Von-Mises yield criterion and associated flow rule were used in the elastic-plastic analysis. The fluid pressure was assumed constant and thus pipe flaps are only lightly loaded by pressure in this analysis. (Auth.)

  10. Fracture dynamics of a propagating crack in a pressurized ductile cylinder

    International Nuclear Information System (INIS)

    Emery, A.F.; Love, W.J.; Kobayashi, A.S.

    1977-01-01

    A suddenly-introduced axial through-crack in the wall of a pipe pressurized by hot water is allowed to propagate according to Weiss' notch-strength theory of ductile static fracture. For this somewhat ductile material of A533B steel, Weiss' criterion was extended of dynamic fracture without modification. This dynamic-fracture criterion enabled a unique comparison to be obtained for the results of ductile-fracture with those of brittle-fracture in a fracturing A533B steel pipe. Since the pipe cross-sectional area is likely to increase with large flap motions under ductile tearing, a large deformation-shell-finite-difference-dynamic-code which includes rotary inertia was used in this analysis. The uniaxial-stress-strain curve of A533B steel was approximated by a bilinear stress-strain where Von-Misses yield criterion and associated flow rule were used in the elastic-plastic analysis. The fluid pressure was assumed constant and thus pipe flaps are only lightly loaded by pressure in this analysis. In previous publications, the authors have compared their preliminary results for the shell motion obtained through their model for a fracturing pipe with those of Kanninen, et al., and Freund, et al., to evaluate the effects of pressure loading on the crack flaps and the differences between small and large deflection results. In this paper, the differences in crack-propagation behavior of a fracturing pipe composed of the same A533B but subjected to a brittle or a ductile-fracture criterion are discussed. An important conclusion in fracture dynamics derived from analyses is that a smoothly-varying crack velocity will require a non-unique crack-velocity-versus-dynamic-fracture-parameter-relation while a unique and smoothly-varying crack-velocity-versus-dynamic-fracture-parameter-relation will demand an intermittently-propagating crack

  11. Analysis by AUGER spectroscopy of type 65/35 alpha brass ductile fracture

    International Nuclear Information System (INIS)

    Monteiro, S.N.; Losch, W.H.P.

    1983-01-01

    The ductile fracture of a type 65/35 alpha brass tested in tension at room temperature has been studied inside the ultra high vacuum chamber of an AUGER/SCANNING/MICRO-PROBE equipment. The fracture characteristics of small specimens tensile deformed in a specially design apparatus were registred in terms of the morphological aspects and quantitative participation of elements. It was seen that ductile fracture is associated with Zns inclusions which separate from the Pb rich alloy interface. Regions without inclusions but with Pb segregation are possible sites favorable to the fracure propagation. (Author) [pt

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

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P. Prasad; Putatunda, Susil K

    2003-05-25

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

  13. A study on the ductile fracture of a surface crack, 1

    International Nuclear Information System (INIS)

    Kikuchi, Masanori; Nishio, Tamaki; Yano, Kazunori; Machida, Kenji; Miyamoto, Hiroshi

    1988-01-01

    Ductile fracture of surface crack is studied experimentally and numerically. At first, fatigue pre-crack is introduced, and the aspect ratios of the growing fatigue crack are measured. Then the ductile fracture test is carried out and the distributions of SZW and Δa are measured. It is noted that Δa is largest where φ, the angle from surface, is nearly 30deg. J integral distribution is evaluated by the finite element method, and it is shown that the J value is also the largest where φ is nearly 30deg. (author)

  14. A rate-dependent Hosford-Coulomb model for predicting ductile fracture at high strain rates

    Directory of Open Access Journals (Sweden)

    Marcadet Stephane J.

    2015-01-01

    Full Text Available The Hosford-Coulomb model incorporates the important effect of the Lode angle parameter in addition to the stress triaxiality to predict the initiation of ductile fracture. A strain-rate dependent extension of the Hosford-Coulomb model is presented to describe the results from low, intermediate and high strain rate fracture experiments on advanced high strength steels (DP590 and TRIP780. The model predictions agree well with the experimental observation of an increase in ductility as function of strain rate for stress states ranging from uniaxial to equi-biaxial tension.

  15. Effect of loading rate on fracture morphology in a high strength ductile steel

    OpenAIRE

    Venkert, A.; Guduru, P. R.; Ravichandran, G.

    2001-01-01

    Fracture experiments in a high-strength ductile steel (2.3Ni-1.3Cr-0.17C) were conducted under static and dynamic loading conditions in a three-point bend and a one-point bend configurations. A qualitative description of the influence of loading rate on the microscopic features of the fracture surfaces and their role in the fracture initiation process was considered. The fracture surfaces consist of tunneled region and shear lips. The size of the shear lips increases wit increasing loading ra...

  16. Consistent stress-strain ductile fracture model as applied to two grades of beryllium

    International Nuclear Information System (INIS)

    Priddy, T.G.; Benzley, S.E.; Ford, L.M.

    1980-01-01

    Published yield and ultimate biaxial stress and strain data for two grades of beryllium are correlated with a more complete method of characterizing macroscopic strain at fracture initiation in ductile materials. Results are compared with those obtained from an exponential, mean stress dependent, model. Simple statistical methods are employed to illustrate the degree of correlation for each method with the experimental data

  17. Fracture prediction in hydraulic bulging of AISI 304 austenitic steel sheets based on a modified ductile fracture criterion

    Science.gov (United States)

    Xu, Y.; Song, H. W.; Zhang, S. H.; Cheng, M.

    2011-08-01

    The demand for weight reduction in modern vehicle construction has resulted in an increase in the application of hydroforming processes for the manufacture of automotive lightweight components. This trend led to the research of evaluation on formability of the sheet or tube hydroforming to be noted, particularly the prediction of fracture. In this study, a new proposed approach based on damage theory for fracture prediction considering the deformation history was introduced. And the modified ductile fracture criterion was applied to predict the failure for hydraulic bulging of AISI 304 austenitic steel sheets. The material parameters in terms of the function of strain rate in the failure criterion were determined from the equivalent fracture strains corresponding tensile tests under different stress conditions. Then, in the finite element simulation the effect of strain rates and their distribution as well during practical sheet metal forming process was considered. The hydraulic bulging tests were carried out to identify the fracture behavior predicted from FE analysis. A comparison between the prediction and experimental results showed that the proposed approach with a modified ductile fracture criteria can give better fracture predictions than traditional ways.

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

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P. Prasad; Putatunda, Susil K

    2003-04-15

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-10-01

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

  20. Experimental and Computational Study of Ductile Fracture in Small Punch Tests

    Directory of Open Access Journals (Sweden)

    Betül Gülçimen Çakan

    2017-10-01

    Full Text Available A unified experimental-computational study on ductile fracture initiation and propagation during small punch testing is presented. Tests are carried out at room temperature with unnotched disks of different thicknesses where large-scale yielding prevails. In thinner specimens, the fracture occurs with severe necking under membrane tension, whereas for thicker ones a through thickness shearing mode prevails changing the crack orientation relative to the loading direction. Computational studies involve finite element simulations using a shear modified Gurson-Tvergaard-Needleman porous plasticity model with an integral-type nonlocal formulation. The predicted punch load-displacement curves and deformed profiles are in good agreement with the experimental results.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-12-31

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

  2. J-integral evaluation and stability analysis in the unstable ductile fracture

    International Nuclear Information System (INIS)

    Miyoshi, Toshiro; Yoshida, Yuichiro; Shiratori, Masaki.

    1984-01-01

    Concerning unstable ductile fracture, which is an important problem on the structural stability of line pipes, nuclear reactor piping and so on, the research on fracture mechanics parameters which control the beginning of the stable growth and unstable growth of cracks attracts interest. At present, as the parameters, the T-modulus based on J-integral crack tip opening angle, crack opening angle averaged over crack developing part, plastic work coefficient and so on have been proposed. The research on the effectiveness and inter-relation of these parameters is divided into generation phase and application phase, and by these researches, it was reported that all T-modulus, CTOA and COA took almost constant values in relation to crack development, except initial transition period. In order to decide which parameter is most appropriate, the detailed analysis is required. In this study, the analysis of unstable ductile fracture of a central crack test piece and a small tensile test piece was carried out by finite element method, and the evaluation of J-integral in relation to crack development, J-integral resistance value when COA is assumed to be a constant, the form of an unstable fracture occurring point and the compliance dependence were examined. The method of analysis, the evaluation of J-integral, J-integral resistance value, unstable fracture occurring point and stability diagram are described. (Kako, I.)

  3. Development of ductile cast iron for spent fuel cask applications using fracture mechanics principles

    International Nuclear Information System (INIS)

    Ray, K.K.; Tiwari, S.; Hemlata Kumari; Mamta Kumari; Kumar, Hemant; Albert, S.K.; Bhaduri, A.K.

    2016-01-01

    The structure-property relations of ductile cast irons (DCIs) with varying Cu content and ~1 wt.% Ni has been investigated with an emphasis on examining their fracture toughness property towards the development of suitable materials for large volume containers for transport of spent fuel. The detailed microstructural characteristics, hardness, tensile and fracture toughness properties of three DCIs were assessed in as-cast and annealed conditions. Fracture toughness values were determined using both ball indentation (K BI ) and J-integral (KJ Ic ) test. The obtained results assist to infer that: (i) the amount of pearlite and nodule count increases with increased amount of Cu, (ii) the hardness and strength values increases whereas fracture toughness values marginally decreases with increased Cu content, and (iii) the magnitudes of K BI estimated using a proposed analysis are in good agreement with KJ Ic values for the as-cast materials. (author)

  4. Technique for studies of ductile fracture in metals containing voids or inclusions

    International Nuclear Information System (INIS)

    Tittmann, B.R.; Nadler, H.; Paton, N.E.

    1976-01-01

    A technique of sample preparation is described for the study of the ductile fracture which occurs in metals containing failure initiating voids or inclusions. For the measurements discussed, commercial grade Ti--6 percent Al--4 percent V was machined into the form of right circular cylinders, each about 2 cm in dia and 3 cm long. The specimen was then prepared by taking a pair of these cylinders and diffusion bonding their end faces together to form one cylinder 6 cm long. Prior to bonding, the surfaces to be mated were machined in such a way then when mated, the desired shape, location, and number of defects would result arrayed on the bond plane. The results of the tensile tests show that of the three parameters measured, (yield stress, tensile strength, and ductility) only the ductility (reduction of area) exhibited a sufficiently significant variation over the samples tested to be a meaningful variable. The reason for the small change observed in ultimate strength with increasing volume fraction of defects is thought to be as follows: The metal near an array of voids may be compared with the necked portion of a tensile bar of ductile material. For this latter problem, Bridgman [Studies in Large Plastic Flow and Fracture, McGraw-Hill, New York, 1952] has shown that large triaxial stresses are induced in the necked region of a deformed bar. While the analogy is not exact, in many respects the region near a bond line containing voids is like the necked tensile bar. The bond-line voids may induce local triaxial stresses of the same type as those found for a cylindrically symmetric tensile bar, though the mathematical form and magnitude will be different. Consequently, while fracture originated at or near the bond-line voids at a strain below bulk-metal failure strain, the apparent failure stress is not markedly reduced even for significant volume fractions on bond-line voids

  5. A ductile fracture mechanics methodology for predicting pressure vessel and piping failure

    International Nuclear Information System (INIS)

    Landes, J.D.; Zhou, Z.

    1991-01-01

    This paper reports on a ductile fracture methodology based on one used more generally for the prediction of fracture behavior that was applied to the prediction of fracture behavior in pressure vessel and piping components. The model uses the load versus displacement record from a fracture toughness test to develop inputs for predicting the behavior of the structural component. The principle of load separation is used to convert the test record into two pieces of information, calibration functions which describe the structural deformation behavior and fracture toughness which describes the response of a crack-like flaw to the loading. These calibration functions and fracture toughness values which relate to the test specimen are then transformed to those appropriate to the structure. Often in this step computation procedures could be used but are not always necessary. The calibration functions and fracture for the structure are recombined to predict a load versus displacement behavior for the structure. The input for the model was generated from tests of compact specimen geometries; this geometry is often used for fracture toughness testing. The predictions were done for five model structures

  6. A new in situ technique for studying deformation and fracture in thin film ductile/brittle laminates

    International Nuclear Information System (INIS)

    Hackney, S.A.; Milligan, W.W.

    1991-01-01

    A new technique for studying deformation and fracture of thin film ductile/brittle laminates is described. The laminates are prepared by sputtering a brittle coating on top of an electropolished TEM thin foil. The composites are then strained in situ in the TEM. In this preliminary investigation, the composites consisted of a ductile aluminum substrate and a brittle silicon coating. Cracks in the brittle film grew discontinuously in bursts several micrometers in length. The crack opening displacement initiated plastic deformation in the ductile film, thus dissipating energy and allowing crack arrest. The interface was well bonded, and delamination was not observed. Due to the good interfacial bond and the crack opening behind the crack tip, it was possible to study very large plastic deformations and ductile fracture in the aluminum in situ, without buckling of the foil. The possibility of micromechanical modeling of the fracture behavior is briefly discussed. (orig.)

  7. Fracture mechanics aspects in the safe design of ductile iron shipping and storage containers

    International Nuclear Information System (INIS)

    Sappok, M.; Bounin, D.

    1996-01-01

    Containers made of ductile cast iron provide a safe method for transport of radioactive material. Contrary to widespread opinion ductile cast iron is a very tough material and can be manufactured in heavy sections. The containers are designed to withstand the very high impact loads of accidents like free drops onto unyielding targets. The design is based on postulated undetected crack-like flaws at the highest stressed location. Design must show that applied stress intensities are smaller than fracture toughness and no crack initiation and therefore also no crack propagation can occur. The design procedure followed in this paper is given in a new guideline still being drafted by the International Atomic Energy Agency

  8. Prevention of non-ductile fracture in 6061-T6 aluminum nuclear pressure vessels

    International Nuclear Information System (INIS)

    Yahr, G.T.

    1995-01-01

    The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Committee has approved rules for the use of 6061-T6 and 6061-T651 aluminum for the construction of Class 1 welded nuclear pressure vessels for temperatures not exceeding 149 C (300 F). Nuclear Code Case N-519 allows the use of this aluminum in the construction of low temperature research reactors such as the Advanced Neutron Source. The rules for protection against non-ductile fracture are discussed. The basis for a value of 25.3 MPa √m (23 ksi √in.) for the critical or reference stress intensity factor for use in the fracture analysis is presented. Requirements for consideration of the effects of neutron irradiation on the fracture toughness are discussed

  9. Evaluation of varying ductile fracture criteria for 42CrMo steel by compressions at different temperatures and strain rates.

    Science.gov (United States)

    Quan, Guo-zheng; Luo, Gui-chang; Mao, An; Liang, Jian-ting; Wu, Dong-sen

    2014-01-01

    Fracturing by ductile damage occurs quite naturally in metal forming processes, and ductile fracture of strain-softening alloy, here 42CrMo steel, cannot be evaluated through simple procedures such as tension testing. Under these circumstances, it is very significant and economical to find a way to evaluate the ductile fracture criteria (DFC) and identify the relationships between damage evolution and deformation conditions. Under the guidance of the Cockcroft-Latham fracture criteria, an innovative approach involving hot compression tests, numerical simulations, and mathematic computations provides mutual support to evaluate ductile damage cumulating process and DFC diagram along with deformation conditions, which has not been expounded by Cockcroft and Latham. The results show that the maximum damage value appears in the region of upsetting drum, while the minimal value appears in the middle region. Furthermore, DFC of 42CrMo steel at temperature range of 1123~1348 K and strain rate of 0.01~10 s(-1) are not constant but change in a range of 0.160~0.226; thus, they have been defined as varying ductile fracture criteria (VDFC) and characterized by a function of temperature and strain rate. In bulk forming operations, VDFC help technicians to choose suitable process parameters and avoid the occurrence of fracture.

  10. Evaluation of Varying Ductile Fracture Criteria for 42CrMo Steel by Compressions at Different Temperatures and Strain Rates

    Directory of Open Access Journals (Sweden)

    Guo-zheng Quan

    2014-01-01

    Full Text Available Fracturing by ductile damage occurs quite naturally in metal forming processes, and ductile fracture of strain-softening alloy, here 42CrMo steel, cannot be evaluated through simple procedures such as tension testing. Under these circumstances, it is very significant and economical to find a way to evaluate the ductile fracture criteria (DFC and identify the relationships between damage evolution and deformation conditions. Under the guidance of the Cockcroft-Latham fracture criteria, an innovative approach involving hot compression tests, numerical simulations, and mathematic computations provides mutual support to evaluate ductile damage cumulating process and DFC diagram along with deformation conditions, which has not been expounded by Cockcroft and Latham. The results show that the maximum damage value appears in the region of upsetting drum, while the minimal value appears in the middle region. Furthermore, DFC of 42CrMo steel at temperature range of 1123~1348 K and strain rate of 0.01~10 s-1 are not constant but change in a range of 0.160~0.226; thus, they have been defined as varying ductile fracture criteria (VDFC and characterized by a function of temperature and strain rate. In bulk forming operations, VDFC help technicians to choose suitable process parameters and avoid the occurrence of fracture.

  11. Evaluation of Varying Ductile Fracture Criteria for 42CrMo Steel by Compressions at Different Temperatures and Strain Rates

    Science.gov (United States)

    Quan, Guo-zheng; Luo, Gui-chang; Mao, An; Liang, Jian-ting; Wu, Dong-sen

    2014-01-01

    Fracturing by ductile damage occurs quite naturally in metal forming processes, and ductile fracture of strain-softening alloy, here 42CrMo steel, cannot be evaluated through simple procedures such as tension testing. Under these circumstances, it is very significant and economical to find a way to evaluate the ductile fracture criteria (DFC) and identify the relationships between damage evolution and deformation conditions. Under the guidance of the Cockcroft-Latham fracture criteria, an innovative approach involving hot compression tests, numerical simulations, and mathematic computations provides mutual support to evaluate ductile damage cumulating process and DFC diagram along with deformation conditions, which has not been expounded by Cockcroft and Latham. The results show that the maximum damage value appears in the region of upsetting drum, while the minimal value appears in the middle region. Furthermore, DFC of 42CrMo steel at temperature range of 1123~1348 K and strain rate of 0.01~10 s−1 are not constant but change in a range of 0.160~0.226; thus, they have been defined as varying ductile fracture criteria (VDFC) and characterized by a function of temperature and strain rate. In bulk forming operations, VDFC help technicians to choose suitable process parameters and avoid the occurrence of fracture. PMID:24592175

  12. Assessment of Ductile, Brittle, and Fatigue Fractures of Metals Using Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Gheorghe Hutiu

    2018-02-01

    Full Text Available Some forensic in situ investigations, such as those needed in transportation (for aviation, maritime, road, or rail accidents or for parts working under harsh conditions (e.g., pipes or turbines would benefit from a method/technique that distinguishes ductile from brittle fractures of metals—as material defects are one of the potential causes of incidents. Nowadays, the gold standard in material studies is represented by scanning electron microscopy (SEM. However, SEM instruments are large, expensive, time-consuming, and lab-based; hence, in situ measurements are impossible. To tackle these issues, we propose as an alternative, lower-cost, sufficiently high-resolution technique, Optical Coherence Tomography (OCT to perform fracture analysis by obtaining the topography of metallic surfaces. Several metals have been considered in this study: low soft carbon steels, lamellar graphite cast iron, an antifriction alloy, high-quality rolled steel, stainless steel, and ductile cast iron. An in-house developed Swept Source (SS OCT system, Master-Slave (MS enhanced is used, and height profiles of the samples’ surfaces were generated. Two configurations were used: one where the dimension of the voxel was 1000 μm3 and a second one of 160 μm3—with a 10 μm and a 4 μm transversal resolution, respectively. These height profiles allowed for concluding that the carbon steel samples were subject to ductile fracture, while the cast iron and antifriction alloy samples were subjected to brittle fracture. The validation of OCT images has been made with SEM images obtained with a 4 nm resolution. Although the OCT images are of a much lower resolution than the SEM ones, we demonstrate that they are sufficiently good to obtain clear images of the grains of the metallic materials and thus to distinguish between ductile and brittle fractures—especially with the higher resolution MS/SS-OCT system. The investigation is finally extended to the most useful case of

  13. Strategy for characterizing fracture toughness in the ductile to brittle transition regime

    International Nuclear Information System (INIS)

    Heerens, J.; Zerbst, U.; Schwalbe, K.H.

    1993-01-01

    A tentative method is proposed for treating the scatter and size effects of fracture toughness of ferritic steels in the ductile-to-brittle transition regime. The method is aimed at the determination of the probability function for initiation of fast growing cleavage cracks under the plane strain condition. The practical relevance of this method has been checked with toughness data sets obtained from various CT-specimen sizes and CCT-specimens of a pressure vessel tested at two different temperatures in the transition regime. (orig.)

  14. Size effect on brittle and ductile fracture of two-dimensional interlinked carbon nanotube network

    Science.gov (United States)

    Jing, Yuhang; Aluru, N. R.

    2017-09-01

    The mechanical properties of two-dimensional (2D) interlinked carbon nanotube (CNT) network are investigated using ab initio calculation and molecular dynamics simulations (MD) with Reaxff force field. The simulation results show that bulk 2D interlinked CNT network has good mechanical properties along the axial direction which can be comparable to that of single-walled CNT and graphene, but has better ductility along the radial direction than single-walled CNT and graphene. In addition, the mechanical properties of 2D interlinked CNT network ribbon along the radial direction depend strongly on the size of the ribbon. The Young's modulus and Poisson's ratio decrease as the size increases while the fracture strain increases with the size increasing. By analyzing the atomic structural (both bond length and atomic von Mises stress) evolution of the ribbons, the mechanism of a brittle-to-ductile transition is revealed. The exploration of the mechanical properties of the 2D interlinked CNT network paves the way for application of the relevant devices that can benefit from the high Young's modulus, high tensile strength, and good ductility.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-12-01

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

  16. Algorithm to measure automatically the ductile/brittle fracture of Charpy test specimens

    Science.gov (United States)

    Camargo, Anyela; Tickle, Andrew J.; Smith, Jeremy S.

    2010-04-01

    The Charpy impact test technique assesses the toughness of an engineering material. The test measures the amount of energy a specimen can resist before it is broken by the impact of a heavy pendulum. Estimation of toughness is carried out manually by a skilled operator; they assess the percentage of light-reflective brittle regions on the fracture area. Because this assessment is performed manually, there is some subjectivity in the results. This study proposes a machine-based-learning algorithm to estimate this measure automatically. The method consists of capturing a digital image of the fracture surface after impact, preprocessing it, dividing it up into 10×10 pixel segments, and extracting from each segment features associated with its texture. Feature vectors feed a classifier whose purpose is to distinguish between brittle and ductile images (binary output). To estimate toughness, the classifier's outputs are used to construct a binary image, which is postprocessed to determine the percentage of the brittle region. To assess the accuracy of the algorithm, automatically and manually classified images are compared. Results show that the algorithm proposed was able to distinguish between brittle and ductile regions successfully and could be used instead of the manually performed technique.

  17. Phase-field modelling of ductile fracture: a variational gradient-extended plasticity-damage theory and its micromorphic regularization.

    Science.gov (United States)

    Miehe, C; Teichtmeister, S; Aldakheel, F

    2016-04-28

    This work outlines a novel variational-based theory for the phase-field modelling of ductile fracture in elastic-plastic solids undergoing large strains. The phase-field approach regularizes sharp crack surfaces within a pure continuum setting by a specific gradient damage modelling. It is linked to a formulation of gradient plasticity at finite strains. The framework includes two independent length scales which regularize both the plastic response as well as the crack discontinuities. This ensures that the damage zones of ductile fracture are inside of plastic zones, and guarantees on the computational side a mesh objectivity in post-critical ranges. © 2016 The Author(s).

  18. Interpreting Fracture Patterns in Sandstones Interbedded with Ductile Strata at the Salt Valley Anticline, Arches National Park, Utah; TOPICAL

    International Nuclear Information System (INIS)

    LORENZ, JOHN C.; COOPER, SCOTT P.

    2001-01-01

    Sandstones that overlie or that are interbedded with evaporitic or other ductile strata commonly contain numerous localized domains of fractures, each covering an area of a few square miles. Fractures within the Entrada Sandstone at the Salt Valley Anticline are associated with salt mobility within the underlying Paradox Formation. The fracture relationships observed at Salt Valley (along with examples from Paleozoic strata at the southern edge of the Holbrook basin in northeastern Arizona, and sandstones of the Frontier Formation along the western edge of the Green River basin in southwestern Wyoming), show that although each fracture domain may contain consistently oriented fractures, the orientations and patterns of the fractures vary considerably from domain to domain. Most of the fracture patterns in the brittle sandstones are related to local stresses created by subtle, irregular flexures resulting from mobility of the associated, interbedded ductile strata (halite or shale). Sequential episodes of evaporite dissolution and/or mobility in different directions can result in multiple, superimposed fracture sets in the associated sandstones. Multiple sets of superimposed fractures create reservoir-quality fracture interconnectivity within restricted localities of a formation. However, it is difficult to predict the orientations and characteristics of this type of fracturing in the subsurface. This is primarily because the orientations and characteristics of these fractures typically have little relationship to the regional tectonic stresses that might be used to predict fracture characteristics prior to drilling. Nevertheless, the high probability of numerous, intersecting fractures in such settings attests to the importance of determining fracture orientations in these types of fractured reservoirs

  19. Modeling the Ductile Brittle Fracture Transition in Reactor Pressure Vessel Steels using a Cohesive Zone Model based approach

    Energy Technology Data Exchange (ETDEWEB)

    Pritam Chakraborty; S. Bulent Biner

    2013-10-01

    Fracture properties of Reactor Pressure Vessel (RPV) steels show large variations with changes in temperature and irradiation levels. Brittle behavior is observed at lower temperatures and/or higher irradiation levels whereas ductile mode of failure is predominant at higher temperatures and/or lower irradiation levels. In addition to such temperature and radiation dependent fracture behavior, significant scatter in fracture toughness has also been observed. As a consequence of such variability in fracture behavior, accurate estimates of fracture properties of RPV steels are of utmost importance for safe and reliable operation of reactor pressure vessels. A cohesive zone based approach is being pursued in the present study where an attempt is made to obtain a unified law capturing both stable crack growth (ductile fracture) and unstable failure (cleavage fracture). The parameters of the constitutive model are dependent on both temperature and failure probability. The effect of irradiation has not been considered in the present study. The use of such a cohesive zone based approach would allow the modeling of explicit crack growth at both stable and unstable regimes of fracture. Also it would provide the possibility to incorporate more physical lower length scale models to predict DBT. Such a multi-scale approach would significantly improve the predictive capabilities of the model, which is still largely empirical.

  20. Modelling the ductile brittle fracture transition in reactor pressure vessel steels using a cohesive zone model based approach

    International Nuclear Information System (INIS)

    Chakraborty, Pritam; Bulent Biner, S.

    2015-01-01

    Fracture properties of Reactor Pressure Vessel (RPV) steels show large variations with changes in temperature and irradiation levels. Brittle behaviour is observed at lower temperatures and/or higher irradiation levels whereas ductile mode of failure is predominant at higher temperatures and/or lower irradiation levels. In addition to such temperature and radiation dependent fracture behaviour, significant scatter in fracture toughness has also been observed. As a consequence of such variability in fracture behaviour, accurate estimates of fracture properties of RPV steels are of utmost importance for safe and reliable operation of reactor pressure vessels. A cohesive zone based approach is being pursued in the present study where an attempt is made to obtain a unified law capturing both stable crack growth (ductile fracture) and unstable failure (cleavage fracture). The parameters of the constitutive model are dependent on both temperature and failure probability. The effect of irradiation has not been considered in the present study. The use of such a cohesive zone based approach would allow the modelling of explicit crack growth at both stable and unstable regimes of fracture. Also it would provide the possibility to incorporate more physical lower length scale models to predict DBT. Such a multi-scale approach would significantly improve the predictive capabilities of the model, which is still largely empirical. (authors)

  1. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part I. Ductility and fracture toughness

    Energy Technology Data Exchange (ETDEWEB)

    Margolin, B., E-mail: mail@crism.ru; Sorokin, A.; Shvetsova, V.; Minkin, A.; Potapova, V.; Smirnov, V.

    2016-11-15

    The radiation swelling effect on the fracture properties of irradiated austenitic steels under static loading has been studied and analyzed from the mechanical and physical viewpoints. Experimental data on the stress-strain curves, fracture strain, fracture toughness and fracture mechanisms have been represented for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various swelling. Some phenomena in mechanical behaviour of irradiated austenitic steels have been revealed and explained as follows: a sharp decrease of fracture toughness with swelling growth; untypical large increase of fracture toughness with decrease of the test temperature; some increase of fracture toughness after preliminary cyclic loading. Role of channel deformation and channel fracture has been clarified in the properties of irradiated austenitic steel and different tendencies to channel deformation have been shown and explained for the same austenitic steel irradiated at different temperatures and neutron doses.

  2. Influence of material ductility and crack surface roughness on fracture instability

    International Nuclear Information System (INIS)

    Khezrzadeh, Hamed; Wnuk, Michael P; Yavari, Arash

    2011-01-01

    This paper presents a stability analysis for fractal cracks. First, the Westergaard stress functions are proposed for semi-infinite and finite smooth cracks embedded in the stress fields associated with the corresponding self-affine fractal cracks. These new stress functions satisfy all the required boundary conditions and according to Wnuk and Yavari's (2003 Eng. Fract. Mech. 70 1659-74) embedded crack model they are used to derive the stress and displacement fields generated around a fractal crack. These results are then used in conjunction with the final stretch criterion to study the quasi-static stable crack extension, which in ductile materials precedes the global failure. The material resistance curves are determined by solving certain nonlinear differential equations and then employed in predicting the stress levels at the onset of stable crack growth and at the critical point, where a transition to the catastrophic failure occurs. It is shown that the incorporation of the fractal geometry into the crack model, i.e. accounting for the roughness of the crack surfaces, results in (1) higher threshold levels of the material resistance to crack propagation and (2) higher levels of the critical stresses associated with the onset of catastrophic fracture. While the process of quasi-static stable crack growth (SCG) is viewed as a sequence of local instability states, the terminal instability attained at the end of this process is identified with the global instability. The phenomenon of SCG can be used as an early warning sign in fracture detection and prevention.

  3. Study on the formation of micro-voids during ductile fracture

    Science.gov (United States)

    Long, Shao-Lei; Liang, Yi-Long; Lu, Ye-Mao; Yang, Ming; Yin, Cun-Hong

    2018-01-01

    In this work, the formation of micro-voids for ductile fracture has been discussed with regards to the classical nucleation theory from the phase transformation in 20CrNi2Mo steel. The differences in them were determined based upon the driving force and the resistance. In terms of tensile load, the driving force was the energy of tensile load before necking, while the resistance was the surface energy from the formation of mass of micro-voids, as determined by the fracture toughness instead of the phase transformation. Finally, the relationship between the formation of micro-voids and the macroscopic properties was discussed. The results illustrated that the formation of micro-voids depended on the elastic-plastic energy and on the yield strength represented by r* (the critical formation radius) and {{Δ }}{G}* (the critical formation energy). These results were confirmed from r 1* (with the experiment) and r 2* (with the calculation). The work provided a novel way to study the relationship of micro-parameters and macro-properties. In addition, it was found that the critical formation diameter (2r*) of micro-voids was close to the width of martensite lath (d l).

  4. Ductile fracture toughness of modified A 302 Grade B Plate materials, data analysis. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    McCabe, D.E.; Manneschmidt, E.T.; Swain, R.L.

    1997-01-01

    The goal of this work was to develop ductile fracture toughness data in the form of J-R curves for modified A302 grade B plate materials typical of those used in reactor pressure vessels. A previous experimental study on one heat of A302 grade B plate showed decreasing J-R curves with increased specimen thickness. This characteristic has not been observed in tests made on recent production materials of A533 grade B and A508 class 2 pressure vessel steels. It was unknown if the departure from norm for the material was a generic characteristic for all heats of A302 grade B steels or unique to that particular plate. Seven heats of modified A302 grade B steel and one heat of vintage A533 grade B steel were tested for chemical content, tensile properties, Charpy transition temperature curves, drop-weight nil-ductility transition (NDT) temperature, and J-R curves. Tensile tests were made in the three principal orientations and at four temperatures, ranging from room temperature to 550F. Charpy V-notch transition temperature curves were obtained in longitudinal, transverse, and short transverse orientations. J-R curves were made using four specimen sizes (1/2T, 1T, 2T, and 4T). The fracture mechanics-based evaluation method covered three test orientations and three test temperatures (80, 400, and 550F). However, the coverage of these variables was contingent upon the amount of material provided. Drop-weight NDT temperature was determined for the T-L orientation only. None of the heats of modified A302 grade B showed size effects of any consequence on the J-R curve behavior. Crack orientation effects were present, but none were severe enough to be reported as atypical. A test temperature increase from 180 to 550F produced the usual loss in J-R curve fracture toughness. Generic J-R curves and curve fits were generated to represent each heat of material. This volume deals with the evaluation of data and the discussion of technical findings. 8 refs., 18 figs., 8 tabs.

  5. Ductile fracture toughness of modified A 302 Grade B Plate materials, data analysis. Volume 1

    International Nuclear Information System (INIS)

    McCabe, D.E.; Manneschmidt, E.T.; Swain, R.L.

    1997-01-01

    The goal of this work was to develop ductile fracture toughness data in the form of J-R curves for modified A302 grade B plate materials typical of those used in reactor pressure vessels. A previous experimental study on one heat of A302 grade B plate showed decreasing J-R curves with increased specimen thickness. This characteristic has not been observed in tests made on recent production materials of A533 grade B and A508 class 2 pressure vessel steels. It was unknown if the departure from norm for the material was a generic characteristic for all heats of A302 grade B steels or unique to that particular plate. Seven heats of modified A302 grade B steel and one heat of vintage A533 grade B steel were tested for chemical content, tensile properties, Charpy transition temperature curves, drop-weight nil-ductility transition (NDT) temperature, and J-R curves. Tensile tests were made in the three principal orientations and at four temperatures, ranging from room temperature to 550F. Charpy V-notch transition temperature curves were obtained in longitudinal, transverse, and short transverse orientations. J-R curves were made using four specimen sizes (1/2T, 1T, 2T, and 4T). The fracture mechanics-based evaluation method covered three test orientations and three test temperatures (80, 400, and 550F). However, the coverage of these variables was contingent upon the amount of material provided. Drop-weight NDT temperature was determined for the T-L orientation only. None of the heats of modified A302 grade B showed size effects of any consequence on the J-R curve behavior. Crack orientation effects were present, but none were severe enough to be reported as atypical. A test temperature increase from 180 to 550F produced the usual loss in J-R curve fracture toughness. Generic J-R curves and curve fits were generated to represent each heat of material. This volume deals with the evaluation of data and the discussion of technical findings. 8 refs., 18 figs., 8 tabs

  6. Ductile fracture toughness of modified A 302 grade B plate materials. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    McCabe, D.E.; Manneschmidt, E.T.; Swain, R.L.

    1997-02-01

    The objective of this work was to develop ductile fracture toughness data in the form of J-R curves for modified A 302 grade B plate materials typical of those used in fabricating reactor pressure vessels. A previous experimental study at Materials Engineering Associates (MEA) on one particular heat of A 302 grade B plate showed decreasing J-R curves with increased specimen thickness. This characteristic has not been observed in numerous tests made on the more recent production materials of A 533 grade B and A 508 class 2 pressure vessel steels. It was unknown if the departure from norm for the MEA material was a generic characteristic for all heats of A 302 grade B steels or just unique to that one particular plate. Seven heats of modified A 302 grade B steel and one heat of vintage A 533 grade B steel were provided to this project by the General Electric Company of San Jose, California. All plates were tested for chemical content, tensile properties, Charpy transition temperature curves, drop-weight nil-ductility transition (NDT) temperature, and J-R curves. Tensile tests were made in the three principal orientations and at four temperatures, ranging from room temperature to 550{degrees}F (288{degrees}C). Charpy V-notch transition temperature curves were obtained in longitudinal, transverse, and short transverse orientations. J-R curves were made using four specimen sizes (1/2T, IT, 2T, and 4T). None of the seven heats of modified A 302 grade showed size effects of any consequence on the J-R curve behavior. Crack orientation effects were present, but none were severe enough to be reported as atypical. A test temperature increase from 180 to 550{degrees}F (82 to 288{degrees}C) produced the usual loss in J-R curve fracture toughness. Generic J-R curves and mathematical curve fits to the same were generated to represent each heat of material. This volume is a compilation of all data developed.

  7. Ductile fracture toughness of modified A 302 grade B plate materials. Volume 2

    International Nuclear Information System (INIS)

    McCabe, D.E.; Manneschmidt, E.T.; Swain, R.L.

    1997-02-01

    The objective of this work was to develop ductile fracture toughness data in the form of J-R curves for modified A 302 grade B plate materials typical of those used in fabricating reactor pressure vessels. A previous experimental study at Materials Engineering Associates (MEA) on one particular heat of A 302 grade B plate showed decreasing J-R curves with increased specimen thickness. This characteristic has not been observed in numerous tests made on the more recent production materials of A 533 grade B and A 508 class 2 pressure vessel steels. It was unknown if the departure from norm for the MEA material was a generic characteristic for all heats of A 302 grade B steels or just unique to that one particular plate. Seven heats of modified A 302 grade B steel and one heat of vintage A 533 grade B steel were provided to this project by the General Electric Company of San Jose, California. All plates were tested for chemical content, tensile properties, Charpy transition temperature curves, drop-weight nil-ductility transition (NDT) temperature, and J-R curves. Tensile tests were made in the three principal orientations and at four temperatures, ranging from room temperature to 550 degrees F (288 degrees C). Charpy V-notch transition temperature curves were obtained in longitudinal, transverse, and short transverse orientations. J-R curves were made using four specimen sizes (1/2T, IT, 2T, and 4T). None of the seven heats of modified A 302 grade showed size effects of any consequence on the J-R curve behavior. Crack orientation effects were present, but none were severe enough to be reported as atypical. A test temperature increase from 180 to 550 degrees F (82 to 288 degrees C) produced the usual loss in J-R curve fracture toughness. Generic J-R curves and mathematical curve fits to the same were generated to represent each heat of material. This volume is a compilation of all data developed

  8. On the prediction of ductile fracture by void coalescence and strain localization

    Science.gov (United States)

    Luo, Tuo; Gao, Xiaosheng

    2018-04-01

    This paper presents a unit cell model based on the observation that ductile fracture occurs when plastic flow is localized in a band. The unit cell consists of three void containing material units stacked in the direction normal to the localization plane. Localization takes place in the middle material unit while the two outer units undergo elastic recovery after failure occurs. Thus a failure criterion is established as when the macroscopic effective strain of the outer material units reaches the maximum value. Analyses are conducted to demonstrate the effect of the voids existing outside the localization band. Comparisons of the present model with several previous models suggest that the present model is not only easy to implement in finite element analysis but also more suitable to robustly determine the failure strain. A series of unit cell analyses are conducted for various macroscopic stress triaxialities and Lode parameters. The analysis results confirm that for a fixed Lode parameter, the failure strain decreases exponentially with the stress triaxiality and for a given stress triaxiality, it increases as the stress state approaches the generalized tension and generalized compression. The analysis results also reveal the effect of the stress state on the deformed void shape within and near the localization band.

  9. ``Global and local approaches of fracture in the ductile to brittle regime of a low alloy steel``; ``Approches globale et locale de la rupture dans le domaine de transition fragile-ductile d`un acier faiblement allie``

    Energy Technology Data Exchange (ETDEWEB)

    Renevey, S

    1998-12-31

    The study is a contribution to the prediction of flow fracture toughness of low alloy steel and to a better knowledge of fracture behavior in the ductile to brittle transition region. Experiments were performed on a nozzle cut-off from a pressurized water reactor vessel made of steels A508C13 type steel. Axisymmetrical notched specimens were tested to study the fracture onset in a volume element while pre-cracked specimens were used to investigate cleavage fracture after stable crack growth. Systematic observations of fracture surfaces showed manganese sulfide inclusions (MnS) at cleavage sites or in the vicinity. The experimental results were used for modelling by the local approach to fracture. In a volume element the fracture is described by an original probabilistic model. This model is based on volume fraction distributions of MnS inclusions gathered in clusters and on the assumption of a competition without interaction between ductile and cleavage fracture modes. This model was applied to pre-cracked specimens (CT specimens). It is able to describe the scatter in the toughness after a small stable crack growth if a temperature effect on the cleavage stress is assumed. So, the modelling is able to give a lower bound of fracture toughness as a function of temperature. (author) 100 refs.

  10. An experimental and analytical study of ductile fracture and stable crack-growth

    International Nuclear Information System (INIS)

    Rousselier, G.

    1978-01-01

    A study is described, the objectives of which were to define a numerical model for stable crack growth, to calibrate the model by tensile tests, and to obtain agreement between corresponding numerical calculations and experiments on cracked specimens. The model was based on a finite element program with a critical state at the crack tip defined by a ductility curve: equivalent plastic strain versus stress triaxiality. The curve was determined by tests on notched tensile specimens of a low alloy rotor steel. The critical states corresponded to the initiation of a crack at the centre of the specimens. Three point bend tests were also performed and experimental and numerical load displacement curves and crack growth versus displacement curves were compared. Agreement with experiments on cracked specimens was obtained by simple fittings of the 'ductility' curve in the high triaxiality area. Results are discussed and it is indicated where future progress might be made in numerical modelling of cracked bodies. (author)

  11. Application of micromechanical models of ductile fracture initiation to reactor pressure vessel materials

    International Nuclear Information System (INIS)

    Chaouadi, R.; Walle, E. van; Fabry, A.; Velde, J. van de; Meester, P. de

    1996-01-01

    The aim of the current study is the application of local micromechanical models to predict crack initiation in ductile materials. Two reactor pressure vessel materials have been selected for this study: JRQ IAEA monitor base metal (A533B Cl.1) and Doel-IV weld material. Charpy impact tests have been performed in both un-irradiated and irradiated conditions. In addition to standard tensile tests, notched tensile specimens have been tested. The upper shelf energy of the weld material remains almost un-affected by irradiation, whereas a decrease of 20% is detected for the base metal. Accordingly, the tensile properties of the weld material do not reveal a clear irradiation effect on the yield and ultimate stresses, this in contrast to the base material flow properties. The tensile tests have been analyzed in terms of micromechanical models. A good correlation is found between the standard tests and the micromechanical models, that are able to predict the ductile damage evolution in these materials. Additional information on the ductility behavior of these materials is revealed by this micromechanical analysis

  12. Ductile fracture mechanism of low-temperature In-48Sn alloy joint under high strain rate loading.

    Science.gov (United States)

    Kim, Jong-Woong; Jung, Seung-Boo

    2012-04-01

    The failure behaviors of In-48Sn solder ball joints under various strain rate loadings were investigated with both experimental and finite element modeling study. The bonding force of In-48Sn solder on an Ni plated Cu pad increased with increasing shear speed, mainly due to the high strain-rate sensitivity of the solder alloy. In contrast to the cases of Sn-based Pb-free solder joints, the transition of the fracture mode from a ductile mode to a brittle mode was not observed in this solder joint system due to the soft nature of the In-48Sn alloy. This result is discussed in terms of the relationship between the strain-rate of the solder alloy, the work-hardening effect and the resulting stress concentration at the interfacial regions.

  13. Correlation of nodular austempered ductile iron (ADI) microstructural parameters and fatigue properties using an approach based on fracture mechanics

    International Nuclear Information System (INIS)

    Dias, Jose Felipe; Fonseca, Vinicius Rizzuti; Godefroid, Leonardo Barbosa; Ribeiro, Gabriel de Oliveira

    2010-01-01

    An investigation has been accomplished to check the effect of temperature and austempering time on austempered ductile iron (ADI) properties by means of fracture toughness (K C ) and fatigue threshold (∆K th ) tests. The correlation of ADI microstructural parameters and ADI two mechanical parameters: KC and Kth, is evaluated. Three sets of samples have ben extracted from ADI casting Y blocks produced in industrial conditions.and austenitized at 900°C for 1.5 hour. The austempering process has been performed in the following ways: the first set was austenitized at 300 deg C for 4 hours, the second set at 360°C for 1.5 hour and the third at 360°C for 0.6 hour. These distinct austempering processes have been adopted in order to obtain distinct microstructures containing austenite with two different carbon rates and two ferritic cell sizes. The materials have been characterized by means of optical and electronic microscopy, X-ray diffraction and mechanical tests. All materials have presented equivalent fatigue crack propagation rates, fracture toughness in the range between 94 and 128 MPa·m 1/2 and ∆K th in the range between 5,7 and 6,4 MPa·m 1/2 . The experimental results have confirmed the effect of microstructural properties (austenitic volumetric rate, austenitic carbon rate, ferritic cell size, total matrix carbon content) on fracture toughness (K C ) and fatigue threshold (∆K th ). Further, it was found that following parameters: fracture toughness (K C ), fatigue threshold ((∆K th ) and impact strength are correlated with the total matrix carbon content and ferritic cell size. (author)

  14. Analysis of the competition between brittle and ductile fracture: application for the mechanical behaviour of C-Mn and theirs welds

    International Nuclear Information System (INIS)

    Le Corre, V.

    2006-09-01

    This study deals with the fracture behaviour of welded thin structures in the ductile to brittle transition range. It aims to propose a criterion to define the conditions for which the risk of fracture by cleavage does not exist on a cracked structure. The literature review shows that the difficulties of prediction of the fracture behaviour of a structure are related to the dependence of the fracture probability to the mechanical fields at the crack tip. The ductile to brittle transition range thus depends on the studied geometry of the structure. A threshold stress, below which cleavage cannot take place, is defined using fracture tests on notched specimens broken at very low temperature. The finite element numerical simulation of fracture tests on CT specimens in the transition range shows a linear relationship between the fracture probability and the volume exceeding the threshold stress, thus showing the relevance of the proposed criterion. Moreover, several relations are established allowing to simplify the identification of the criterion parameters. The criterion is applied to a nuclear structural C-Mn steel, by focusing more particularly on the higher boundary of the transition range. A fracture test on a full-scale pipe is designed, developed, carried out and analysed using its numerical simulation. The results show firstly that, on the structure, the transition range is shifted in temperature, compared to laboratory specimens, due to the low plasticity constraint achieved in thin structures, and secondly that the threshold stress criterion allows to estimate simply this shift. (author)

  15. Ductile fracture behavior of 6-inch diameter type 304 stainless steel and STS 42 carbon steel piping containing a through-wall or part-through crack

    International Nuclear Information System (INIS)

    Shibata, Katsuyuki; Ohba, Toshihiro; Kawamura, Takaichi; Miyazono, Shohachiro; Kaneko, Tadashi; Yokoyama, Norio.

    1986-05-01

    The double ended guillotine break philosophy in the design base accident of the nuclear power plant is considered to be overly conservative from the view point of piping design. Through the past experiences and developments of the fabrication, inspection, and operation of nuclear power plants, it has been recognized that the Leak-Before-Break (LBB) concept can be justified in the LWR pressure boundary pipings. In order to verify the LBB concept, extensive experimental and theoretical works are being conducted in many countries. Furthermore, a revised piping design standard, in which LBB concept is introduced, is under preparation in Japan, U.S.A., and European countries. At JAERI, a research program to investigate the unstable ductile fracture behavior of LWR piping under bending load has been carried out as a part of the LBB verification researches since 1983. This report summarizes the result of the ductile fracture tests conducted at room temperature in 1983 and 84. The 6-inch diameter pipes of type 304 stainless steel and STS 42 carbon steel pipe with a through-wall or part-through crack were tested under bending load with low or high compliance condition at room temperature. Pipe fracture data were obtained from the test as regards to load- displacement curve, crack extension, net section stress, J-resistance curve, and so on. Besides, the influence of the compliance on the fracture behavior was examined. Discussions are performed on the ductile pipe fracture criterion, flaw evaluation criterion, and LBB evaluation method. (author)

  16. Determination of the fracture thoughness curve within the ductile brittle transition region in ferritic steel AISI4140

    International Nuclear Information System (INIS)

    Hernandez, R.; Orozco, E.

    1996-01-01

    The aim of this work is to show the validity in the employment of small test tubes (1/2 T) in order to determine the fracture thoughness in ferritic steels that experience the beginning of cracking by cleavage, to elastic instability, and/or elasto-plastic. It was calculated the change of fracture thoughness in the ductile brittle transition region like function of the temperature employing statistic methods for steel to the annealed carbon of the type AISI4140. The testings were carried out within an interval of temperatures, where the cracking by cleavage and/or pop-in occurs. The thoughness curve of the cracking in the transition region was determined, in small test tubes 1/2 T, and in standard test tubes, 1T. It was calculated the beginning of instability of the integral J, J IC , and was converted to its equivalent in K JC units based in the ASTM Standard rev. 6-12-95 (ref. 6). (Author)

  17. The application of ductile-fracture analysis to predictions of pressure-tube failure

    International Nuclear Information System (INIS)

    Simpson, L.A.

    1981-08-01

    Progress during the past six years towards establishing a method for predicting critical crack length in a reactor pressure tube, based on data from tests on small fracture-mechanics specimens, is reviewed. The disadvantages of relying on data from burst tests alone are described along with the benefits of a small-specimen method. It is clear from the work reviewed that only an approach that can account for the ability of the presssure tube material to increase its crack-growth resistance during stable crack extension is suitable for the prediction of critical crack length. A method that utilizes crack-growth resistance curves based on crack-opening displacement, or the J integral, is described, along with a large body of experimental data. It is concluded that the resistance curve approach provides a viable method for the analysis of fracture in pressure tubes that can greatly improve our understanding of the material's behaviour

  18. Studies on ductile unstable fracture of piping materials in light water reactors, (2)

    International Nuclear Information System (INIS)

    Yasuda, Yuji; Shibata, Katsuyuki; Ohba, Toshihiro; Kawamura, Takaichi; Onizawa, Kunio; Miyazono, Shohachiro

    1986-07-01

    A pipe fracture test program has been conducted in Japan Atomic Energy Research Institute (JAERI) using austenitic stainless steel pipes and carbon steel pipes to investigate fracture behavior of the cracked pipe and to demonstrate the validity of the ''Leak Before Break'' concept for nuclear pressure boundary piping. This report describes the results of the laboratory-scale tests on center-cracked-tension (CCT) specimens machined from the 12-inch diameter Type 304 Nuclear Grade stainless steel pipe under tensile loading condition at room temperature. The program approach includes two efforts. The first phase develops J-R curve data for CCT specimens to characterize crack growth resistance. Furthermore, the flow stress obtained from these tests was applied to predict the collapse load of stainless steel pipe with a through-wall circumferential crack, based on the net-section collapse criterion. In the second phase of this program, unstable fracture experiments were conducted using compliant disc spring device. J-based tearing instability criterion was compared with the test results, and the validity of this criterion was discussed. (author)

  19. Effect of the martensite distribution on the strain hardening and ductile fracture behaviors in dual-phase steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Kyosun, E-mail: paku08@zaiko.kyushu-u.ac.jp [Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Nishiyama, Masato, E-mail: nishiyama11@zaiko.kyushu-u.ac.jp [Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Nakada, Nobuo, E-mail: nakada@zaiko.kyushu-u.ac.jp [Department of Materials Science and Engineering, Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Tsuchiyama, Toshihiro, E-mail: toshi@zaiko.kyushu-u.ac.jp [Department of Materials Science and Engineering, Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Takaki, Setsuo, E-mail: takaki@zaiko.kyushu-u.ac.jp [Department of Materials Science and Engineering, Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan)

    2014-05-01

    In order to clarify the effects of the martensite distribution on the mechanical properties of low-carbon dual-phase steel, four types of dual-phase steel with different ferrite grain sizes and martensite distributions were prepared using a thermomechanical treatment. The tensile properties of these steels were investigated; in particular, the strain hardening and the ductile fracture behaviors were discussed in terms of the strain partitioning between the ferrite and martensite and the formation and growth of micro-voids, respectively. When the martensite grains surround the ferrite grains and form a chain-like networked structure, the strain hardenability is greatly improved without a significant loss of elongation, while the necking deformability is considerably reduced. A digital-image correlation analysis revealed that the tensile strain in the martensite region in the chain-like networked dual-phase structure is markedly increased during tensile deformation, which leads to an improvement in the strain hardenability. On the other hand, the joint part of the martensite grains in the structure acts as a preferential formation site for micro-voids. The number density of the micro-voids rapidly increases with increasing tensile strain, which would cause the lower necking deformability.

  20. Application of stable crack growth in fracture assessment of defects in ductile materials

    International Nuclear Information System (INIS)

    Dillstroem, Peter

    2009-06-01

    This report goes through the use of methods/standards, which consider stable (J-controlled) crack growth. We have demonstrated the following: - ASME XI, App. C, App. H, which deals with analysis of stainless steel and ferritic piping, take account of stable growth. In App. C, this corresponds to the inclusion of stable growth up to Δa ∼ 10 mm. - R6-method, BS 7910:1999 and ASME XI, Code Case N-494, contains an established formalism to take account of stable growth. A prerequisite is that you have access to relevant and authentic material data in the form of fracture resistance K k /J k and J r curves. - All of the above methods/standards are applicable in the nuclear context. We reported also that required to produce relevant and valid data (fracture resistance K k /J k and J r curves) to be used for the analysis of stable growth. This report does not specify how much stable crack that can be counted at a Safety Assessment

  1. Research of a fracture criterion for ductile metals. Application to austenitic stainless steels

    International Nuclear Information System (INIS)

    Chavaillard, J.P.

    1984-01-01

    Elasto-plastic Fracture Mechanics has been used when plasticity spreads over the ligament or the whole specimen. Then, the theoretic basis of the J-Integral breaks down; the value obtained with the J-Integral's definitions is a still usable parameter. The Crack - Opening - Displacement, COD, also is still a measure of the singularity's severity in the crack-tip surrounding (whom description is not necessary). These observations stem from many experiments conducted on traction specimens, with central or lateral cracks, and shape factor ranging from 0.2 to 0.8, width 40 or 80mm, thickness 10mm; extracted from the transverse direction of Z1 NCDU 25 20 and Z2 CND 17 13 (AISI 316 L) steel plates. The experiment did not fulfil ASTM's size requirement. Critical values of J and COD obtained here (in plane stress), from interrumpted tests or not, are practically independent of shape factor and geometry. They are very similar to the published values (AISI 316 L, 304). The net section stress in the ligament, in tension, is not a fracture parameter because it depends on width. The integral definition of J has been computed by a finite difference program analysing deformed grids in surface. These values are practically path independent here, they are in good agreement with those obtained by the compliance method [fr

  2. Ductility of Nanostructured Bainite

    Directory of Open Access Journals (Sweden)

    Lucia Morales-Rivas

    2016-12-01

    Full Text Available Nanostructured bainite is a novel ultra-high-strength steel-concept under intensive current research, in which the optimization of its mechanical properties can only come from a clear understanding of the parameters that control its ductility. This work reviews first the nature of this composite-like material as a product of heat treatment conditions. Subsequently, the premises of ductility behavior are presented, taking as a reference related microstructures: conventional bainitic steels, and TRIP-aided steels. The ductility of nanostructured bainite is then discussed in terms of work-hardening and fracture mechanisms, leading to an analysis of the three-fold correlation between ductility, mechanically-induced martensitic transformation, and mechanical partitioning between the phases. Results suggest that a highly stable/hard retained austenite, with mechanical properties close to the matrix of bainitic ferrite, is advantageous in order to enhance ductility.

  3. Nonlinear fracture mechanics investigation on the ductility of reinforced concrete beams

    Directory of Open Access Journals (Sweden)

    A. Carpinteri

    Full Text Available In the present paper, a numerical algorithm based on the finite element method is proposed for the prediction of the mechanical response of reinforced concrete (RC beams under bending loading. The main novelty of such an approach is the introduction of the Overlapping Crack Model, based on nonlinear fracture mechanics concepts, to describe concrete crushing. According to this model, the concrete dam- age in compression is represented by means of a fictitious interpenetration. The larger is the interpenetration, the lower are the transferred forces across the damaged zone. The well-known Cohesive Crack Model in tension and an elastic-perfectly plastic stress versus crack opening displacement relationship describing the steel reinforcement behavior are also integrated into the numerical algorithm. The application of the proposed Cohesive-Overlapping Crack Model to the assessment of the minimum reinforcement amount neces- sary to prevent unstable tensile crack propagation and to the evaluation of the rotational capacity of plastic hinges, permits to predict the size-scale effects evidenced by several experimental programs available in the literature. According to the obtained numerical results, new practical design formulae and diagrams are proposed for the improvement of the current code provisions which usually disregard the size effects.

  4. Ductile shear zones can induce hydraulically over-pressured fractures in deep hot-dry rock reservoirs: a new target for geothermal exploration?

    Science.gov (United States)

    Schrank, C. E.; Karrech, A.; Regenauer-Lieb, K.

    2014-12-01

    It is notoriously difficult to create and maintain permeability in deep hot-dry rock (HDR) geothermal reservoirs with engineering strategies. However, we predict that long-lived, slowly deforming HDR reservoirs likely contain hydraulically conductive, over-pressured fracture systems, provided that (a) the underlying lower crust and/or mantle are not entirely depleted of fluids and (b) the fracture system has not been drained into highly permeable overlying rocks. Such fracture systems could be targeted for the extraction of geothermal energy. Our prediction hinges on the notion that polycrystalline creep through matter transfer by a liquid phase (dissolution-precipitation creep) is a widespread mechanism for extracting fluids from the lower crust and mantle. Such processes - where creep cavities form during the slow, high-temperature deformation of crystalline solids, e.g., ceramics, metals, and rocks - entail the formation of (intergranular) fluid-assisted creep fractures. They constitute micron-scale voids formed along grain boundaries due to incompatibilities arising from diffusion or dislocation creep. Field and laboratory evidence suggest that the process leading to creep fractures may generate a dynamic permeability in the ductile crust, thus extracting fluids from this domain. We employed an elasto-visco-plastic material model that simulates creep fractures with continuum damage mechanics to model the slow contraction of high-heat-producing granites overlain by sedimentary rocks in 2D. The models suggest that deformation always leads to the initiation of a horizontal creep-damage front in the lower crust. This front propagates upwards towards the brittle-ductile transition (BDT) during protracted deformation where it collapses into highly damaged brittle-ductile shear zones. If the BDT is sufficiently shallow or finite strain sufficiently large, these shear zones trigger brittle faults emerging from their tips, which connect to the sub-horizontal damage

  5. Determination of slip systems and their relation to the high ductility and fracture toughness of the B2 DyCu intermetallic compound

    International Nuclear Information System (INIS)

    Cao, G.H.; Shechtman, D.; Wu, D.M.; Becker, A.T.; Chumbley, L.S.; Lograsso, T.A.; Russell, A.M.; Gschneidner, K.A.

    2007-01-01

    DyCu single crystals with CsCl-type B2 structure were tensile tested at room temperature. Slip trace analysis shows that the primary slip system in DyCu with a tensile axis orientation of is {1 1 0} and the critical resolved shear stress for {1 1 0} slip is 18 MPa. Slip traces were also observed from a secondary slip system, {1 1 0} , and this slip system appears to be a key contributor to the previously reported high ductility and high fracture toughness of polycrystalline DyCu. Transmission electron microscopy determinations of the Burgers vectors of dislocations in tensile tested specimens revealed and dislocations, with -type dislocations being more abundant. The implications of these findings for the understanding of the mechanical properties of DyCu and the large family of ductile rare earth B2 intermetallics are discussed

  6. A fracture mechanics safety concept to assess the impact behavior of ductile cast iron containers for shipping and storage of radioactive materials

    International Nuclear Information System (INIS)

    Voelzke, H.; Roedel, R.; Droste, B.

    1994-01-01

    Within the scope of the German licensing procedures for shipping and storage containers for radioactive materials made of ductile cast iron, BAM performs approval design tests including material tests to ensure the main safety goals of shielding, leaktightness and subcriticality under ''Type B accident conditions''. So far the safety assessment concept of BAM is based essentially on the experimental proof of container strength by prototype testing under most damaging test conditions in connection with complete approval design tests, and has been developed especially for cylindrical casks like CASTOR- and TN-design. In connection with the development of new container constructions such as ''cubic cast containers'', and the fast developments in the area of numerical calculation methods, there is a need for a more flexible safety concept especially considering fracture mechanics aspects.This paper presents the state of work at BAM for such an extended safety concept for ductile cast iron containers, based on a detailed brittle fracture safe design proof. The requirements on stress analysis (experimental or numerical), material properties, material qualification, quality assurance provisions and fracture mechanics safety assessment, including well defined and justified factors of safety, are described. ((orig.))

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-03-25

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

  8. Effects of boron on the fracture behavior and ductility of cast Ti–6Al–4V alloys

    International Nuclear Information System (INIS)

    Luan, J.H.; Jiao, Z.B.; Heatherly, L.; George, E.P.; Chen, G.; Liu, C.T.

    2015-01-01

    Minor amounts of boron additions have been found to greatly enhance the ductility of cast Ti–6Al–4V alloys, which was considered to be due to the grain-size refinement. In this paper, we report our interesting finding that the beneficial effect of boron on the ductility of the cast titanium alloys is due not only to the grain-size refinement but the enhancement of the prior-β grain-boundary cohesion by boron segregation at the grain boundaries, as evidenced by Auger electron microscopy

  9. Numerical Simulation of a Single-Phase Flow Through Fractures with Permeable, Porous and Non-Ductile Walls

    Directory of Open Access Journals (Sweden)

    N. Pour Mahmoud

    2017-10-01

    Full Text Available This paper attempts to study flows within fractures through a set of numerical simulations. In addition, a special care is given to hydraulic features and characteristics of fractures. The research is performed through the application of calculative fluid dynamics and a finite volume discrete schema. The investigated flows are laminar, single-phase and stable flows of water and air through fractures with penetrable walls. The selected fracture geometry is inspired from the tomographic scan of a stone fracture. Water and air are modeled in fractures with permeable walls and different permeability levels. It has been observed that in case of permeable matrixes, the friction coefficient is lower compared to impermeable matrixes. In fact permeability reduced friction. In addition, highest pressure drops were observed in areas with smaller fracture diaphragms. Nonetheless, the surrounding area of the fracture is analyzed with the consideration of Darcy's rule.

  10. Analysis of the competition between brittle and ductile fracture: application for the mechanical behaviour of C-Mn and theirs welds; Etude de la competition dechirure ductile/rupture fragile: application de la tenue mecanique des tubes en acier C-Mn et de leurs joints soudes

    Energy Technology Data Exchange (ETDEWEB)

    Le Corre, V

    2006-09-15

    This study deals with the fracture behaviour of welded thin structures in the ductile to brittle transition range. It aims to propose a criterion to define the conditions for which the risk of fracture by cleavage does not exist on a cracked structure. The literature review shows that the difficulties of prediction of the fracture behaviour of a structure are related to the dependence of the fracture probability to the mechanical fields at the crack tip. The ductile to brittle transition range thus depends on the studied geometry of the structure. A threshold stress, below which cleavage cannot take place, is defined using fracture tests on notched specimens broken at very low temperature. The finite element numerical simulation of fracture tests onspecimens in the transition range shows a linear relationship between the fracture probability and the volume exceeding the threshold stress, thus showing the relevance of the proposed criterion. Moreover, several relations are established allowing to simplify the identification of the criterion parameters. The criterion is applied to a nuclear structural C-Mn steel, by focusing more particularly on the higher boundary of the transition range. A fracture test on a full-scale pipe is designed, developed, carried out and analysed using its numerical simulation. The results show firstly that, on the structure, the transition range is shifted in temperature, compared to laboratory specimens, due to the low plasticity constraint achieved in thin structures, and secondly that the threshold stress criterion allows to estimate simply this shift. (author)

  11. An Assessment of the Ductile Fracture Behavior of Hot Isostatically Pressed and Forged 304L Stainless Steel

    Science.gov (United States)

    Cooper, A. J.; Smith, R. J.; Sherry, A. H.

    2017-05-01

    Type 300 austenitic stainless steel manufactured by hot isostatic pressing (HIP) has recently been shown to exhibit subtly different fracture behavior from that of equivalent graded forged steel, whereby the oxygen remaining in the component after HIP manifests itself in the austenite matrix as nonmetallic oxide inclusions. These inclusions facilitate fracture by acting as nucleation sites for the initiation, growth, and coalescence of microvoids in the plastically deforming austenite matrix. Here, we perform analyses based on the Rice-Tracey (RT) void growth model, supported by instrumented Charpy and J-integral fracture toughness testing at ambient temperature, to characterize the degree of void growth ahead of both a V-notch and crack in 304L stainless steel. We show that the hot isostatically pressed (HIP'd) 304L steel exhibits a lower critical void growth at the onset of fracture than that observed in forged 304L steel, which ultimately results in HIP'd steel exhibiting lower fracture toughness at initiation and impact toughness. Although the reduction in toughness of HIP'd steel is not detrimental to its use, due to the steel's sufficiently high toughness, the study does indicate that HIP'd and forged 304L steel behave as subtly different materials at a microstructural level with respect to their fracture behavior.

  12. Prediction of non-brittle fracture in the welded joint of C-Mn steel in the brittle-ductile transition domain; Prediction de la non-rupture fragile dans un joint soude en acier C-Mn dans le domaine de la transition fragile/ductile

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Thai Ha

    2009-11-15

    This work concerns the nuclear safety, specifically the secondary circuit integrity of pressurized water reactors (PWR). The problem is that of the fracture of a thin tubular structure in ferritic steel with many welded joints. The ferritic steel and weld present a brittle/ductile tenacity transition. Moreover, the welds present geometry propitious to the appearance of fatigue cracks, due to vibrations and expansions. These cracks may cause the complete fracture of the structure. The objectives of this work are to establish a criterion of non-fracture by cleavage of thin welded structures in ferritic steel, applicable to actual structures. Therefore, the present study focuses on the fracture behaviour of welded thin structures in brittle/ductile transition. It aims at developing the threshold stress model initially proposed by Chapuliot, to predict the non-brittle-fracture of this welded structure. The model is identified for the welded joint in C-Mn steel for nuclear construction, specifically in the upper part of the transition. A threshold stress, below which the cleavage cannot take place, is identified using tensile tests at low temperature on axis-symmetrical notched specimens taken in welded joint. This threshold stress is used to define the threshold volume where the maximum principal stress exceeds the threshold stress during the test. The analysis by SEM of specimen fracture surfaces shows that the gross solidification molten zone in the weld is the most likely to cleave. The relation between the brittle fracture probability and the threshold volume in the gross solidification molten zone is established via a sensitivity function, using multi-materials simulations. The model thus identified is tested for the prediction of non-brittle-fracture of SENT specimens taken in the welded joint and tested in tension. The results obtained are encouraging with regards to the transferability of the model to the actual structure. (author)

  13. Acoustic emission measurements during impacts tests for determining ductile fracture data; Ermittlung zaehbruchmechanischer Kennwerte unter schlagartiger Belastung mittels Schallemission

    Energy Technology Data Exchange (ETDEWEB)

    Richter, H.

    2000-09-01

    The document reports work for further development of methods and tests to obtain better information on the crack initiation toughness (J{sub id}) under impact loading conditions, by acoustic emission measurements. The applicability of the acoustic emission tests for the given purpose was proven by instrumented Charpy tests using modified ISO-V specimens. The physical crack initiation toughness served as the reference value for reliable evaluation of the characteristic data obtained. This reference value is derived from the crack resistance curve determined by the multi-specimen cleavage fracture method combined with data from measurements of the stretching zone width. Verification of the acoustic emission-defined initiation value included a variety of tests, as e.g. additional dynamic single-specimen methods (L-COD, magnetic emission), and supplementary tests (D3PB, pendulum impact testing machine). The test materials are various steels with different strength/toughness properties. (orig./CB) [German] Gegenstand der vorliegenden Arbeit ist die Weiterentwicklung von Verfahren zur Ermittlung der Risseinleitungszaehigkeit (J{sub id}) unter schlagartigen Belastungsbedingungen. Als Indikationsmethode fuer die duktile Rissinitiierung wurde die Messung der unter Beanspruchung im Werkstoff freigesetzten elastischen Energie - der Schallemission (SE) - genutzt. Die Eignung dieser Methode wurde im instrumentierten Kerbschlagbiegeversuch an modifizierten ISO-V-Proben geprueft. Als zuverlaessige Basis fuer eine Beurteilung der damit bestimmten Kennwerte wird die physikalische Rissinitiierungszaehigkeit angesehen. Dieser Referenzwert wird in Verbindung mit der Messung der Stretchzonenbreite aus der nach der Mehrproben-Spaltbruchmethode ermittelten Risswiderstandskurve gewonnen. Die Bestimmung des SE-definierten Initiierungswertes wurde mit zusaetzlichen dynamischen Einprobenverfahren (Laser-COD, magnetische Emission) und ergaenzenden Versuchsanordnungen (invertiertes

  14. Ductile failure modeling

    DEFF Research Database (Denmark)

    Benzerga, Ahmed Amine; Leblond, Jean Baptiste; Needleman, Alan

    2016-01-01

    Ductile fracture of structural metals occurs mainly by the nucleation, growth and coalescence of voids. Here an overview of continuum models for this type of failure is given. The most widely used current framework is described and its limitations discussed. Much work has focused on extending void...... growth models to account for non-spherical initial void shapes and for shape changes during growth. This includes cases of very low stress triaxiality, where the voids can close up to micro-cracks during the failure process. The void growth models have also been extended to consider the effect of plastic...... anisotropy, or the influence of nonlocal effects that bring a material size scale into the models. Often the voids are not present in the material from the beginning, and realistic nucleation models are important. The final failure process by coalescence of neighboring voids is an issue that has been given...

  15. Hot ductility behavior of boron microalloyed steels

    International Nuclear Information System (INIS)

    Lopez-Chipres, E.; Mejia, I.; Maldonado, C.; Bedolla-Jacuinde, A.; Cabrera, J.M.

    2007-01-01

    The current study analyses the influence of boron contents (between 29 and 105 ppm) on the hot ductility of boron microalloyed steels. For this purpose, hot tensile tests were carried out at different temperatures (700, 800, 900 and 1000 deg. C) at a constant true strain rate of 0.001 s -1 . In general, results revealed an improvement of the hot ductility of steels at increasing boron content. At 700, 900 and 1000 deg. C the ductility is higher than at 800 deg. C, where boron microalloyed steels exhibit a region of ductility loss (trough region). Likewise, dynamic recrystallization only occurred at 900 and 1000 deg. C. The fracture surfaces of the tested steels at temperatures giving the high temperature ductility regime show that the fracture mode is a result of ductile failure, whereas it is ductile-brittle failure in the trough region. Results are discussed in terms of dynamic recrystallization and boron segregation towards austenite grain boundaries, which may retard the formation of pro-eutectoid ferrite and increase grain boundary cohesion

  16. Rock types and ductile structures on a rock domain basis, and fracture orientation and mineralogy on a deformation zone basis. Preliminary site description. Forsmark area - version 1.2

    Energy Technology Data Exchange (ETDEWEB)

    Stephens, Michael [Geological Survey of Sweden, Uppsala (Sweden); Forssberg, Ola [Golder Associates AB, Uppsala (Sweden)

    2006-09-15

    This report presents the results of the analysis of base geological data in order to establish the dominant rock type, the subordinate rock types and the orientation of ductile mineral fabrics within each rock domain included in the regional geological model, version 1.2. An assessment of the degree of homogeneity of each domain is also provided. The analytical work has utilised the presentation of data in the form of histograms and stereographic projections. Fisher means and K values or best-fit great circles and corresponding pole values have been calculated for the ductile structural data. These values have been used in the geometric modelling of rock domains in the regional model, version 1.2. Furthermore, all analytical results have been used in the assignment of properties to rock domains in this model. A second analytical component reported here addresses the orientation and mineralogy of fractures in the deterministic deformation zones that are included in the regional geological model, version 1.2. The analytical work has once again utilised the presentation of data in the form of histograms and stereographic projections. Fisher means and K values are presented for the orientation of fracture sets in the deterministic deformation zones that have been identified with the help of new borehole data. The frequencies of occurrence of different minerals along the fractures in these deformation zones as well as the orientation of fractures in the zones, along which different minerals occur, are also presented. The results of the analyses have been used in the establishment of a conceptual structural model for the Forsmark site and in the assignment of properties to deterministic deformation zones in model version 1.2.

  17. A Study on Ductility of Prestressed Concrete Pier Based on Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    H. Wang

    2016-12-01

    Full Text Available The ductility of prestressed concrete pier is studied based on response surface methodology. Referring to the pervious prestressed concrete pier, based on Box-Behnken design, the ductility of 25 prestressed concrete piers is calculated by numerical method. The relationship between longitudinal reinforcement ratio, shear reinforcement ratio, prestressed tendon quantity, concrete compressive strength and ductility factor is gotten. The influence of the longitudinal reinforcement ratio, the shear reinforcement ratio, the prestressed tendon quantity and concrete compressive strength to curvature ductility is discussed. Then the ductility regression equation is deduced. The result showed that the influence of the prestressed tendon quantity to the ductility of prestressed concrete pier is significant. With the increasing of the prestressed tendon quantity, the curvature ductility curved reduces. With the increasing of shear reinforcement ratio and compressive strength of concrete, the curvature ductility increases linearly. And the influence of the longitudinal reinforcement ratio to ductility of the prestressed concrete pier is insignificant.

  18. Hydrogen induced ductility losses in austenitic stainless steel welds

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, J.A.; West, A.J.

    1978-06-01

    The effect of hydrogen on the tensile behavior of austenitic stainless steel welds was studied in two AISI 300 series alloys and two nitrogen strengthened alloys. The microstructure of these welds typically contained several percent ferrite in an austenite matrix. Hydrogen was found to reduce the ductility of all welds; however, the severity of ductility loss decreased with increasing stacking fault energy, as observed in previous studies on wrought material. In the lowest stacking fault energy welds, 304L and 308L, hydrogen changed the fracture mode from simple rupture to a mixed mode of ductile and brittle fracture associated with the austenite ferrite interface. Higher stacking fault energy welds, 309S and 22-13-5, showed smaller losses in ductility. In these materials hydrogen assisted the ductile rupture process by aiding void growth and coalescence, without changing the fracture mode. Varying the amount of ferrite from approximately one to 10 percent had no significant effect on performance in hydrogen.

  19. Ductile failure X-prize.

    Energy Technology Data Exchange (ETDEWEB)

    Cox, James V.; Wellman, Gerald William; Emery, John M.; Ostien, Jakob T.; Foster, John T.; Cordova, Theresa Elena; Crenshaw, Thomas B.; Mota, Alejandro; Bishop, Joseph E.; Silling, Stewart Andrew; Littlewood, David John; Foulk, James W., III; Dowding, Kevin J.; Dion, Kristin; Boyce, Brad Lee; Robbins, Joshua H.; Spencer, Benjamin Whiting

    2011-09-01

    Fracture or tearing of ductile metals is a pervasive engineering concern, yet accurate prediction of the critical conditions of fracture remains elusive. Sandia National Laboratories has been developing and implementing several new modeling methodologies to address problems in fracture, including both new physical models and new numerical schemes. The present study provides a double-blind quantitative assessment of several computational capabilities including tearing parameters embedded in a conventional finite element code, localization elements, extended finite elements (XFEM), and peridynamics. For this assessment, each of four teams reported blind predictions for three challenge problems spanning crack initiation and crack propagation. After predictions had been reported, the predictions were compared to experimentally observed behavior. The metal alloys for these three problems were aluminum alloy 2024-T3 and precipitation hardened stainless steel PH13-8Mo H950. The predictive accuracies of the various methods are demonstrated, and the potential sources of error are discussed.

  20. Transformation plasticity in ductile solids

    Energy Technology Data Exchange (ETDEWEB)

    Olson, G.B.

    1993-02-01

    Research has addressed the role of martensitic transformation plasticity in the enhancement of toughness in high-strength austenitic steels, and the enhancement of formability in multiphase low-alloy sheet steels. In the austenitic steels, optimal processing conditions have been established to achieve a significant increase in strength level, in order to investigate the interaction of strain-induced transformation with the microvoid nucleation and shear localization mechanisms operating at ultrahigh strength levels. The stress-state dependence of transformation and fracture mechanisms has been investigated in model alloys, comparing behavior in uniaxial tension and blunt-notch tension specimens. A numerical constitutive model for transformation plasticity has been reformulated to allow a more thorough analysis of transformation/fracture interactions. Processing of a new low alloy steel composition has been optimized to stabilize retained austenite by isothermal bainitic transformation after intercritical annealing. Preliminary results show a good correlation of uniform ductility with the austenite amount and stability.

  1. Particle size evolution in non-adhered ductile powders during mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero-Paz, J. [Centro de Investigaciones en Materiales y Metalurgica, UAEH (Mexico); Robles-Hernandez, F.C.; Hernandez-Silva, D.; Jaramillo-Vigueras, D. [Dept. de Ingenieria Metalurgica, ESIQIE - Inst. Politecnico Nacional, Mexico D.F. (Mexico); Martinez-Sanchez, R. [Centro de Investigacion en Materiales Avanzados, Chihuahua (Mexico)

    2001-07-01

    The interaction among events as deformation, cold-welding and fracture, occurring during the mechanical milling of powders is unclear and controversial. We believe that the understanding of such interaction can be deduced from particle size evolution studies. It is well known that the elemental ductile powders adhere to the milling media. However when some of these powders are combined to form an alloy by milling, the adherence phenomenon is not observed. Systems which include ductile powders, such as, Cu-15at.%Al, Co-68at.%Al and Ni-25at.%Al were processed with not adherence to the milling media, thus allowing to follow up the particle size evolution during the complete milling process. The particle size was measured by the sedimentation-photometry technique. Those results were supported by scanning and transmission electron microscopy. The results showed a high proportion near 95% in number of particles of submicrometric size at early milling times for the three systems. However its particle size evolution for each system was different. Such findings can be important to understand some mechanisms as the grain size refinement, the alloy formation and the microstructural evolution. In the studied systems, the particle size measurements are presented based on volume or mass, area, line and number of the particles. The particle size results based on volume and line or number of the particles can give an idea of the evolution of the biggest particles and the finest ones respectively during the milling. Also the behavior of the complete particle system can be deduced from the results based in the area of the particles. Results of particle size as well as observations by microscopy helped to suggest the particle size and shape evolution of the studied systems. Such findings were employed to previously propose a grain size refinement mechanism for ductile powder systems non-adherent to the milling media during the mechanical alloying. (orig.)

  2. Highsilicone Austempered Ductile Iron

    Directory of Open Access Journals (Sweden)

    Kochański A.

    2014-03-01

    Full Text Available Ductile iron casts with a higher silicone content were produced. The austempering process of high silicone ductile iron involving different austempering times was studied and the results presented. The results of metallographical observations and tensile strength tests were offered. The obtained results point to the fact that the silicone content which is considered as acceptable in the literature may in fact be exceeded. The issue is viewed as requiring further research

  3. Numerical modelling of Charpy-V notch test by local approach to fracture. Application to an A508 steel in the ductile-brittle transition range

    International Nuclear Information System (INIS)

    Tanguy, B.

    2001-07-01

    Ferritic steels present a transition of the rupture mode which goes progressively of a brittle rupture (cleavage) to a ductile rupture when the temperature increases. The following of the difference of the transition temperature of the PWR vessel steel by the establishment of toughness curves makes of the Charpy test an integrating part of the monitoring of the French PWR reactors. In spite of the advantages which are adapted to it in particular its cost, the Charpy test does not allow to obtain directly a variable which characterizes a crack propagation resistance as for instance the toughness used for qualifying the mechanical integrity of a structure. This work deals with the establishment of the through impact strength-toughness in the transition range of the vessel steel: 16MND5 from a non-empirical approach based on the local approach of the rupture. The brittle rupture is described by the Beremin model (1983), which allows to describe the dispersion inherent in this rupture mode. The description of the brittle fissure is carried out by the GTN model (1984) and by the Rousselier model (1986). This last model has been modified in order to obtain a realistic description of the brittle damage in the case of fast solicitations and of local heating. The method proposed to determine the parameters of the damage models depends only of tests on notched specimens and of the inclusion data of the material. The behaviour is described by an original formulation parametrized in temperature which allows to describe all the tests carried out in this study. Before using this methodology, an experimental study of the behaviour and of the rupture modes of the steel 16MND5 has been carried out. From the toughness tests carried out in quasi-static and dynamical conditions, it has been revealed that this steel does not present important unwedging of its toughness curve due to the velocity effect. In the transition range, local heating of about 150 C have been measured in the root

  4. Application of stable crack growth in fracture assessment of defects in ductile materials; Tillaempning av stabil spricktillvaext vid brottmekanisk bedoemning av defekter i sega material

    Energy Technology Data Exchange (ETDEWEB)

    Dillstroem, Peter (Inspecta Technology AB, Stockholm (Sweden))

    2009-06-15

    This report goes through the use of methods/standards, which consider stable (J-controlled) crack growth. We have demonstrated the following: - ASME XI, App. C, App. H, which deals with analysis of stainless steel and ferritic piping, take account of stable growth. In App. C, this corresponds to the inclusion of stable growth up to DELTAa approx 10 mm. - R6-method, BS 7910:1999 and ASME XI, Code Case N-494, contains an established formalism to take account of stable growth. A prerequisite is that you have access to relevant and authentic material data in the form of fracture resistance K{sub k}/J{sub k} and J{sub r} curves. - All of the above methods/standards are applicable in the nuclear context. We reported also that required to produce relevant and valid data (fracture resistance K{sub k}/J{sub k} and J{sub r} curves) to be used for the analysis of stable growth. This report does not specify how much stable crack that can be counted at a Safety Assessment

  5. Hot Ductility Behavior of a Peritectic Steel during Continuous Casting

    Directory of Open Access Journals (Sweden)

    Mustafa Merih Arıkan

    2015-06-01

    Full Text Available Hot ductility properties of a peritectic steel for welded gas cylinders during continuous casting were studied by performing hot tensile tests at certain temperatures ranging from 1200 to 700 °C for some cooling rates by using Gleeble-3500 thermo-mechanical test and simulation machine in this study. The effects of cooling rate and strain rate on hot ductility were investigated and continuous casting process map (time-temperature-ductility were plotted for this material. Reduction of area (RA decreases and cracking susceptibility increases during cooling from solidification between certain temperatures depending on the cooling rate. Although the temperatures which fracture behavior change upon cooling during continuous casting may vary for different materials, it was found that the type of fracture was ductile at 1100 and 1050 °C; semi-ductile at 1000 °C, and brittle at 800 °C for the steel P245NB. There is a ductility trough between 1000 and 725 °C. The ductility trough gets slightly narrower as the cooling rate decreases.

  6. Identification Damage Model for Thermomechanical Degradation of Ductile Heterogeneous Materials

    Science.gov (United States)

    Amri, A. El; Yakhloufi, M. H. El; Khamlichi, A.

    2017-05-01

    The failure of ductile materials subject to high thermal and mechanical loading rates is notably affected by material inertia. The mechanisms of fatigue-crack propagation are examined with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials, such as metals, and corresponding behavior in brittle materials, such as intermetallic and ceramics. Numerical simulations of crack propagation in a cylindrical specimen demonstrate that the proposed method provides an effective means to simulate ductile fracture in large scale cylindrical structures with engineering accuracy. The influence of damage on the intensity of the destruction of materials is studied as well.

  7. Ductile transplutonium metal alloys

    Science.gov (United States)

    Conner, William V.

    1983-01-01

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  8. Intrinsic ductility and environmental embrittlement of binary Ni3Al

    International Nuclear Information System (INIS)

    George, E.P.; Liu, C.T.; Pope, D.P.

    1993-01-01

    Polycrystalline, B-free Ni 3 Al (23.4 at.% Al), produced by cold working and recrystallizing a single crystal, exhibits room temperature tensile ductilities of 3-5% in air and 13-16% in oxygen. These ductilities are considerably higher than anything previously reported, and demonstrate that the 'intrinsic' ductility of Ni 3 Al is much higher than previously thought. They also show that the moisture present in ordinary ambient air can severely embrittle Ni 3 Al (ductility decreasing from a high of 16% in oxygen to a low of 3% in air). Fracture is predominantly intergranular in both air and oxygen. This indicates that, while moisture can further embrittle the GBs in Ni 3 Al, they persist as weak links even in the absence of environmental embrittlement. However, they are not 'intrinsically brittle' as once thought, since they can withstand relatively large plastic deformations prior to fracture. Because B essentially eliminates environmental embrittlement in Ni 3 Al - and environmental embrittlement is a major cause of poor ductility in B-free Ni 3 Al - it is concluded that a significant portion of the so-called B effect must be related to suppression of moisture-induced environmental embrittlement. However, since B-doped Ni 3 Al fractures transgranularly, whereas B-free Ni 3 Al fractures predominantly intergranularly, B must have the added effect that it strengthens the GBs. A comparison with the earlier work on Zr-doped Ni 3 Al shows that Zr improves the ductility of Ni 3 Al, both in air and (and even more dramatically) in oxygen. While the exact mechanism of this ductility improvement is not clear at present, Zr appears to have more of an effect on (enhancing) GB strength than on (suppressing) environmental embrittlement

  9. The austempering study of alloyed ductile iron

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-07-01

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

  10. Analyses of cavitation instabilities in ductile metals

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2007-01-01

    , and also tests for a thin ductile metal layer bonding two ceramic blocks have indicated rapid void growth. Analyses for these material configurations are discussed here. When the void radius is very small, a nonlocal plasticity model is needed to account for observed size-effects, and recent analyses......Cavitation instabilities have been predicted for a single void in a ductile metal stressed under high triaxiality conditions. In experiments for a ceramic reinforced by metal particles a single dominant void has been observed on the fracture surface of some of the metal particles bridging a crack...... for the influence of such size-effects on cavitation instabilities are presented. When a metal contains a distribution of micro voids, and the void spacing compared to void size is not extremely large, the surrounding voids may affect the occurrence of a cavitation instability at one of the voids. This has been...

  11. A review of macroscopic ductile failure criteria.

    Energy Technology Data Exchange (ETDEWEB)

    Corona, Edmundo; Reedlunn, Benjamin

    2013-09-01

    The objective of this work was to describe several of the ductile failure criteria com- monly used to solve practical problems. The following failure models were considered: equivalent plastic strain, equivalent plastic strain in tension, maximum shear, Mohr- Coulomb, Wellman's tearing parameter, Johnson-Cook and BCJ MEM. The document presents the main characteristics of each failure model as well as sample failure predic- tions for simple proportional loading stress histories in three dimensions and in plane stress. Plasticity calculations prior to failure were conducted with a simple, linear hardening, J2 plasticity model. The resulting failure envelopes were plotted in prin- cipal stress space and plastic strain space, where the dependence on stress triaxiality and Lode angle are clearly visible. This information may help analysts select a ductile fracture model for a practical problem and help interpret analysis results.

  12. Ductile Binder Phase For Use With Almgb14 And Other Hard Ceramic Materials

    Science.gov (United States)

    Cook, Bruce A.; Russell, Alan; Harringa, Joel

    2005-07-26

    This invention relates to a ductile binder phase for use with AlMgB14 and other hard materials. The ductile binder phase, a cobalt-manganese alloy, is used in appropriate quantities to tailor good hardness and reasonable fracture toughness for hard materials so they can be used suitably in industrial machining and grinding applications.

  13. Improving the low temperature ductility of NiAl

    Science.gov (United States)

    Guha, Sumit; Munroe, Paul R.; Baker, Ian

    1989-01-01

    As part of a study aimed at developing a ductile NiAl-based alloy, ingots of Ni-Fe-Al alloys were cast and hot extruded to rods. The purpose of the iron additions was two-fold viz; to produce a change in the slip vector from 001 to 111 line and, in one alloy, to add a L1(2)-structured ductile second phase. Extruded Ni-20Al-30Fe was two-phase, containing a pro-eutectic B2 phase in a fine lamellar structure of B2+L1(2) phases. Room temperature tensile testing of both single extruded and double extruded alloys resulted in 8-percent and 22-percent plastic elongation and yield stresses of 850 and 760 MPa, respectively. Fracture in both cases occurred by ductile tearing of the eutectic and transgranular cleavage of the proeutectic phase at 1350 MPa. The ductility in double extruded condition is higher than that reported earlier in rapidly solidified wires by Inoue et al. (1984). By comparison, extruded single-phase B2-structured Ni-30Al-20Fe exhibited a fracture strength of 780 MPa, no plasticity, and a mixture of intergranular fracture and transgranular cleavage. This is contrast to earlier work by Inoue et al. where a yield stress of 400 MPa, 5 percent plastic strain, and a mixture of dimple and intergranular fracture was reported.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-05-01

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

  15. Physical factors controlling the ductility of bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y. [Central South University, China; Liu, Chain T [ORNL; Zhang, Z. [University of Tennessee, Knoxville (UTK); Keppens, V. [University of Tennessee, Knoxville (UTK)

    2008-01-01

    In order to identify key physical factor controlling the deformation and fracture behavior of bulk metallic glasses (BMGs), we compiled and analyzed the elastic moduli and compressive ductility for BMGs. In addition, new modulus data were generated in the critical ranges in order to facilitate the analysis. We have found that the intrinsic ductility of BMGs can be correlated with the bulk-to-shear modulus ratio B/G according to Pugh's [Philos. Mag. 45, 823 (1954) ] rule. In some individual BMG systems, for example, Fe based, the relationship seems to be very clear. The physical meaning of this correlation is discussed in terms of atomic bonding and connectivity.

  16. Dislocation model of fracture

    International Nuclear Information System (INIS)

    Kull', L.M.

    1987-01-01

    Papers dealing with study on mechanisms of submicricrack formation and propagation using dislocation representations are analyzed. Cases of brittle and ductile fracture of materials as well as models of dislocationless (amorphous) zone at the growing crack tip are considered. Dislocation models of fracture may be used when studying the processes of deformation and accumulation of damages in elements of nuclear facilities

  17. Friction welding of ductile cast iron using interlayers

    International Nuclear Information System (INIS)

    Winiczenko, Radoslaw; Kaczorowski, Mieczyslaw

    2012-01-01

    Highlights: → The results of the study of the friction welding of ductile cast iron using interlayers are presented. → The results of the analysis shows that the joint has the tensile strength compared to that of basic material. → In case of ductile cast iron, it is possible to reach the tensile strength equals even 700 MPa. → The process of friction welding was accompanied with diffusion of Cr, Ni and C atoms across the interface. -- Abstract: In this paper, ductile cast iron-austenitic stainless steel, ductile cast iron-pure Armco iron and ductile cast iron-low carbon steel interlayers were welded, using the friction welding method. The tensile strength of the joints was determined, using a conventional tensile test machine. Moreover, the hardness across the interface of materials was measured on metallographic specimens. The fracture surface and microstructure of the joints was examined using either light stereoscope microscopy as well as electron microscopy. In this case, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied. The results of the analysis shows that the joint has the tensile strength compared to that of basic material. In case of ductile cast iron, it is possible to reach the tensile strength equals even 700 MPa. It was concluded that the process of friction welding was accompanied with diffusion of Cr, Ni and C atoms across the ductile cast iron-stainless steel interface. This leads to increase in carbon concentration in stainless steel where chromium carbides were formed, the size and distribution of which was dependent on the distance from the interface.

  18. Quality assurance of the reactor pressure vessel of nuclear power plants. Determination of the fracture toughness KIC above the ductile-brittle transition region on small test specimens by means of a conformal mapping

    International Nuclear Information System (INIS)

    Ullrich, G.; Krompholz, K.

    1994-01-01

    The ''surveillance-programs'' for the determination of the mechanical properties of reactor pressure vessel (RPV) materials, as a function of the neutron dose, include impact and tensile tests for the boiling water reactor; while for pressurized water reactors additional wedge opening load specimens (WOL), for the measurement of the fracture toughness K IC at low temperatures, are utilized. While the Charpy impact toughness gives the total magnitude of energy, which indicates the change of the material state, e.g. the state of embrittlement, the fracture toughness, I IC , gives a base for mechanical calculations. This is of importance for components in which cracks or flaws are assumed. The mechanical analysis, and its relevance to safety assessments, depends on the knowledge of different parameters such as geometry of the structure and flaws, and load history of the structure. Fracture mechanical methods play an important role, if the leak-before-fracture problem is considered. Within the frame work of fracture mechanical methods, only the influence of assumed macroscopic cracks on the structural behaviour can be handled. Flaw formation processes in flaw-free structures, as well as the treatment of short flaws, can not currently be included. In the regime of low and intermediate temperatures (for ferritic and austenitic materials, normally below 400 o C), the rules of linear elastic fracture mechanics (LEFM) and elasto-plastic fracture mechanics (EPFM) are applied, some of which are already part of the code cases. (author) 5 figs., 32 refs

  19. Correlation of nodular austempered ductile iron (ADI) microstructural parameters and fatigue properties using an approach based on fracture mechanics; Correlacao entre parametros microestruturais do ferro fundido nodular austemperado (ADI) com suas propriedades a fadiga utilizando uma abordagem baseada na mecanica de fratura

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Jose Felipe [Universidade de Itauna (UIT), MG (Brazil). Faculdade de Engenharia; Fonseca, Vinicius Rizzuti; Godefroid, Leonardo Barbosa [Universidade Federal de Ouro Preto (UFOP), MG (Brazil). Escola de Minas; Ribeiro, Gabriel de Oliveira [Universidade Federal de Minas Gerais (UFMG), MG (Brazil). Departamento de Engenharia de Estruturas

    2010-07-01

    An investigation has been accomplished to check the effect of temperature and austempering time on austempered ductile iron (ADI) properties by means of fracture toughness (K{sub C}) and fatigue threshold (∆K{sub th}) tests. The correlation of ADI microstructural parameters and ADI two mechanical parameters: KC and Kth, is evaluated. Three sets of samples have ben extracted from ADI casting Y blocks produced in industrial conditions.and austenitized at 900°C for 1.5 hour. The austempering process has been performed in the following ways: the first set was austenitized at 300 deg C for 4 hours, the second set at 360°C for 1.5 hour and the third at 360°C for 0.6 hour. These distinct austempering processes have been adopted in order to obtain distinct microstructures containing austenite with two different carbon rates and two ferritic cell sizes. The materials have been characterized by means of optical and electronic microscopy, X-ray diffraction and mechanical tests. All materials have presented equivalent fatigue crack propagation rates, fracture toughness in the range between 94 and 128 MPa·m{sup 1/2} and ∆K{sub th} in the range between 5,7 and 6,4 MPa·m{sup 1/2}. The experimental results have confirmed the effect of microstructural properties (austenitic volumetric rate, austenitic carbon rate, ferritic cell size, total matrix carbon content) on fracture toughness (K{sub C}) and fatigue threshold (∆K{sub th}). Further, it was found that following parameters: fracture toughness (K{sub C}), fatigue threshold ((∆K{sub th}) and impact strength are correlated with the total matrix carbon content and ferritic cell size. (author)

  20. Ductile mode grinding of reaction-bonded silicon carbide mirrors.

    Science.gov (United States)

    Dong, Zhichao; Cheng, Haobo

    2017-09-10

    The demand for reaction-bonded silicon carbide (RB-SiC) mirrors has escalated recently with the rapid development of space optical remote sensors used in astronomy or Earth observation. However, RB-SiC is difficult to machine due to its high hardness. This study intends to perform ductile mode grinding to RB-SiC, which produces superior surface integrity and fewer subsurface damages, thus minimizing the workload of subsequent lapping and polishing. For this purpose, a modified theoretical model for grain depth of cut of grinding wheels is presented, which correlates various processing parameters and the material characteristics (i.e., elastic module) of a wheel's bonding matrix and workpiece. Ductile mode grinding can be achieved as the grain depth of cut of wheels decreases to be less than the critical cut depth of workpieces. The theoretical model gives a roadmap to optimize the grinding parameters for ductile mode grinding of RB-SiC and other ultra-hard brittle materials. Its feasibility was validated by experiments. With the optimized grinding parameters for RB-SiC, the ductile mode grinding produced highly specular surfaces (with roughness of ∼2.2-2.8  nm Ra), which means the material removal mechanism of RB-SiC is dominated by plastic deformation rather than brittle fracture. Contrast experiments were also conducted on fused silica, using the same grinding parameters; this produced only very rough surfaces, which further validated the feasibility of the proposed model.

  1. Displacement-length scaling of brittle faults in ductile shear.

    Science.gov (United States)

    Grasemann, Bernhard; Exner, Ulrike; Tschegg, Cornelius

    2011-11-01

    Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement-distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow.

  2. Displacement–length scaling of brittle faults in ductile shear

    Science.gov (United States)

    Grasemann, Bernhard; Exner, Ulrike; Tschegg, Cornelius

    2011-01-01

    Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement–distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow. PMID:26806996

  3. Soldering with ductile active solders

    Czech Academy of Sciences Publication Activity Database

    Dupák, Jan; Ustohal, V.

    2001-01-01

    Roč. 16, č. 6 (2001), s. 855 - 861 ISSN 1042-6914 Institutional research plan: CEZ:AV0Z2065902 Keywords : active solders * ductile solders * cryogenics devices Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.288, year: 2001

  4. Physical fracture properties (fracture surfaces as information sources; crackgrowth and fracture mechanisms; exemples of cracks)

    International Nuclear Information System (INIS)

    Meny, Lucienne.

    1979-06-01

    Fracture surfaces are considered as a useful source of informations: an introduction to fractography is presented; the fracture surface may be observed through X ray microanalysis, and other physical methods such as Auger electron spectroscopy or secundary ion emission. The mechanisms of macroscopic and microscopic crackgrowth and fracture are described, in the case of unstable fracture (cleavage, ductile with shear, intergranular brittleness) and of progressive crack propagation (creep, fatigue). Exemples of cracks are presented in the last chapter [fr

  5. An austempering study of ductile iron alloyed with copper

    Directory of Open Access Journals (Sweden)

    OLIVERA ERIC

    2005-07-01

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

  6. A variational void coalescence model for ductile metals

    KAUST Repository

    Siddiq, Amir

    2011-08-17

    We present a variational void coalescence model that includes all the essential ingredients of failure in ductile porous metals. The model is an extension of the variational void growth model by Weinberg et al. (Comput Mech 37:142-152, 2006). The extended model contains all the deformation phases in ductile porous materials, i.e. elastic deformation, plastic deformation including deviatoric and volumetric (void growth) plasticity followed by damage initiation and evolution due to void coalescence. Parametric studies have been performed to assess the model\\'s dependence on the different input parameters. The model is then validated against uniaxial loading experiments for different materials. We finally show the model\\'s ability to predict the damage mechanisms and fracture surface profile of a notched round bar under tension as observed in experiments. © Springer-Verlag 2011.

  7. Multiphase Ausformed Austempered Ductile Iron

    Directory of Open Access Journals (Sweden)

    Soliman M.

    2017-09-01

    Full Text Available Ductile iron was subjected to a total true strain (φt of 0.3 either by applying φt in the austenite region or by apportioning it through applying a true strain of 0.2 in the austenite region before quenching to austempering temperature (TA of 375°C, where a true strain of 0.1 is applied (ausforming. Additionally, two types of matrices were produced in the ductile iron, namely ausferritic and ferritic-ausferritic matrices. The ferrite is introduced to the matrix by intercritical annealing after austenitization. Dilatometric measurements as well as microstructure examination showed a fast ausferrite transformation directly after applying φA and that the introduction of ferrite to the matrix resulted in a remarkable acceleration of the ausferrite formation. The transformation kinetics, microstructure evolution, hardness and compression properties are studied.

  8. Energetic approach for ductile tearing; Approche energetique de la dechirure ductile

    Energy Technology Data Exchange (ETDEWEB)

    Marie, St

    1999-07-01

    This study focuses on ductile crack initiation and propagation. It aims to propose an approach for the engineer allowing the prediction of the evolution of cracks in large scale components, from parameters determined on laboratory specimens. A crack initiation criterion, defining a J{sub i} tenacity related to crack tip blunting proposed in the literature is validated in the study. This criterion is shown to be transferable from laboratory specimens to structures. The literature review shows that an approach based on the dissipated energy in the fracture process during propagation offers an economical and simple solution to simulate large crack growth. A numerical method is proposed to estimate this fracture energy. The existence of an energy parameter G{sub fr} is shown, by simulating the propagation by the simultaneous release of several elements and by the use of the Rice integral with an original integration path. This parameter represents the needed energy for a unit crack extension and appears to be intrinsic to the material. A global energy statement allows to relate this parameter to a variation of the plastic part of J integral. It offers a second numerical method to simulate the propagation just from stationary numerical calculations, as well as the elaboration of a simplified method. This approach, using two parameters J{sub i} and G{sub fr}, intrinsic to the material and experimentally measurable on specimens, is validated on many tests such as crack pipes subjected to four points bending and cracked rings in compression. For example, this approach allows to model up to 90 mm ductile tearing in a pipe with a circumferential through-wall crack in ferritic steel, or to anticipate the evolution of a semi-elliptical crack in an aged austenitic ferritic steel plate subjected to bending. (author)

  9. Fracture performance of high strength steels, aluminium and magnesium alloys during plastic deformation

    Directory of Open Access Journals (Sweden)

    Yu Haiyan

    2015-01-01

    Full Text Available A series of uniaxial tension tests were performed for 5052 and 6061 aluminum alloys, AZ31B magnesium alloy, TRIP600 and DP600 steels, to obtain a better understanding of their fracture performance. Scanning electron microscope (SEM observation of the microstructure evolution was conducted. The dimple structure, orientation relationship between the fracture surface and tensile direction, necking behavior were analyzed. The fracture mechanism and fracture mode of each material was discussed in detail. The results show that TRIP600 steel is subject to a typical inter-granular ductile fracture combined by shear fracture. DP600 steel belongs to mainly ductility mixed with normal fracture. Both 5052 and 6061 aluminum alloys are subject to a mixed ductility fracture and brittle fracture. AA5052 and AA6061 belong to a typical shear fracture and a normal fracture, respectively. Magnesium AZ31B is typical of a brittle fracture combined with normal fracture.

  10. Effect of Cu on the microstructural and mechanical properties of as-cast ductile iron

    International Nuclear Information System (INIS)

    Tiwari, Siddhartha; Das, J.; Ray, K.K.; Kumar, Hemant; Bhaduri, A.

    2012-01-01

    The application of ductile cast iron in the heavy engineering components like, cask for the storage and transportation of radioactive materials, demands high strength with improved fracture toughness in as cast condition. The mechanical properties and fracture toughness of as-cast ductile iron (DI) is directly related to its structure property which can be controlled by proper inoculation, alloying elements and cooling rate during solidification. The aim of the present investigation is to study the effect of varying amount of Cu (0.07%, 0.11%, and 0.16%) with 1% Ni in the microstructural development of as-cast ductile iron with emphasis on its mechanical properties and fracture toughness. Three different ductile irons have been prepared using induction furnace in batches of 300 kg following industrial practice. Microstructural features (amount of phases, morphology, size and count of graphite nodules) and mechanical properties (tensile strength and hardness) of prepared DI were determined using standard methods. Dynamic fracture toughness was measured using instrumented Charpy impact test on pre-cracked specimens following the standard ISO-FDIS-26843. Additionally, fracture surfaces of broken tensile and pre-cracked specimens were observed by SEM to study the micro-mechanism of fracture. The pearlite fraction and the nodule count are found to increase with increasing amount of copper in ferritic-pearlitic matrix. The hardness and strength values are found to increase with increasing amount of pearlite whereas fracture toughness decreases. Fractographs of broken specimens exhibited decohesion of graphite, crack propagation from graphite interface and transgranular fracture of ferrite. (author)

  11. Ductile failure simulation of tensile plates with multiple through wall cracks based on damage mechanics

    International Nuclear Information System (INIS)

    Young, Jeon Jun; Kim, Nak Hyun; Oh, Chang Sik; Kim, Yun Jae

    2012-01-01

    This paper proposes a simple numerical method, based on the stress modified fracture strain damage model with the stress reduction technique, for predicting the failure behaviors of ductile plates with multiple through wall cracks. This technique is implemented using the user defined subroutines provided in ABAQUS. For validation, the results simulated using the proposed method are compared with published experimental data of Japanese researchers

  12. Evaluation of Ductile Iron for Offshore Application

    OpenAIRE

    Jørgensen, Mats Røed

    2017-01-01

    Master's thesis in Mechanical engineering The possibility of using ductile iron as a construction material for offshore applications have been investigated. If ductile iron is considered as being a substitute material forwelded steel, it can create a larger freedom for engineers in a design process as well as provide benefits regarding strength and cost.The issue of getting ductile iron approved as a reliable substitute material for steel is a statement made by DNV GL, being that cast iron...

  13. Rhenium Alloys as Ductile Substrates for Diamond Thin-Film Electrodes.

    Science.gov (United States)

    Halpern, Jeffrey M; Martin, Heidi B

    2014-02-01

    Molybdenum-rhenium (Mo/Re) and tungsten-rhenium (W/Re) alloys were investigated as substrates for thin-film, polycrystalline boron-doped diamond electrodes. Traditional, carbide-forming metal substrates adhere strongly to diamond but lose their ductility during exposure to the high-temperature (1000°C) diamond, chemical vapor deposition environment. Boron-doped semi-metallic diamond was selectively deposited for up to 20 hours on one end of Mo/Re (47.5/52.5 wt.%) and W/Re (75/25 wt.%) alloy wires. Conformal diamond films on the alloys displayed grain sizes and Raman signatures similar to films grown on tungsten; in all cases, the morphology and Raman spectra were consistent with well-faceted, microcrystalline diamond with minimal sp 2 carbon content. Cyclic voltammograms of dopamine in phosphate-buffered saline (PBS) showed the wide window and low baseline current of high-quality diamond electrodes. In addition, the films showed consistently well-defined, dopamine electrochemical redox activity. The Mo/Re substrate regions that were uncoated but still exposed to the diamond-growth environment remained substantially more flexible than tungsten in a bend-to-fracture rotation test, bending to the test maximum of 90° and not fracturing. The W/Re substrates fractured after a 27° bend, and the tungsten fractured after a 21° bend. Brittle, transgranular cleavage fracture surfaces were observed for tungsten and W/Re. A tension-induced fracture of the Mo/Re after the prior bend test showed a dimple fracture with a visible ductile core. Overall, the Mo/Re and W/Re alloys were suitable substrates for diamond growth. The Mo/Re alloy remained significantly more ductile than traditional tungsten substrates after diamond growth, and thus may be an attractive metal substrate for more ductile, thin-film diamond electrodes.

  14. Ductility minimum and its reversal with aging in cobalt-base superalloys

    International Nuclear Information System (INIS)

    Hammond, J.P.

    1979-01-01

    Good mechanical properties in the face of long-term aging at high temperatures are required of superalloys for nuclear and solar power-conversion applications. Of special concern are losses in ductility and toughness resulting from microstructural instability. The report compares the tensile ductility responses in two cobalt-base superalloys for the solution annealed and aged conditions and endeavors to rationalize results with contemporary concepts. The cobalt-base superalloys Haynes alloy No. 25 and Haynes alloy No. 188 show a pronounced ductility minimum at 760 0 C for the solution annealed condition. However, after prolonged (11,000 h) aging at 816 0 C, copious precipitates form and completely reverse this behavior. These precipitates drastically reduce tensile ductility up to the temperature at which the ductility begins to dip for the solution annealed condition; then the brittle behavior from aging gives way to greatly enhanced ductility. This behavior in Haynes alloy No. 25 was examined in detail. Tensile properties in the solution annealed and 816 0 C-aged conditions are correlated with mode of fracture and the amounts, identity, and morphology of the precipitates. The latter were assessed by optical and scanning electron metallography, microhardness, electron microprobe, and x-ray diffraction. The minimum and its reversal are explained by thermally activated processes that began with the onset of recovery

  15. Localized ductile deformation in the Rieserferner Pluton (Eastern Alps)

    Science.gov (United States)

    Ceccato, Alberto; Pennacchioni, Giorgio

    2017-04-01

    In the Rieserferner Pluton (Eastern Alps, 32±0.2 Ma, Romer et al., 2003) the post-magmatic cooling and exhumation stages were accompanied by a series of solid-state deformations including jointing, quartz veining, dyke emplacement, localized (cm-dm) ductile shearing and brittle-ductile faulting. The earliest stage of post-magmatic deformation includes the formation of pervasive steeply-dipping joints mainly arranged in two "conjugate" sets striking respectively E-W and NW-SE. These joints were extensively intruded by synkinematic aplite-pegmatite dykes and by quartz veins. Joints, veins and (locally) dikes were exploited as strike-slip ductile shear zones consistently with a WNW-ESE shortening. The mylonitized quartz veins are relatively coarse grained (mm-grain size) and show dominant dynamic recrystallization by grain boundary migration. A later set of joints is shallowly dipping E and is also commonly filled with quartz (and local epidote) veins. Ductile shearing of these vein-filled joints resulted in localized tonalite mylonites and quartz mylonites with a top-to-east kinematics. The quartz mylonites are fine grained (10-20 μm grain size) and resulted from dominant subgrain rotation recrystallization. The foliation of associated tonalite mylonites is marked by biotite+plagioclase+white mica+epidote±sphene±garnet. The "high-temperature" mylonites are crosscut by swarms of steeply-dipping fractures and faults striking N-S and showing a characteristic anastomosing-irregular pattern. These fractures are clustered in zones as large as 10 m and are associated with veins filled with calcite+white mica and with basic dykes (dated at 26 Ma: Steenken et al., 2000). Fluid-rock interactions along these fractures induced weakening and development of local low-temperature mylonites, where deformation mechanisms included pressure-solution and low-temperature plasticity of quartz. The orientation and kinematics of E-dipping mylonites and later low-temperature mylonites

  16. Ductility of aluminium alloy AA7075 at high strain rates

    Energy Technology Data Exchange (ETDEWEB)

    El-Magd, E.; Brodmann, M. [Technische Hochschule Aachen (Germany). Dept. of Mater. Sci.

    2000-09-01

    Under dynamic loading the stabilising effect of increased strain rate sensitivity of the material restrains neck formation in tension tests and leads to an increase in ductility. On the other hand the adiabatic character of the deformation process reduces the flow stress and promotes instability, localisation and adiabatic shear band initiation. Furthermore, the notch sensitivity of the material increases with increasing strain rate. Dynamic and quasi-static tension and compression tests were carried out on the age hardenable aluminium wrought alloy AA7075. There, dispers distributed precipitations are often the starting point for ductile fracture caused by impact due to the nucleation, growth and coalescence of voids and micro-cracks in case of tension. Neck formation under tensile loading and instabilities like shear bands in case of compression are discussed on the basis of the theory of imperfection under consideration of the increased strain rate sensitivity of the material and the adiabatic character of the deformation process at high strain rates. In case of tensile loading, tests with various notched geometries allowed the study of the influence of degree of multiaxiality. Through combination of experiment and simulation, the influence of strain rate on the local fracture strain could be determined for tensile and compression loading. (orig.)

  17. Influence of Microstructure on Strength and Ductility in Fully Pearlitic Steels

    Directory of Open Access Journals (Sweden)

    Jesús Toribio

    2016-12-01

    Full Text Available This article deals with the relationship between the microstructure and both strength and ductility in eutectoid pearlitic steel. It is seen how standard mechanical properties and fracture micromechanisms are affected by heat treatment and the resulting microstructure in the material. The yield stress, the ultimate tensile strength and the ductility (measured by means of the reduction in area exhibit a rising trend with the increasing cooling rate (associated with smaller pearlite interlamellar spacing and a lower pearlitic colony size, while the strain for maximum load shows a decreasing tendency with the afore-said rising cooling rate. With regard to the fracture surface, its appearance becomes more brittle for lower cooling rates, so that the fracture process zone exhibits a larger area with observable pearlite lamellae and a lower percentage of microvoids.

  18. Draft ASME code case on ductile cast iron for transport packaging

    Energy Technology Data Exchange (ETDEWEB)

    Saegusa, T. [Central Research Inst. of Electric Power Industry, Abiko (Japan); Arai, T. [Central Research Inst. of Electric Power Industry, Yokosuka (Japan); Hirose, M. [Nuclear Fuel Transport Co., Ltd., Tokyo (Japan); Kobayashi, T. [Nippon Chuzo, Kawasaki (Japan); Tezuka, Y. [Mitsubishi Materials Co., Tokyo (Japan); Urabe, N. [Kokan Keisoku K. K., Kawasaki (Japan); Hueggenberg, R. [GNB, Essen (Germany)

    2004-07-01

    The current Rules for Construction of ''Containment Systems for Storage and Transport Packagings of Spent Nuclear Fuel and High Level Radioactive Material and Waste'' of Division 3 in Section III of ASME Code (2001 Edition) does not include ductile cast iron in its list of materials permitted for use. The Rules specify required fracture toughness values of ferritic steel material for nominal wall thickness 5/8 to 12 inches (16 to 305 mm). New rule for ductile cast iron for transport packaging of which wall thickness is greater than 12 inches (305mm) is required.

  19. Relationships between fracture toughness and other material properties. Final report

    International Nuclear Information System (INIS)

    Perra, M.; Finnie, I.

    1974-01-01

    The key experimental and analytical studies which have led to our present understanding of the mechanisms of ductile fracture are reviewed. It is concluded that insufficient progress has been made in the quantitative description of ductile separation mechanisms on a microscale to allow the realistic prediction of fracture toughness from material properties and microstructure. An experimental study of ductile fracture is underway which has the aim of determining the growth rate of voids in known plastic deformation fields as a function of triaxiality of stress and material work-hardening. Novel specimens of particularly well characterized microstructure are utilized

  20. Size-Dependent Brittle-to-Ductile Transition in Silica Glass Nanofibers.

    Science.gov (United States)

    Luo, Junhang; Wang, Jiangwei; Bitzek, Erik; Huang, Jian Yu; Zheng, He; Tong, Limin; Yang, Qing; Li, Ju; Mao, Scott X

    2016-01-13

    Silica (SiO2) glass, an essential material in human civilization, possesses excellent formability near its glass-transition temperature (Tg > 1100 °C). However, bulk SiO2 glass is very brittle at room temperature. Here we show a surprising brittle-to-ductile transition of SiO2 glass nanofibers at room temperature as its diameter reduces below 18 nm, accompanied by ultrahigh fracture strength. Large tensile plastic elongation up to 18% can be achieved at low strain rate. The unexpected ductility is due to a free surface affected zone in the nanofibers, with enhanced ionic mobility compared to the bulk that improves ductility by producing more bond-switching events per irreversible bond loss under tensile stress. Our discovery is fundamentally important for understanding the damage tolerance of small-scale amorphous structures.

  1. Properties investigation of austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Sudhanshu Detwal

    2016-03-01

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

  2. Ductility of Ultra High Purity Copper

    OpenAIRE

    Fujiwara, S.; Abiko, K.

    1995-01-01

    The ductility of ultra-high purity copper at elevated temperatures was investigated : purity 99.9999% (6N) and 99.999999% (8N). Tensile tests were conducted at temperatures ranging from 293K to 1073K at strain rates of 4.2x10-5 s-1 in a high vacuum. The results are discussed in comparison with those for 99.9% (3N) copper. Ductility at intermediate temperatures was improved by an increase in purity. The temperature at which ductility dropped decreased with increases in purity. Even at the ultr...

  3. Development of small punch tests for ductile-brittle transition temperature measurement of temper embrittled Ni-Cr steels

    International Nuclear Information System (INIS)

    Baik, J.M.; Kameda, J.; Buck, O.

    1983-01-01

    Small punch tests were developed to determine the ductile-brittle transition temperature of nickel-chromium (Ni-Cr) steels having various degrees of temper embrittlement and various microstructures. It was found that the small punch test clearly shows the ductile-brittle transition behavior of the temper-embrittled steels. The measured values were compared with those obtained from Charpy impact and uniaxial tensile tests. The effects of punch tip shape, a notch, and the strain rate on the ductile-brittle transition behavior were examined. It was found that the combined use of a notch, high strain rates, and a small punch tip strongly affects the ductile-brittle transition behavior. Considerable variations in the data were observed when the small punch tests were performed on coarse-grained steels. Several factors controlling embrittlement measurements of steels are discussed in terms of brittle fracture mechanisms

  4. Thin Wall Austempered Ductile Iron (TWADI

    Directory of Open Access Journals (Sweden)

    M. Górny

    2009-07-01

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

  5. Austenitization of FerriticDuctile Iron

    Directory of Open Access Journals (Sweden)

    Krzyńska A.

    2014-12-01

    Full Text Available Austenitization is the first step of heat treatment preceding the isothermal quenching of ductile iron in austempered ductile iron (ADI manufacturing. Usually, the starting material for the ADI production is ductile iron with more convenient pearlitic matrix. In this paper we present the results of research concerning the austenitizing of ductile iron with ferritic matrix, where all carbon dissolved in austenite must come from graphite nodules. The scope of research includedcarrying out the process of austenitization at 900° Cusing a variable times ranging from 5 to 240minutes,and then observations of the microstructure of the samples after different austenitizing times. These were supplemented with micro-hardness testing. The research showed that the process of saturating austenite with carbon is limited by the rate of dissolution of carbon from nodular graphite precipitates

  6. Thin wall ductile and austempered iron castings

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2010-07-01

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

  7. Numerical simulations of material mismatch and ductile crack growth

    Energy Technology Data Exchange (ETDEWEB)

    Oestby, Erling

    2002-07-01

    Both the global geometry and inhomogeneities in material properties will influence the fracture behaviour of structures in presence of cracks. In this thesis numerical simulations have been used to investigate how some aspects of both these issues affect the conditions at the crack-tip. The thesis is organised in an introduction chapter, summarising the major findings and conclusions, a review chapter, presenting the main aspects of the developments in the field of fracture mechanics, and three research papers. Paper I considers the effect of mismatch in hardening exponent on the local near-tip stress field for stationary interface cracks in bi-materials under small scale yielding conditions. It is demonstrated that the stress level in the weaker material increases compared to what is found in the homogeneous material for the same globally applied load level, with the effect being of increasing importance as the crack-tip is approached. Although a coupling between the radial and angular dependence of the stress fields exists, the evolving stress field can still be normalised with the applied J. The effect on the increase in stress level can closely be characterised by the difference in hardening exponent, {delta}n, termed the hardening mismatch, and is more or less independent of the absolute level of hardening in the two materials. Paper II and Ill deal with the effects of geometry, specimen size, hardening level and yield stress mismatch in relation to ductile crack growth. The ductile crack growth is simulated through use of the Gurson model. In Paper H the effect of specimen size on the crack growth resistance is investigated for deep cracked bend and shallow cracked tensile specimens. At small amounts of crack growth the effect of specimen size on the crack growth resistance is small, but a more significant effect is found for larger amounts of crack growth. The crack growth resistance decreases in smaller specimens loaded in tension, whereas the opposite is

  8. Ductile and brittle transition behavior of titanium alloys in ultra-precision machining.

    Science.gov (United States)

    Yip, W S; To, S

    2018-03-02

    Titanium alloys are extensively applied in biomedical industries due to their excellent material properties. However, they are recognized as difficult to cut materials due to their low thermal conductivity, which induces a complexity to their deformation mechanisms and restricts precise productions. This paper presents a new observation about the removal regime of titanium alloys. The experimental results, including the chip formation, thrust force signal and surface profile, showed that there was a critical cutting distance to achieve better surface integrity of machined surface. The machined areas with better surface roughness were located before the clear transition point, defining as the ductile to brittle transition. The machined area at the brittle region displayed the fracture deformation which showed cracks on the surface edge. The relationship between depth of cut and the ductile to brittle transaction behavior of titanium alloys in ultra-precision machining(UPM) was also revealed in this study, it showed that the ductile to brittle transaction behavior of titanium alloys occurred mainly at relatively small depth of cut. The study firstly defines the ductile to brittle transition behavior of titanium alloys in UPM, contributing the information of ductile machining as an optimal machining condition for precise productions of titanium alloys.

  9. 46 CFR 56.60-15 - Ductile iron.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Ductile iron. 56.60-15 Section 56.60-15 Shipping COAST... Materials § 56.60-15 Ductile iron. (a) Ductile cast iron components made of material conforming to ASTM A... (incorporated by reference; see 46 CFR 56.01-2). (b) Ductile iron castings conforming to ASTM A 395...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-01-01

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

  11. Mechanisms for Ductile Rupture - FY16 ESC Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    Boyce, Brad L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Carroll, Jay D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Noell, Phillip [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bufford, Daniel Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Clark, Blythe G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hattar, Khalid Mikhiel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lim, Hojun [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Battaile, Corbett C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-01-01

    Ductile rupture in metals is generally a multi-step process of void nucleation, growth, and coalescence. Particle decohesion and particle fracture are generally invoked as the primary microstructural mechanisms for room-temperature void nucleation. However, because high-purity materials also fail by void nucleation and coalescence, other microstructural features must also act as sites for void nucleation. Early studies of void initiation in high-purity materials, which included post-mortem fracture surface characterization using scanning electron microscopy (SEM) and high-voltage electron microscopy (HVEM) and in-situ HVEM observations of fracture, established the presence of dislocation cell walls as void initiation sites in high-purity materials. Direct experimental evidence for this contention was obtained during in-situ HVEM tensile tests of Be single crystals. Voids between 0.2 and 1 μm long appeared suddenly along dislocation cell walls during tensile straining. However, subsequent attempts to replicate these results in other materials, particularly α -Fe single crystals, were unsuccessful because of the small size of the dislocation cells, and these remain the only published in-situ HVEM observations of void nucleation at dislocation cell walls in the absence of a growing macrocrack. Despite this challenge, other approaches to studying void nucleation in high-purity metals also indicate that dislocation cell walls are nucleation sites for voids.

  12. Ductile fracture behaviour of primary heat transport piping material ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Heat transport piping material of nuclear reactors. 169. Table 1. Chemical composition of. SA333, Grade 6 steel in wt%. C. Mn. Si. S. P. 0·18 0·90 0·25 0·02 0·02 room temperature. The tensile flow curve of the steel exhibited prominent yield-point effect accompanied by non-hardening strain propagation (Lüders strain) of ...

  13. Influence of ageing, inclusions and voids on ductile fracture ...

    Indian Academy of Sciences (India)

    Unknown

    adjacent particles limits the final dimple size to a value approximating to the average inter-particle spacing, as observed by Burghard (1974) as well as in the present investigation. Figure 5. Second-phase inclusion distribution in the commercial Al alloy: (a) optical micrograph and. (b) transmission electron micrograph.

  14. Ductile fracture behaviour of primary heat transport piping material ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    1. Introduction. The design of primary heat transport piping (PHT) of nuclear reactors has to ensure that uncontrolled failure does not occur under normal, faulted or accidental service conditions. One of the most severe failure scenarios traditionally envisaged is instantaneous double-ended guillotine break (DEGB), which ...

  15. Application of the load separation criterion in J-testing of ductile polymers: A round-robin testing exercise

    NARCIS (Netherlands)

    Agnelli, S.; Baldi, F.; Blackman, B.R.K.; Castellani, L.; Frontini, P.M.; Laiarinandrasana, L.; Pegoretti, A.; Rink, M.; Salazar, A.; Visser, Roy

    2015-01-01

    Round robin tests carried out under the direction of the Technical Committee 4 of the European Structural Integrity Society (ESIS TC4) have shown that, for determining the fracture resistance of ductile polymers at low loading rates, the multi-specimen methodology based on the construction of the

  16. A 3D ductile constitutive mixed-mode model of cohesive elements for the finite element analysis of adhesive joints

    DEFF Research Database (Denmark)

    Anyfantis, Konstantinos; Tsouvalis, Nicholas G.

    2013-01-01

    criterion and damage propagation with the linear energetic fracture criterion. For verification and validation purposes of the proposed laws and mixed-mode model, steel adherends have been adhesively bonded with a structural ductile adhesive material in order to fabricate a series of single and double strap...

  17. FATIGUE CRACK PROPAGATION THROUGH AUSTEMPERED DUCTILE IRON MICROSTRUCTURE

    Directory of Open Access Journals (Sweden)

    Lukáš Bubenko

    2010-10-01

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

  18. Strain Rate Dependent Ductile-to-Brittle Transition of Graphite Platelet Reinforced Vinyl Ester Nanocomposites

    Directory of Open Access Journals (Sweden)

    Brahmananda Pramanik

    2014-01-01

    Full Text Available In previous research, the fractal dimensions of fractured surfaces of vinyl ester based nanocomposites were estimated applying classical method on 3D digital microscopic images. The fracture energy and fracture toughness were obtained from fractal dimensions. A noteworthy observation, the strain rate dependent ductile-to-brittle transition of vinyl ester based nanocomposites, is reinvestigated in the current study. The candidate materials of xGnP (exfoliated graphite nanoplatelets reinforced and with additional CTBN (Carboxyl Terminated Butadiene Nitrile toughened vinyl ester based nanocomposites that are subjected to both quasi-static and high strain rate indirect tensile load using the traditional Brazilian test method. High-strain rate indirect tensile testing is performed with a modified Split-Hopkinson Pressure Bar (SHPB. Pristine vinyl ester shows ductile deformation under quasi-static loading and brittle failure when subjected to high-strain rate loading. This observation reconfirms the previous research findings on strain rate dependent ductile-to-brittle transition of this material system. Investigation of both quasi-static and dynamic indirect tensile test responses show the strain rate effect on the tensile strength and energy absorbing capacity of the candidate materials. Contribution of nanoreinforcement to the tensile properties is reported in this paper.

  19. Influence of specimen dimensions on ductile-to-brittle transition temperature in Charpy impact test

    Science.gov (United States)

    Rzepa, S.; Bucki, T.; Konopík, P.; Džugan, J.; Rund, M.; Procházka, R.

    2017-02-01

    This paper discusses the correlation between specimen dimensions and transition temperature. Notch toughness properties of Standard Charpy-V specimens are compared to samples with lower width (7.5 mm, 5 mm, 2.5 mm) and sub-size Charpy specimens with cross section 3×4. In this study transition curves are correlated with lateral ductile part of fracture related ones for 5 considered geometries. Based on the results obtained, correlation procedure for transition temperature determination of full size specimens defined by fracture appearance of sub-sized specimens is proposed.

  20. Ductilization of Cr via oxide dispersions

    International Nuclear Information System (INIS)

    Brady, M.P.; Wright, I.G.; Anderson, I.M.; Sikka, V.K.; Ohriner, E.K.; Walls, C.; Westmoreland, G.; Weaver, M.L.

    2001-01-01

    Work by Scruggs et al. in the 1960's demonstrated that up to 20 % tensile ductility could be achieved at room-temperature in sintered and extruded powder metallurgical Cr alloyed with MgO. During sintering, much of the MgO converts to a MgCr 2 O 4 spinel, which was hypothesized to getter nitrogen from the Cr, rendering it ductile. Recent efforts at Oak Ridge National Laboratory (ORNL) have succeeded in duplicating this original effect. Preliminary results suggest that the ductilization mechanism may be more complicated than the simple nitrogen gettering mechanism proposed by Scruggs, as some ductility was observed at room-temperature in Cr-MgO alloys containing nitride precipitates. Results of microstructural characterization and room-temperature mechanical property studies are presented for Cr-6MgO-(0-2.2) Ti wt.% as a function of hot-pressing and extrusion. Possible mechanisms by which the MgO additions may improve the room-temperature ductility of Cr are discussed. (author)

  1. Models for ductile crack initiation and tearing resistance under mode 1 loading in pressure vessel steels

    International Nuclear Information System (INIS)

    Jones, M.R.

    1988-06-01

    Micromechanistic models are presented which aim to predict plane strain ductile initiation toughness, tearing resistance and notched bar fracture strains in pressure vessel steels under monotonically increasing tensile (mode 1) loading. The models for initiation toughness and tearing resistance recognize that ductile fracture proceeds by the growth and linkage of voids with the crack-tip. The models are shown to predict the trend of initiation toughness with inclusion spacing/size ratio and can bound the available experimental data. The model for crack growth can reproduce the tearing resistance of a pressure vessel steel up to and just beyond crack growth initiation. The fracture strains of notched bars pulled in tension are shown to correspond to the achievement of a critical volume fraction of voids. This criterion is combined with the true stress - true strain history of a material point ahead of a blunting crack-tip to predict the initiation toughness. An attempt was made to predict the fracture strains of notched tensile bars by adopting a model which predicts the onset of a shear localization phenomenon. Fracture strains of the correct order are computed only if a ''secondary'' void nucleation event at carbide precipitates is taken into account. (author)

  2. Nose fracture

    Science.gov (United States)

    Fracture of the nose; Broken nose; Nasal fracture; Nasal bone fracture; Nasal septal fracture ... A fractured nose is the most common fracture of the face. It most ... occurs with other fractures of the face. Nose injuries and neck ...

  3. Cohesive traction–separation laws for tearing of ductile metal plates

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Hutchinson, John W.

    2012-01-01

    tip has advanced a distance of one or two plate thicknesses. Traction–separation laws are an essential component of finite element methods currently under development for analyzing fracture of large scale plate or shell structures. The present study resolves the sequence of failure details using...... to the tip. The objective of this paper is to analyze this sequential process to characterize the traction–separation behavior and the associated effective cohesive fracture energy of the entire failure process. The emphasis is on what is often described as plane stress behavior taking place after the crack...... the Gurson constitutive law based on the micromechanics of the ductile fracture process, including a recent extension that accounts for damage growth in shear. The fracture process in front of an advancing crack, subject to overall mode I loading, is approximated by a 2D plane strain finite element model...

  4. Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation.

    Science.gov (United States)

    Violay, M; Heap, M J; Acosta, M; Madonna, C

    2017-08-09

    Recently, projects have been proposed to engineer deep geothermal reservoirs in the ductile crust. To examine their feasibility, we performed high-temperature (up to 1000 °C), high-pressure (130 MPa) triaxial experiments on granite (initially-intact and shock-cooled samples) in which we measured the evolution of porosity during deformation. Mechanical data and post-mortem microstuctural characterisation (X-ray computed tomography and scanning electron microscopy) indicate that (1) the failure mode was brittle up to 900 °C (shear fracture formation) but ductile at 1000 °C (no strain localisation); (2) only deformation up to 800 °C was dilatant; (3) deformation at 900 °C was brittle but associated with net compaction due to an increase in the efficiency of crystal plastic processes; (4) ductile deformation at 1000 °C was compactant; (5) thermally-shocking the granite did not influence strength or failure mode. Our data show that, while brittle behaviour increases porosity, porosity loss is associated with both ductile behaviour and transitional behaviour as the failure mode evolves from brittle to ductile. Extrapolating our data to geological strain rates suggests that the brittle-ductile transition occurs at a temperature of 400 ± 100 °C, and is associated with the limit of fluid circulation in the deep continental crust.

  5. Recent development of ductile cast iron production technology in China

    Directory of Open Access Journals (Sweden)

    Cai Qizhou

    2008-05-01

    Full Text Available Recent progress in the production and technology of ductile cast iron castings in China is reviewed. The manufacture and process control of as-cast ductile iron are discussed. The microstructure, properties and application of partial austenitization normalizing ductile iron and austempered ductile iron (ADI are briefl y depicted. The new development of ductile iron production techniques, such as cored-wire injection (wire-feeding nodularization process, tundish cover ladle nodularizing process, horizontal continuous casting, and EPC process (lost foam for ductile iron castings, etc., are summarized.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-04-01

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

  7. Some mechanical properties of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-12-01

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

  8. Some Mechanical Properties of Austempered Ductile Iron

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-12-15

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

  9. Analysis of nucleation modelling in ductile cast iron

    DEFF Research Database (Denmark)

    Moumeni, Elham; Tutum, Cem Celal; Tiedje, Niels Skat

    2012-01-01

    Heterogeneous nucleation of nodular graphite at inclusions in ductile iron during eutectic solidification has been investigated. The experimental part of this work deals with casting of ductile iron samples with two different inoculants in four different thicknesses. Chemical analysis, metallogra...

  10. Deducing magnetic resonance neuroimages based on knowledge from samples.

    Science.gov (United States)

    Jiang, Yuwei; Liu, Feng; Fan, Mingxia; Li, Xuzhou; Zhao, Zhiyong; Zeng, Zhaoling; Wang, Yi; Xu, Dongrong

    2017-12-01

    Because individual variance always exists, using the same set of predetermined parameters for magnetic resonance imaging (MRI) may not be exactly suitable for each participant. We propose a knowledge-based method that can repair MRI data of undesired contrast as if a new scan were acquired using imaging parameters that had been individually optimized. The method employed a strategy called analogical reasoning to deduce voxel-wise relaxation properties using morphological and biological similarity. The proposed framework involves steps of intensity normalization, tissue segmentation, relaxation time deducing, and image deducing. This approach has been preliminarily validated using conventional MRI data at 3T from several examples, including 5 normal and 9 clinical datasets. It can effectively improve the contrast of real MRI data by deducing imaging data using optimized imaging parameters based on deduced relaxation properties. The statistics of deduced images shows a high correlation with real data that were actually collected using the same set of imaging parameters. The proposed method of deducing MRI data using knowledge of relaxation times alternatively provides a way of repairing MRI data of less optimal contrast. The method is also capable of optimizing an MRI protocol for individual participants, thereby realizing personalized MR imaging. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Interpretation and significance of reverse chevron-shaped markings on fracture surfaces of API X100 pipeline steels

    International Nuclear Information System (INIS)

    Sowards, Jeffrey W.; McCowan, Chris N.; Drexler, Elizabeth S.

    2012-01-01

    Highlights: ► We investigated fractures of X100 steel linepine produced during fracture mechanics testing. ► Fractures exhibited a unique chevron pattern that points in the direction of crack propagation. ► A qualitative model is proposed to explain the fracture pattern formation. ► Findings indicate that careful interpretation of ductile material fractures is necessary. - Abstract: Fracture surfaces of X100 pipeline steels were examined with optical and electron microscopy after crack tip opening angle fracture testing. Some fracture surfaces exhibited chevron-shaped fracture patterns that are markedly different from classic chevron fracture. The chevron-shaped markings on the X100 fracture surfaces point in the direction of crack growth, rather than towards the location of fracture initiation, as observed in classic cases of chevron fracture. Existing models, predicting formation of chevron fracture patterns, do not explain the fracture behavior observed for X100 steel. A mechanism is proposed where reverse chevron-shaped patterns are developed due to the shape of the crack front itself. The chevron shape forms as a result of crack tunneling, and the overall pattern is developed on the fracture surface due to intermittent crack growth, resulting in alternating regions (bands) of fast fracture and slower, more ductile fracture. The contrast between these bands of alternating fracture defines the chevron. Care should be taken during interpretation of intermittent chevron markings on fractures of ductile materials, as they may point away from rather than towards the origin of fracture.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-30

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

  13. Initiation of cleavage in a low alloy steel: effect of a ductile damage localized around inclusions; Declenchement du clivage dans un acier faiblement allie: role de l'endommagement ductile localise autour des inclusions

    Energy Technology Data Exchange (ETDEWEB)

    Carassou, S

    2000-07-01

    The fracture mechanism in a low alloy steel, used in the pressurised water reactor vessel, has been studied in the ductile to brittle transition temperature range. We used the local approach of fracture in conjunction with both fractographic observations and numerical simulations. Previous studies suggested the onset of cleavage to be favoured by the presence of nearby manganese sulphide (MnS) clusters: the ductile damaged zone localised inside a cluster increases the stress around it, and so contribute to the triggering of cleavage due to nearby classical sites, like carbides. The experimental study of size dependence and anisotropy on the global fracture behaviour, together with fractographic observations, give here the proof of the influence of MnS clusters on the onset of cleavage in this steel. Fracture behaviour of pre-cracked specimens tested in the transition regime has then been simulated, by three dimensional finite element method computations. Ductile tearing process preceding the cleavage onset at those temperatures regime was well reproduced by the Rousselier's model. Failure probabilities, related to given stress states, has been given by post-processor calculations, using a probabilistic model based on the specific cleavage fracture process. Fracture toughness scatter of the steel, tested in the transition regime, is then well reproduced by those calculations. However, the critical cleavage stress of an elementary volume, that scales for the fracture process, is still assumed to be temperature dependant. Numerical simulations of the local fracture process suggest that this temperature effect can partly be explained by the temperature dependant decrease of the stress amplification due to the MnS clusters. (author)

  14. Effect of Bi on graphite morphology and mechanical properties of heavy section ductile cast iron

    Directory of Open Access Journals (Sweden)

    Song Liang

    2014-03-01

    Full Text Available To improve the mechanical properties of heavy section ductile cast iron, bismuth (Bi was introduced into the iron. Five castings with different Bi content from 0 to 0.014 wt.% were prepared; and four positions in the casting from the edge to the center, with different solidification cooling rates, were chosen for microstructure observation and mechanical properties test. The effect of the Bi content on the graphite morphology and mechanical properties of heavy section ductile cast iron were investigated. Results show that the tensile strength, elongation and impact toughness at different positions in the five castings decrease with a decrease in cooling rate. With an increase in Bi content, the graphite morphology and the mechanical properties at the same position are improved, and the improvement of mechanical properties is obvious when the Bi content is no higher than 0.011wt.%. But when the Bi content is further increased to 0.014wt.%, the improvement of mechanical properties is not obvious due to the increase of chunky graphite number and the aggregation of chunky graphite. With an increase in Bi content, the tensile fracture mechanism is changed from brittle to mixture ductile-brittle fracture.

  15. Calculation Method of Lateral Strengths and Ductility Factors of Constructions with Shear Walls of Different Ductility

    Science.gov (United States)

    Yamaguchi, Nobuyoshi; Nakao, Masato; Murakami, Masahide; Miyazawa, Kenji

    2008-07-01

    For seismic design, ductility-related force modification factors are named R factor in Uniform Building Code of U.S, q factor in Euro Code 8 and Ds (inverse of R) factor in Japanese Building Code. These ductility-related force modification factors for each type of shear elements are appeared in those codes. Some constructions use various types of shear walls that have different ductility, especially for their retrofit or re-strengthening. In these cases, engineers puzzle the decision of force modification factors of the constructions. Solving this problem, new method to calculate lateral strengths of stories for simple shear wall systems is proposed and named `Stiffness—Potential Energy Addition Method' in this paper. This method uses two design lateral strengths for each type of shear walls in damage limit state and safety limit state. Two lateral strengths of stories in both limit states are calculated from these two design lateral strengths for each type of shear walls in both limit states. Calculated strengths have the same quality as values obtained by strength addition method using many steps of load-deformation data of shear walls. The new method to calculate ductility factors is also proposed in this paper. This method is based on the new method to calculate lateral strengths of stories. This method can solve the problem to obtain ductility factors of stories with shear walls of different ductility.

  16. Finite pure integer programming algorithms employing only hyperspherically deduced cuts

    Science.gov (United States)

    Young, R. D.

    1971-01-01

    Three algorithms are developed that may be based exclusively on hyperspherically deduced cuts. The algorithms only apply, therefore, to problems structured so that these cuts are valid. The algorithms are shown to be finite.

  17. Fracture Mechanics

    International Nuclear Information System (INIS)

    Jang, Dong Il; Jeong, Gyeong Seop; Han, Min Gu

    1992-08-01

    This book introduces basic theory and analytical solution of fracture mechanics, linear fracture mechanics, non-linear fracture mechanics, dynamic fracture mechanics, environmental fracture and fatigue fracture, application on design fracture mechanics, application on analysis of structural safety, engineering approach method on fracture mechanics, stochastic fracture mechanics, numerical analysis code and fracture toughness test and fracture toughness data. It gives descriptions of fracture mechanics to theory and analysis from application of engineering.

  18. A practical method for computation of ductile crack growth by means of finite elements and parametric 3D-modelling

    International Nuclear Information System (INIS)

    Baumjohann, F.; Kroening, J.

    1999-01-01

    The present paper originates from a contribution to the safety assessment of a reactor pressure vessel (RPV). Investigations evaluating the safety against brittle fracture (exclosure of crack initiation and arrest assessments) are completed by calculations concerning ductile crack extension. Crack geometries including the expected crack extension are generated parametrically by a computer code and are used for further calculations with finite element programs. J-integrals of ductile growing cracks located between two comparative contours are determined by interpolation. The comparative contours are loaded by instationary temperature and pressure fields and are evaluated in advance. Taking the stability condition into consideration, the ductile crack extension is determined by pursuing the equilibrium between loading and crack resistance. The automatic modelling and a mathematical program processing the finite element results evaluate the crack growth of the finite element results very effectively. (orig.)

  19. Application of microstatistical fracture mechanics to dynamic fracture problems

    International Nuclear Information System (INIS)

    Shockey, D.A.; Curran, D.R.; Seaman, L.

    1983-01-01

    This chapter presents a microstatistical treatment of shear bands. Describes the microstatistical fracture mechanics (MSFM) approach by illustrating its use in the case of shock-induced ductile voids in steel. Shows that the microstatistical approach merges with the continuum approach. Computes the behavior of a macrocrack propagating in a DCB specimen by using MSFM and the data generated in the shock wave experiments. Discusses shockwave-induced ductile fractures; plate impact experiments; data analysis; progress in MSFM and required research efforts; and macrocrack propagation. Points out that although continuum treatments have the advantage of simplicity and low cost, the more complex and expensive MSFM treatment may be the only viable approach when detailed information is needed such as size, velocity, and trajectory distributions of fragments ejected from a plate of armor steel after impact

  20. Stacking faults in austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-06-01

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

  1. Modelling of the effect of precipitates on work-hardening, ductility and impact behaviour of ferritic-martensitic Cr steels

    Science.gov (United States)

    Preininger, D.

    2002-12-01

    The effect of precipitates on work-hardening, tensile ductility and impact behaviour of carbon and high nitrogen martensitic 7-12Cr as well as particle strengthened ODS-(9-13)Cr steels have been analysed by models. A minimum of work-hardening and uniform strain generally appears around 600 °C at onset of dislocation recovery. Pronounced precipitation by increasing nitrogen and carbon content or additionally of fine Y 2O 3-particles distinctly increases work-hardening and uniform ductility. These, however, decrease with increasing strengthening but do not reach a visible level above 1500 MPa for ODS-steels at 20 °C. Minima of total elongation and fracture strain additionally appear in carbon and nitrogen martensitic steels around 300 °C where dynamic strain ageing occurs. Fracture strain and ductile upper shelf energy of Charpy tests in accordance with model predictions also decrease with increasing yield strength more strongly for ODS-steels due to their enhanced work-hardening and localized deformation. The strength-induced increase of ductile-to-brittle transition temperatures of ODS-steels is comparable to that observed by irradiation defect strengthening.

  2. Failure by fracture in bulk metal forming

    DEFF Research Database (Denmark)

    Silva, C.M.A.; Alves, Luis M.; Nielsen, Chris Valentin

    2015-01-01

    This paper revisits formability in bulk metal forming in the light of fundamental concepts of plasticity,ductile damage and crack opening modes. It proposes a new test to appraise the accuracy, reliability and validity of fracture loci associated with crack opening by tension and out-of-plane shear...

  3. The effect of pearlite on the hydrogen-induced ductility loss in ductile cast irons

    Science.gov (United States)

    Matsuo, T.

    2017-05-01

    Hydrogen energy systems, such as a hydrogen fuel cell vehicle and a hydrogen station, are rapidly developing to solve global environmental problems and resource problems. The available structural materials used for hydrogen equipments have been limited to only a few relatively expensive metallic materials that are tolerant for hydrogen embrittlement. Therefore, for the realization of a hydrogen society, it is important to expand the range of materials available for hydrogen equipment and thereby to enable the use of inexpensive common materials. Therefore, ductile cast iron was, in this study, focused as a structural material that could contribute to cost reduction of hydrogen equipment, because it is a low-cost material having good mechanical property comparable to carbon steels in addition to good castability and machinability. The strength and ductility of common ductile cast irons with a ferritic-pearlitic matrix can be controlled by the volume fraction of pearlitic phase. In the case of carbon steels, the susceptibility to hydrogen embrittlement increases with increase in the pearlite fraction. Toward the development of ferritic-pearlitic ductile cast iron with reasonable strength for hydrogen equipment, it is necessary to figure out the effect of pearlite on the hydrogen embrittlement of this cast iron. In this study, the tensile tests were conducted using hydrogen-precharged specimens of three kinds of ferritic-pearlitic ductile cast irons, JIS-FCD400, JIS-FCD450 and JIS-FCD700. Based on the results, the role of pearlite in characterizing the hydrogen embrittlement of ductile cast iron was discussed.

  4. Ductile damage development in friction stir welded aluminum (AA2024) joints

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau

    2008-01-01

    Ductile damage development in a friction stir welded aluminum joint subjected to tension is analyzed numerically by FE-analysis, based on a total Lagrangian formulation. An elastic-viscoplastic constitutive relation that accounts for nucleation and growth of microvoids is applied. Main focus...... in the paper is on the interaction between changes in the material parameters in different regions of the weld, the damage development and the position of the final fracture. Especially changes in the yield stress profile transverse to the weldline are examined, since some process parameters have been shown...

  5. Influence of sulphur and phosphorus impurities on ductility of 25Kh2NMFA steel during forging

    International Nuclear Information System (INIS)

    Onishchenko, A.K.

    1989-01-01

    Using cylindrical samples of the 25Kh2NMFA steel with sulfur and phosphorus content in the range of 0.001-0.030%, tensile test with the rate of deformation 10 -3 s -1 at the temperatures of 800-1200 deg C has been conducted. Analysis of fracture foci and plasticity diagrams has shown, that to ensure ductility during forging and high mechanical properties, the content of sulfur and phosphorus impurities in the 25Kh2NMFA steel must not exceed 0.015%

  6. Study on the structural integrity of a PWR vessel according to the ductile cracking instability theory

    International Nuclear Information System (INIS)

    Tarpani, Jose Ricardo; Spinelli, Dirceu

    1996-01-01

    Analytical predictions of PWR vessel instability have been made according to Linear Elastic criterion K lC and Elastic-Plastic Fracture Mechanics Ji, J 50 and J inst . Special attention was given to the influence of crack depth and length on both approaches, as well as to the data extrapolation procedures on elasto-plasticity. Simple and didactic format has been supplied for the results evaluation in terms of internal pressure, wall-through strain gradient and ductile stable crack extension. (author)

  7. Low ductility creep failure in austenitic weld metals

    International Nuclear Information System (INIS)

    Thomas, R.G.

    Creep tests have been carried out for times of up to approx. 22,000 hrs on three austenitic weld metals of nominal composition 17Cr-8Ni-2Mo, 19Cr-12Ni-3Mo+Nb and 17Cr-10Ni-2Mo. The two former deposits were designed to produce delta-ferrite contents in the range 3-9% while the latter was designed to be fully austenitic. The common feature of all three weld metals was that they all gave very low strains at failure, typically approx. 1%. The microstructures of the failed creep specimens have been studied using optical and electron microscopy and the precipitate structures related to the occurrence of low creep strains. Creep deformation and fracture mechanisms in austenitic materials in general have been reviewed and this has been used as a basis for discussion of the observations of the present work. Finally, some of the factors that can be controlled to improve long-term creep ductility have been appraised

  8. Comparison of ductile-to-brittle transition curve fitting approaches

    International Nuclear Information System (INIS)

    Cao, L.W.; Wu, S.J.; Flewitt, P.E.J.

    2012-01-01

    Ductile-to-brittle transition (DBT) curve fitting approaches are compared over the transition temperature range for reactor pressure vessel steels with different kinds of data, including Charpy-V notch impact energy data and fracture toughness data. Three DBT curve fitting methods have been frequently used in the past, including the Burr S-Weibull and tanh distributions. In general there is greater scatter associated with test data obtained within the transition region. Therefore these methods give results with different accuracies, especially when fitting to small quantities of data. The comparison shows that the Burr distribution and tanh distribution can almost equally fit well distributed and large data sets extending across the test temperature range to include the upper and lower shelves. The S-Weibull distribution fit is poor for the lower shelf of the DBT curve. Overall for both large and small quantities of measured data the Burr distribution provides the best description. - Highlights: ► Burr distribution offers a better fit than that of a S-Weibull and tanh fit. ► Burr and tanh methods show similar fitting ability for a large data set. ► Burr method can fit sparse data well distributed across the test temperature. ► S-Weibull method cannot fit the lower shelf well and show poor fitting quality.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-07-01

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

  10. Ductile alloys for sealing modular component interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Marra, John J.; Wessell, Brian J.; James, Allister W.; Marsh, Jan H.; Gear, Paul J.

    2017-08-08

    A vane assembly (10) having: an airfoil (12) and a shroud (14) held together without metallurgical bonding there between; a channel (22) disposed circumferentially about the airfoil (12), between the airfoil (12) and the shroud (14); and a seal (20) disposed in the channel (22), wherein during operation of a turbine engine having the vane assembly (10) the seal (20) has a sufficient ductility such that a force generated on the seal (20) resulting from relative movement of the airfoil (12) and the shroud (14) is sufficient to plastically deform the seal (20).

  11. Influence of Ti on the Hot Ductility of High-manganese Austenitic Steels

    Science.gov (United States)

    Liu, Hongbo; Liu, Jianhua; Wu, Bowei; Su, Xiaofeng; Li, Shiqi; Ding, Hao

    2017-07-01

    The influence of Ti addition ( 0.10 wt%) on hot ductility of as-cast high-manganese austenitic steels has been examined over the temperature range 650-1,250 °C under a constant strain rate of 10-3 s-1 using Gleeble3500 thermal simulation testing machine. The fracture surfaces and particles precipitated at different tensile temperatures were characterized by means of scanning electron microscope and X-ray energy dispersive spectrometry (SEM-EDS). Hot ductility as a function of reduction curves shows that adding 0.10 wt% Ti made the ductility worse in the almost entire range of testing temperatures. The phases' equilibrium diagrams of precipitates in Ti-bearing high-Mn austenitic steel were calculated by the Thermo-Calc software. The calculation result shows that 0.1 wt% Ti addition would cause Ti(C,N) precipitated at 1,499 °C, which is higher than the liquidus temperature of high-Mn austenitic steel. It indicated that Ti(C,N) particles start forming in the liquid high-Mn austenitic steel. The SEM-EDS results show that Ti(C,N) and TiC particles could be found along the austenite grain boundaries or at triple junction, and they would accelerate the extension of the cracks along the grain boundaries.

  12. Modelling the Fracture Behavior of a 350WT Steel

    Science.gov (United States)

    2014-05-01

    of the pendulum after fracturing the specimen. Figure 4.1: Charpy V-Notch Specimen, Anvil Supports and Striker [9] Modelling the Fracture Behavior of...determined through FE calibration with existing Charpy V-notch (CVN) and dynamic tear ductile-to-brittle transition (DBT) data. Once the parameters...8 4.0 DETERMINATION OF FRACTURE PARAMETERS..........................................................................11 4.1 CHARPY V-NOTCH

  13. Growth patterns of fossil vertebrates as deduced from bone

    Indian Academy of Sciences (India)

    2009-10-20

    Oct 20, 2009 ... Growth patterns of fossil vertebrates as deduced from bone microstructure: case studies from India ... https://www.ias.ac.in/article/fulltext/jbsc/034/05/0661-0672 ... A comparative study encompassing several neotherapsid genera including the dicynodonts shows significant evolutionary trends towards ...

  14. Deducing Reaction Mechanism: A Guide for Students, Researchers, and Instructors

    Science.gov (United States)

    Meek, Simon J.; Pitman, Catherine L.; Miller, Alexander J. M.

    2016-01-01

    An introductory guide to deducing the mechanism of chemical reactions is presented. Following a typical workflow for probing reaction mechanism, the guide introduces a wide range of kinetic and mechanistic tools. In addition to serving as a broad introduction to mechanistic analysis for students and researchers, the guide has also been used by…

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

    Directory of Open Access Journals (Sweden)

    Gong Wenbang

    2012-05-01

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

  16. Effect of Melting Techniques on Ductile Iron castings Properties

    Directory of Open Access Journals (Sweden)

    Bockus, S.

    2006-01-01

    Full Text Available The study was designed to investigate the effects of the charge, melting conditions, nodularizing and inoculation on the ductile iron castings properties. Results showed that the temperature and holding time of the melt in an induction furnace and the intensity of spheroidizing effect on the carbon and residual magnesium contents in the ductile iron castings. The same grade of ductile iron may be obtained using different chemical compositions. The castings of ductile iron will be ferritic as-cast only when large amount of pig iron in the charge and in addition some-steps inoculating treatment are used.

  17. System Reliability of Timber Structures with Ductile Behaviour

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Čizmar, Dean

    2011-01-01

    . An evaluation method of the ductile behaviour is introduced. For different ductile behaviours, the system reliability is estimated based on Monte Carlo simulation. A correlation between the strength of the structural elements is introduced. The results indicate that the reliability of a structural timber system......The present paper considers the evaluation of timber structures with the focus on robustness due to connection ductility. The robustness analysis is based on the structural reliability framework applied to a simplified mechanical system. The structural timber system is depicted as a parallel system...... can be significantly increased due to the ductile behavior....

  18. Micromechanical prediction of fracture toughness for pressure vessel steel using a coupled model

    International Nuclear Information System (INIS)

    Goldthorpe, M.R.; Wiesner, C.S.

    1999-01-01

    Ferritic components in nuclear plant should ideally operate on the upper shelf of the ductile to brittle transition curve describing the variation of material toughness with temperature. A method of analyzing the ductile to brittle transition region of a ferritic steel using a coupled micromechanical model of ductile damage, stable crack growth and cleavage fracture has been developed to improve the definition of upper shelf behavior for actual structures. Ductile damage is modelled using the Gurson model as modified by Tvergaard, along with a specially developed crack growth user element. The probability of cleavage fracture is predicted by post-processing the finite element results using the Beremin model of cleavage fracture. Predictions are made of ductile tearing and cleavage fracture in test specimen and wide plate configurations of A533B steel for a range of temperatures. The coupled model is capable of predicting transition toughness and transition temperature shifts for different levels of structural constraint. An analytically-based definition of the onset of upper shelf temperature (OUST) is the temperature at which the coupled ductile damage/cleavage fracture model predicts a probability of failure by cleavage fracture of 5%. Estimates of the shift in the OUST due to different levels of in-plane crack tip constraint are made using the elastic T-stress as a measure of constraint. There is potential for using the T-stress as a measure of structural constraint in order to determine shifts in transition temperature for materials with degraded toughness

  19. Fracture Mechanics of Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, Jens Peder

    Since analytical methods are very time consuming different analytical models have been developed. Three methods for plain concrete are presented, where one of the methods is developed by the author. The method is based on three different fracture models. Also two models applicable for lightly reinforced...... with a description of the different types of size effects. Three examples which discuss the two terms 'size effect' and 'brittleness' and the importance of a stiff test rig. Finally some brittleness numbers are defined. Chapter 3 In chapter 3 the most well-known numerical methods which use the fictitious crack...... to describe fracture in concrete are presented. Two of the methods are combined into a power method which is stable for all brittleness numbers and which is able of calculating the entire load-displacement curve even for very ductile beams. This method is used extensively in the rest of the thesis. Chapter 4...

  20. Deformation Behavior of Ultra-Strong and Ductile Mg-Gd-Y-Zn-Zr Alloy with Bimodal Microstructure

    Science.gov (United States)

    Xu, C.; Fan, G. H.; Nakata, T.; Liang, X.; Chi, Y. Q.; Qiao, X. G.; Cao, G. J.; Zhang, T. T.; Huang, M.; Miao, K. S.; Zheng, M. Y.; Kamado, S.; Xie, H. L.

    2018-02-01

    An ultra-strong and ductile Mg-8.2Gd-3.8Y-1Zn-0.4Zr (wt pct) alloy was developed by using hot extrusion to modify the microstructure via forced-air cooling and an artificial aging treatment. A superior strength-ductility balance was obtained that had a tensile yield strength of 466 MPa and an elongation to failure of 14.5 pct. The local strain evolution during the in situ testing of the ultra-strong and ductile alloy was quantitatively analyzed with high-resolution electron backscattered diffraction and digital image correlation. The fracture behavior during the tensile test was characterized by synchrotron X-ray tomography along with SEM and STEM observations. The alloy showed a bimodal microstructure, consisting of dynamically recrystallized (DRXed) grains with random orientations and elongated hot-worked grains with parallel to the extrusion direction. The DRXed grains were deformed by the basal slip and the hot-worked grains were deformed by the prismatic slip dominantly. The strain evolution analysis indicated that the multilayered structure relaxed the strain localization via strain transfer from the DRXed to the hot-worked regions, which led to the high ductility of the alloy. Precipitation of the γ' on basal planes and the β' phases on the prismatic planes of the α-Mg generated closed volumes, which enhanced the strength by pinning dislocations effectively, and contributed to the high ductility by impeding the propagation of micro-cracks inside the grains. The deformation incompatibility between the hot-worked grains and the arched block-shaped long-period stacking ordered (LPSO) phases induced the crack initiation and propagation, which fractured the alloy.

  1. Wear resistance properties of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Lerner, Y.S. [Univ. of Northern Iowa, Cedar Falls, IA (United States); Kingsbury, G.R. [Kingsbury (G.R.), Lyndhurst, OH (United States)

    1998-02-01

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

  2. SiMo Ductile Iron Crystallization Process

    Directory of Open Access Journals (Sweden)

    Stawarz M.

    2017-03-01

    Full Text Available The article presents crystallization process of silicon molybdenum ductile cast iron (SiMo. The alloy with 5% silicon content and with variable amounts of Mo in a range of 0-1% was chosen for the research. The carbon content in the analysed alloys did not exceed 3,1%. The studies of crystallization process were based on thermal - derivative analysis (TDA. Chemical composition of all examined samples was analysed with the use of LECO spectrometer. Additionally, the carbon and the sulphur content was determined basing on carbon and sulphur LECO analyser. For metallographic examination, the scanning electron microscopy (SEM with EDS analyser was used. Disclosed phases have been also tested with the use of X-ray diffraction. The results allowed the description of crystallization processes of silicon molybdenum ductile cast iron using thermal - derivative analysis (TDA. Conducted studies did not allow for the clear identification of all complex phases containing molybdenum, occurring at the grain boundaries. Therefore, the further stages of the research could include the use of a transmission electron microscope to specify the description of complex compounds present in the alloy.

  3. Reconstituted Keratin Biomaterial with Enhanced Ductility

    Directory of Open Access Journals (Sweden)

    Halleh Atri

    2015-11-01

    Full Text Available Nowadays the waste from protein fibres represents an important renewable source for a new generation of biomaterials and promising competitors for carbohydrate based biomaterials. Regenerated keratin biomaterials are biodegradable in vivo and in vitro, biocompatible, and support cell attachment and proliferation; however, their major drawback has been their weak mechanical properties such as ductility. The following study was conducted in an attempt to improve the ductility of reconstituted keratin films obtained from Australian merino wool fibres. Keratin was extracted from wool fibres according to an established protocol proposed by Yamauchi, and then dialyzed and desalted by multiple diafiltration wash cycles. The resulting keratin film was transparent, biodegradable, and, opposite to its predecessors, mechanically durable, possessing a Young modulus about 12.5 MPa with 35% extensibility. The polypeptide chains were found to rearrange themselves in the β-sheet state in this keratin film, which was shown to be semi-crystalline. This film, unlike its predecessors, did not support human cell proliferation. These properties of the diafiltered keratin film have led us to think that diafiltration resulted in producing a totally new keratin film, which is envisaged to find applications in various areas.

  4. Overview of Intergranular Fracture of Neutron Irradiated Austenitic Stainless Steels

    Directory of Open Access Journals (Sweden)

    Anna Hojná

    2017-09-01

    Full Text Available Austenitic stainless steels are normally ductile and exhibit deep dimples on fracture surfaces. These steels can, however, exhibit brittle intergranular fracture under some circumstances. The occurrence of intergranular fracture in the irradiated steels is briefly reviewed based on limited literature data. The data are sorted according to the irradiation temperature. Intergranular fracture may occur in association with a high irradiation temperature and void swelling. At low irradiation temperature, the steels can exhibit intergranular fracture at low or even at room temperatures during loading in air and in high temperature water (~300 °C. This paper deals with the similarities and differences for IG fractures and discusses the mechanisms involved. The intergranular fracture occurrence at low temperatures might be correlated with decohesion or twinning and strain martensite transformation in local narrow areas around grain boundaries. The possibility of a ductile-to-brittle transition is also discussed. In case of void swelling higher than 3%, quasi-cleavage at low temperature might be expected as a consequence of ductile-to-brittle fracture changes with temperature. Any existence of the change in fracture behavior in the steels of present thermal reactor internals with increasing irradiation dose should be clearly proven or disproven. Further studies to clarify the mechanism are recommended.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-09-01

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

  6. COMPUTER MODELING OF STRAINS ON PHASE BOUNDARIES IN DUCTILE CAST IRON AT HOT EXTRUSION

    Directory of Open Access Journals (Sweden)

    A. I. Pokrovsky

    2017-01-01

    Full Text Available The computer modeling of the strain distribution in the structure of ductile iron with ferrite-pearlite matrix and inclusions of spherical graphite dependence on increasing degree of deformation during direct hot extrusion was researched. Using a software system of finite-element analysis ANSYS the numerical values of the strains at the phase boundaries: ferrite-perlite, graphiteferrite and also inside the graphite inclusions were defined. The analysis of the strain distribution in the investigated structures was performed and local zones of increased strains were discovered. The results of modeling are compared with metallographic analysis and fracture patterns. The obtained results could be used in the prediction of fracture zones in the cast iron products. 

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

    Science.gov (United States)

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

    2016-03-01

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

  8. Transformation plasticity in ductile solids. Annual progress report, June 1, 1992--May 31, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Olson, G.B.

    1993-02-01

    Research has addressed the role of martensitic transformation plasticity in the enhancement of toughness in high-strength austenitic steels, and the enhancement of formability in multiphase low-alloy sheet steels. In the austenitic steels, optimal processing conditions have been established to achieve a significant increase in strength level, in order to investigate the interaction of strain-induced transformation with the microvoid nucleation and shear localization mechanisms operating at ultrahigh strength levels. The stress-state dependence of transformation and fracture mechanisms has been investigated in model alloys, comparing behavior in uniaxial tension and blunt-notch tension specimens. A numerical constitutive model for transformation plasticity has been reformulated to allow a more thorough analysis of transformation/fracture interactions. Processing of a new low alloy steel composition has been optimized to stabilize retained austenite by isothermal bainitic transformation after intercritical annealing. Preliminary results show a good correlation of uniform ductility with the austenite amount and stability.

  9. The fracture of ordered (Fe, Co)3V

    International Nuclear Information System (INIS)

    Liu, C.T.; Schulson, E.M.

    1984-01-01

    Observations have been made of fracture surfaces deformed at low strain rates (3.3 and 42 X 10 -3 S -1 ) in tension at temperatures from 20 to 1000 0 C, that is, above and below the order/disorder transformation temperature of 950 + or - 10 0 C. From 20 to 700 0 C, transgranular fracture occurs via the nucleation, growth, and coalescence of microvoids; high ductilities are obtained (34 to 44 pct). From 700 to 960 0 C, the fracture mode changes from transgranular to intergranular and ductility falls to a minimum of 4 pct. At 1000 0 C a third mode operates consisting of localized dynamic recrystallization followed by boundary sliding of recrystallized grains; ductility rises sharply. The underlying mechanisms are supported through additional experiments performed at higher strain rates

  10. The effect of specimen size on the ductile/brittle transition temperature in an A533B pressure vessel steel

    International Nuclear Information System (INIS)

    Green, G.; Knott, J.F.

    It was ascertained that it is possible to relate critical crack opening displacement (COD) values, deltasub(crit), obtained on small specimens of A 533-B pressure vessel steel to the fracture toughness value representing the initiation of fracture in a large structure. The variation of deltasub(crit) with temperature is given. A sharp increase in deltasub(crit) is observed above a temperature of approximately -100 degC and this was found to be associated with the initiation of small amounts of fibrous fracture, prior to a cleavage instability. An upper limit to the deltasub(crit) values was obtained above -50 degC, where the fracture was found to be fully ductile. Values of deltasub(crit) estimated from the valid fracture toughness results are shown for comparison. At low temperatures the estimated deltasub(crit) values are seen to be less than those measured in the small bend specimens and the sharp increase in the estimated deltasub(crit) values occurs at a higher temperature, approximately 0 degC. The room temperature deltasub(crit) value, estimated from the valid toughness results (0.15 mm) compares well with COD for the initiation of fibrous fracture, measured at the same temperature in small bend specimens (0.175 mm). The following conclusions were drawn from the experiments: 1. The ductile/brittle transition temperature, determined by critical COD measurements, is influenced by the relaxation of triaxial stresses in small specimens. 2. It is possible to relate critical COD values for the initiation of fibrous fracture, measured in small specimens, to the fracture toughness representing this behaviour in a large structure

  11. Current Issues on Hydride Effects of Zr-base Cladding Tube on the Ductility in RIA simulating Tests

    International Nuclear Information System (INIS)

    Kim, Sunki; Bang, Jegeon; Lee, Chanbock; Kim, Daeho; Yang, Yongsik

    2006-01-01

    During operation in nuclear reactor the cladding tube forms a hydride rim that resides above a substrate that is relatively free of hydrides. A prediction of the ductility of such cladding tubes must take into account: the density of the hydrides as a layer/rim and the rim thickness, the ability of the hydrides to deform, their circumferential orientation within the layer, and the presence of a relatively unhydrided substrate. Recent experiments based on unirradiated cladding tubes containing hydrides in the form of a rim indicate a significant loss of ductility with (a) increasing hydrogen content and/or (b) increasing hydride rim thicknesses. These results suggest that a ductile-to brittle transition occurs with increasing hydride rim thickness. Since the hydride rim initiates a crack early in the deformation process, fracture mechanics has been recently used to predict failure on the basis of crack propagation. While this type of analysis can be applied to brittle cladding with thick hydride rims, failure of cladding with small- thickness hydride rims exhibits significant ductility; importantly, this cladding does not appear to obey fracture mechanics, as the fracture stress approaches the tensile strength of the cladding. To provide a data base for the regulatory guide of light water reactors, behavior of reactor fuels during off normal and postulated accident conditions such as reactivity-initiated accident (RIA) has been studied in the Nuclear Safety Research Reactor (NSRR) program in Japan. A series of experiments with high burnup fuel rods were performed by using pulse irradiation capability of the NSRR. This paper presents recent results obtained from the NSRR power burst experiments with irradiated PWR fuels with ZIRLOTM and MDA (Mitsubishi Developed Alloy, Zr-0.8Sn- 0.2Fe-0.1Cr-0.5Nb) claddings, and discusses effects of pellet expansion as PCMI (Pellet-Cladding Mechanical Interaction) loading and cladding embrittlement primarily due to hydrogen

  12. DUCTILE-PHASE TOUGHENED TUNGSTEN FOR PLASMA-FACING MATERIALS IN FUSION REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Henager, Charles H.; Setyawan, Wahyu; Roosendaal, Timothy J.; Overman, Nicole R.; Borlaug, Brennan A.; Stevens, Erica L.; Wagner, Karla B.; Kurtz, Richard J.; Odette, G Robert; Nguyen, Ba Nghiep; Cunningham, Kevin

    2017-05-01

    Tungsten (W) and W-alloys are the leading candidates for plasma-facing components in nuclear fusion reactor designs because of their high melting point, strength retention at high temperatures, high thermal conductivity, and low sputtering yield. However, tungsten is brittle and does not exhibit the required fracture toughness for licensing in nuclear applications. A promising approach to increasing fracture toughness of W-alloys is by ductile-phase toughening (DPT). In this method, a ductile phase is included in a brittle matrix to prevent on inhibit crack propagation by crack blunting, crack bridging, crack deflection, and crack branching. Model examples of DPT tungsten are explored in this study, including W-Cu and W-Ni-Fe powder product composites. Three-point and four-point notched and/or pre-cracked bend samples were tested at several strain rates and temperatures to help understand deformation, cracking, and toughening in these materials. Data from these tests are used for developing and calibrating crack-bridging models. Finite element damage mechanics models are introduced as a modeling method that appears to capture the complexity of crack growth in these materials.

  13. An investigation of the loss of ductility in hydrogen charged beta-Ti alloys

    Science.gov (United States)

    Robertson, Ian M.

    1995-01-01

    The high strength, low density, and good corrosion resistance of Ti-based alloys make them candidate materials for a number of applications in the aerospace industry. A major limitation in the use of these alloys in the advanced hypersonic flight vehicle program is their susceptibility to hydrogen embrittlement. This study focuses on the hydrogen sensitivity of TIMETAL 21S beta-Ti alloy. The material received was in the form of grip-ends of failed tensile test samples which had been exposed to different charging conditions (combinations of hydrogen pressure and temperature). The samples received, the charging conditions, and their fracture mode are discussed. It can be seen that the fracture behavior changes from ductile to brittle with increasing hydrogen content, but the transition in behavior occurs for a small increase in hydrogen concentration. The aim of this program was to assess the microstructural differences between the ductile and brittle alloys to ascertain the embrittlement mechanism. A range of tools which included x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used.

  14. Strength-ductility relationships in intermediate purity hot-pressed beryllium

    International Nuclear Information System (INIS)

    Stonehouse, A.J.; Bielawski, C.A.; Paine, R.M.

    1977-01-01

    The strength of vacuum hot-pressed, intermediate purity beryllium may be substantially increased without sacrifice of the strain capacity of the present grade (S-65) through decrease in the average grain size. Tensile strength of 517 MPa, 0.2% offset yield strength of 414 MPa with minimum 3% tensile elongation in all test directions could be commercially achieved. The tangent modulus of such material is quite attractive and suffers only about 10% degradation from room temperature to 260 0 C. The tangent modulus is dramatically enhanced by the presence of a yield point. The ductility of the materials studied did not appear to be affected by the BeO content across the range of 0.5 to 2.0% using nominal -44 to -15 μm powder particle sizes. All fine-grained pressings exhibited yield points in the as-pressed condition. Either full-density or sub-density hot-pressed billets given a hot isostatic pressing treatment without the use of cans showed only slight yield points after the HIP treatment with essentially the same strength and ductility factors as in the pressed condition. A plot of grain size vs yield strength in the as-pressed condition projects to an intercept with the fracture strength line at about 3 μm grain size. A similar plot after the HIP treatment shows a yield strength line parallel to the fracture strength line with no projected intercept predicting a completely brittle material. (author)

  15. Thermomechanical treatment of austempered ductile iron

    Directory of Open Access Journals (Sweden)

    A. A. Nofal

    2007-11-01

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

  16. Nuclear radius deduced from proton diffraction by a black nucleus

    Science.gov (United States)

    Kohama, Akihisa; Iida, Kei; Oyamatsu, Kazuhiro

    2004-06-01

    We find a new method to deduce nuclear radii from proton-nucleus elastic scattering data. In this method, a nucleus is viewed as a “black” sphere. A diffraction pattern of protons by this sphere is equivalent to that of the Fraunhofer diffraction by a circular hole of the same radius embedded in a screen. We determine the black sphere radius in such a way as to reproduce the empirical value of the angle of the observed first diffraction peak. It is useful to identify this radius multiplied by √(3/5 ) with the root-mean-square matter radius of the target nucleus. For most stable isotopes of masses heavier than 50, it agrees, within the error bars, with the values that were deduced in previous elaborate analyses from the data obtained at proton incident energies higher than ˜800 MeV .

  17. Deducing Energy Consumer Behavior from Smart Meter Data

    DEFF Research Database (Denmark)

    Ebeid, Emad Samuel Malki; Heick, Rune; Jacobsen, Rune Hylsberg

    2017-01-01

    The ongoing upgrade of electricity meters to smart ones has opened a new market of intelligent services to analyze the recorded meter data. This paper introduces an open architecture and a unified framework for deducing user behavior from its smart main electricity meter data and presenting...... the recognized home appliances. The framework uses open standard interfaces for exchanging data. The framework has been validated through comprehensive experiments that are related to an European Smart Grid project....

  18. Mechanical Behaviour of Materials Volume II Fracture Mechanics and Damage

    CERN Document Server

    François, Dominique; Zaoui, André

    2013-01-01

    Designing new structural materials, extending lifetimes and guarding against fracture in service are among the preoccupations of engineers, and to deal with these they need to have command of the mechanics of material behaviour. This ought to reflect in the training of students. In this respect, the first volume of this work deals with elastic, elastoplastic, elastoviscoplastic and viscoelastic behaviours; this second volume continues with fracture mechanics and damage, and with contact mechanics, friction and wear. As in Volume I, the treatment links the active mechanisms on the microscopic scale and the laws of macroscopic behaviour. Chapter I is an introduction to the various damage phenomena. Chapter II gives the essential of fracture mechanics. Chapter III is devoted to brittle fracture, chapter IV to ductile fracture and chapter V to the brittle-ductile transition. Chapter VI is a survey of fatigue damage. Chapter VII is devoted to hydogen embrittlement and to environment assisted cracking, chapter VIII...

  19. Effect of water on ductility and fatigue strength of austempered ductile cast iron (ADI)

    OpenAIRE

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

    2006-01-01

    In order to study the mechanism of decreasing the tensile strength and elongation of Austempered Ductile Cast Iron (ADI) in the wet condition, various tension tests and impact test were carried out. And the three point bending fatigue tests were carried out on ADI and annealed 0.55% carbon steel to clarify the influence of water on fatigue strength. The main conclusions areas follows. Embrittlement by water begins when the plastic deformation start in tension test. The fatigue limit of ADI in...

  20. On the applicability of local approaches for the determination of the failure behavior of ductile steels

    International Nuclear Information System (INIS)

    Kussmaul, K.; Eisele, U.; Seidenfuss, M.

    1992-01-01

    The strength and deformation behavior of specimens and components is, on one hand, influenced by the local state of stress and strain and, on the other hand by the chemical composition and the microstructure of the material used. Using two different steels it was investigated in how far it is possible to predict the failure behavior of specimens and components qualitatively and quantitatively by means of local approaches. For this purpose two methods differing considerably from the basic idea were chosen. For the description of the failure behavior so-called damage models were used. These damage models try to describe numerically the process developing microscopically and finally leading to fracture by means of continuum mechanical approaches in order to calculate the macroscopical failure behavior. The results show that for ductile materials the damage models allow a very accurate calculation of smooth and notched specimens and components. The efforts presently required for the calculation are however still very high. Analyses using fracture mechanics approaches (J-Integral) in combination with the local stress states (multiaxiality) were performed to describe the failure behavior. With this approach it was tried to calculate crack initiation and maximum load of precracked specimens and components. The fracture mechanics methods are to be preferred for cracked components if an engineering estimation of crack initiation and maximum load is required only, since the calculational efforts of the fracture mechanics methods are much lower than those of the damage models

  1. Ductile crack growth resistance of PWR components. Application for structural integrity assessment

    International Nuclear Information System (INIS)

    Bethmont, M.; Eripret, C.; Le Delliou, P.; Frund, J.M.

    1995-01-01

    Structural integrity assessment of PWR components, as pressure vessel and piping, needs to evaluate the ductile crack growth resistance which is generally characterized by J resistance curves (or J-R curves) based on the path-independent J Integral. These curves are more often obtained from laboratory tests with small specimens as CT-specimens and their application to large component safety analysis could be questionable Indeed, it is well known that J-R curves could depend on the specimen size and on the loading mode (i.e. bending stress versus tensile stress) but this dependency could be different from one material to another. This means that it would depend not only on the stress-strain state but also on the actual local fracture mechanisms (i. e. the damage) occurring before the crack initiation or during the crack propagation. The purpose of this paper is to gather some results of crack growth resistance measurement studied at EDF with different materials in order to show how the effect of the parameters, as specimen geometry and mode of loading, is directly related to the local fracture mechanisms or the microstructure of the materials. For that a number of results are analysed by means of the local approach of fracture which is a very useful tool to predict quantitatively the J-R curve dependency, related to fracture mechanisms (authors). 12 refs., 9 figs

  2. Hydro-fracture in the laboratory: matching diagnostic seismic signals to fracture networks

    Science.gov (United States)

    Gehne, S.; Benson, P. M.; Koor, N.; Dobson, K. J.; Enfield, M.; Barber, A.

    2017-12-01

    Hydraulic fracturing is a key process in both natural (e.g. dyke intrusion) and engineered environments (e.g. shale gas). To better understand this process, we present new data from simulated hydraulic fracturing in a controlled laboratory environment in order to track fracture nucleation (location) and propagation (velocity) in space and time to assess the fracture mechanics and developing fracture network. Fluid overpressure is used to generate a permeable network of micro tensile fractures in an anisotropic sandstone and a highly anisotropic shale. A newly developed technique, using a steel guide arrangement to direct pressurised fluid into a sealed section of an axially drilled conduit, allows the pore fluid to contact the rock directly and to initiate tensile fractures from a pre-defined zone inside the sample. Acoustic emission location is used to record and map the nucleation and development of the micro-fracture network. For both rock types, fractures progresses parallel to the bedding plane (short-transverse) if the bedding plane is aligned with the direction of σ1 requiring breakdown pressures of approximately 7 and 13MPa respectively at a confining pressure of 8MPa. The data also indicates a more ductile behaviour of the shale than expected. We use X-Ray Computed Tomography (CT) to evaluate the evolved fracture network in terms of fracture pattern and aperture. Hydraulic fracturing produces very planar fractures in the shale, with axial fractures over the entire length of the sample broadly following the bedding. In contrast, fractures in the sandstone are more diffuse, linking pore spaces as they propagate. However, secondary micro cracking, branching of the main fracture, are also observed. These new experiments suggest that fracture pattern, fracture propagation trajectories, and fracturing fluid pressures are predominantly controlled by the interaction between the anisotropic mechanical properties of the rock and the anisotropic stress environment.

  3. Carbon content of austenite in austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-06-05

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

  4. High-temperature ductility of electro-deposited nickel

    Science.gov (United States)

    Dini, J. W.; Johnson, H. R.

    1977-01-01

    Work done during the past several months on high temperature ductility of electrodeposited nickel is summarized. Data are presented which show that earlier measurements made at NASA-Langley erred on the low side, that strain rate has a marked influence on high temperature ductility, and that codeposition of a small amount of manganese helps to improve high temperature ductility. Influences of a number of other factors on nickel properties were also investigated. They included plating solution temperature, current density, agitation, and elimination of the wetting agent from the plating solution. Repair of a large nozzle section by nickel plating is described.

  5. Combined macrosopic and microscopic approach to the fracture of metals, period July 1974--June 1975. Technical progress report No. 38

    International Nuclear Information System (INIS)

    Gurland, J.; Rice, J.R.

    1975-07-01

    During the report period major studies have been completed on (1) the microscale fracture conditions for the brittle and ductile fracture initiation modes at a macroscopic crack tip, (2) the formulation of dilational plasticity constitutive relations for void containing materials as applied to the inception of ductile rupture, (3) cavity growth during diffusive rupture processes as encountered in creep rupture at low stress but high temperature, and (4) particle and boundary strengthening mechanisms in carbon steels. In addition, work has continued on crack tip modeling by finite elements and mechanisms of ductile void growth near a crack tip

  6. Calorimetric examinations of austempered ductile iron ADI

    Directory of Open Access Journals (Sweden)

    F. Binczyk

    2007-12-01

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

  7. Anisotropy and fracture modes I and III in a flange test specimen

    DEFF Research Database (Denmark)

    Nielsen, Chris Valentin; Silva, Carlos M.A.; Alves, Luis M.

    2015-01-01

    Formability in bulk metal forming was revisited in a recent paper by considering plasticity, ductile damage and fracture modes for a number of test specimens. One of the test specimens is a flange component showing failure by both fracture mode I and mode III upon compression between two flat...

  8. Microalloying Boron Carbide with Silicon to Achieve Dramatically Improved Ductility.

    Science.gov (United States)

    An, Qi; Goddard, William A

    2014-12-04

    Boron carbide (B4C) is a hard material whose value for extended engineering applications such as body armor; is limited by its brittleness under impact. To improve the ductility while retaining hardness, we used density functional theory to examine modifying B4C ductility through microalloying. We found that replacing the CBC chain in B4C with Si-Si, denoted as (B11Cp)-Si2, dramatically improves the ductility, allowing a continuous shear to a large strain of 0.802 (about twice of B4C failure strain) without brittle failure. Moreover, (B11C)-Si2 retains low density and high hardness. This ductility improvement arises because the Si-Si linkages enable the icosahedra accommodate additional shear by rotating instead of breaking bonds.

  9. Solidification, processing and properties of ductile cast iron

    DEFF Research Database (Denmark)

    Tiedje, Niels Skat

    2010-01-01

    Ductile cast iron has been an important engineering material in the past 50 years. In that time, it has evolved from a complicated material that required the foundry metallurgist's highest skill and strict process control to being a commonly used material that can easily be produced with modern...... of the latest years of research indicate that ductile cast iron in the future will become a highly engineered material in which strict control of a range of alloy elements combined with intelligent design and highly advanced processing allows us to target properties to specific applications to a much higher...... and to illustrate how ductile iron's properties are optimised, the essentials of heat treatment are described too. It is the hope that researchers will find a comprehensive treatment of ductile cast iron metallurgy and that engineers and designers will be presented with the latest information on, and references to...

  10. Robustness Evaluation of Timber Structures with Ductile Behaviour

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard; Cizmar, D.

    2009-01-01

    as a parallel system. A measure of ductile behaviour is introduced. For different values of this measure the system reliability is estimated based on Monte Carlo simulation where correlation between the strength of structural elements and load models for permanent and live load are introduced. The results......The present paper considers robustness evaluation of timber structures where the ductile behavior of joints of timber material is taken into account. The robustness analysis is based on the structural reliability framework used on a simplified mechanical system modelling a structural timber system...... indicate the reliability of a structural timber ystem can be increased apprximately 20 % awarding the ductile behaviour. At last the paper discusses possible structural timber systems which have potential for providing ductility and redundancy....

  11. Extended Finite Element Method XFEM for ductile tearing: Large crack growth modelization based on the transition from a continuous medium to the crack via a cohesive zone model

    International Nuclear Information System (INIS)

    Simatos, A.

    2010-01-01

    This work extends the applicability of local models for ductile fracture to large crack growth modelization for ductile tearing. This is done inserting a cohesive zone model whose constitutive law is identified in order to be consistent with the local model. The consistency is obtained through the cohesive law incremental construction which ensures the equivalence of the energy and of the mechanical response of the models. The extension of the applicability domain of the local modelization is enabled via the XFEM framework which allows for maintaining the mechanical energy during the crack extension step. This method permits also to introduce the cohesive zone model during the calculation without regards to the mesh of the structure for its maximal tensile stress. To apply the XFEM to ductile tearing, this method is extended to non linear problems (Updated Lagrangian Formulation, large scale yield plasticity). The cohesive zone model grows when the criterion defined in term of porosity, tested at the front of the cohesive crack front, is verified. The cohesive zone growth criterion is determined in order to model most of the damaging phase with the local model to ensure that the modelization takes into account the triaxiality ratio history accurately. The proposed method is applied to the Rousselier local model for ductile fracture in the XFEM framework of Cast3M, the FE software of the CEA. (author) [fr

  12. 49 CFR 192.373 - Service lines: Cast iron and ductile iron.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Service lines: Cast iron and ductile iron. 192.373... Regulators, and Service Lines § 192.373 Service lines: Cast iron and ductile iron. (a) Cast or ductile iron... cast iron pipe or ductile iron pipe is installed for use as a service line, the part of the service...

  13. Numerical modelling of Charpy-V notch test by local approach to fracture. Application to an A508 steel in the ductile-brittle transition range; Modelisation de l'essai Charpy par l'approche locale de la rupture. Application au cas de l'acier 16MND5 dans le domaine de transition

    Energy Technology Data Exchange (ETDEWEB)

    Tanguy, B

    2001-07-15

    Ferritic steels present a transition of the rupture mode which goes progressively of a brittle rupture (cleavage) to a ductile rupture when the temperature increases. The following of the difference of the transition temperature of the PWR vessel steel by the establishment of toughness curves makes of the Charpy test an integrating part of the monitoring of the French PWR reactors. In spite of the advantages which are adapted to it in particular its cost, the Charpy test does not allow to obtain directly a variable which characterizes a crack propagation resistance as for instance the toughness used for qualifying the mechanical integrity of a structure. This work deals with the establishment of the through impact strength-toughness in the transition range of the vessel steel: 16MND5 from a non-empirical approach based on the local approach of the rupture. The brittle rupture is described by the Beremin model (1983), which allows to describe the dispersion inherent in this rupture mode. The description of the brittle fissure is carried out by the GTN model (1984) and by the Rousselier model (1986). This last model has been modified in order to obtain a realistic description of the brittle damage in the case of fast solicitations and of local heating. The method proposed to determine the parameters of the damage models depends only of tests on notched specimens and of the inclusion data of the material. The behaviour is described by an original formulation parametrized in temperature which allows to describe all the tests carried out in this study. Before using this methodology, an experimental study of the behaviour and of the rupture modes of the steel 16MND5 has been carried out. From the toughness tests carried out in quasi-static and dynamical conditions, it has been revealed that this steel does not present important unwedging of its toughness curve due to the velocity effect. In the transition range, local heating of about 150 C have been measured in the root

  14. Influence of phosphorus on the creep ductility of copper

    International Nuclear Information System (INIS)

    Sandström, Rolf; Wu, Rui

    2013-01-01

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

  15. Reduction of cross section area at fracture in tensile test: measurement and applications for flat sheet steels

    Science.gov (United States)

    Larour, P.; Freudenthaler, J.; Weissböck, T.

    2017-09-01

    This contribution deals with the use of maximum thinning and reduction of sample cross section area at fracture after tensile testing and applications for industrial flat sheet steels. Although included in all usual tensile testing standards, this mechanical property (“Z-value”) has long been neglected for flat sheet materials. It happens however to include some most valuable information on local ductility at fracture of sheet steels. This is increasingly needed for a more suitable description and ranking of newly developed advanced high strength sheet steels with regard to local ductility (stretch-flangeability, bendability, crash-ability) versus global ductility (deep-drawability). It is shown in this investigation that the ISO16630 punched and milled hole expansion ratio correlates linearly with the relative thickness reduction at fracture. A classification of cold rolled AHSS-UHSS sheet steels is attempted by plotting the relative thickness & area reduction at fracture vs. uniform and fracture elongation.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-03-01

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

  17. Martensite transformations influence in austenite stainless steel fractures

    International Nuclear Information System (INIS)

    Fonseca, H.; Monteiro, S.N.

    1976-07-01

    The influence of martensitic transformation on the fracture of tensile specimens of type AISI 310, and type 302, stainless steels was studied in the temperature interval from 25 0 C to -196 0 C. The influence of the metastability through the amount and rate of martensite transformation leading to high stresses and work hardening, apparently explains the brittle characteristics observed in the fracture of type 302 alloy as well as its ductile nature at -196 0 C [pt

  18. Fracture of Shape Memory Alloys

    OpenAIRE

    Miyazaki, Shuichi; Otsuka, Kazuhiro

    1981-01-01

    The initiation and the propagation of cracks during both quenching and deformation in polycrystalline Cu-Al-Ni alloys have been investigated under various conditions. The fracture surfaces of Ti-Ni and Cu-Al-Ni alloys were also observed by a scanning electron microscope. From these results, it was concluded that the brittleness of Cu-Al-Ni alloy and other β phase alloys are due to large elastic anisotropy and large grain sizes, while that the large ductility in Ti-Ni alloy being due to the sm...

  19. Study on the structural integrity of a PWR vessel according to the ductile cracking instability theory; Avaliacao da integridade estrutural de um vaso PWR segundo a teoria da instabilidade do rasgamento ductil

    Energy Technology Data Exchange (ETDEWEB)

    Tarpani, Jose Ricardo; Spinelli, Dirceu [Sao Paulo Univ., Sao Carlos, SP (Brazil). Escola de Engenharia. Dept. de Engenharia de Materiais

    1996-12-31

    Analytical predictions of PWR vessel instability have been made according to Linear Elastic criterion K{sub lC} and Elastic-Plastic Fracture Mechanics Ji, J{sub 50} and J {sub inst}. Special attention was given to the influence of crack depth and length on both approaches, as well as to the data extrapolation procedures on elasto-plasticity. Simple and didactic format has been supplied for the results evaluation in terms of internal pressure, wall-through strain gradient and ductile stable crack extension. (author) 4 refs., 4 figs., 1 tab.

  20. Deducing Energy Consumer Behavior from Smart Meter Data

    Directory of Open Access Journals (Sweden)

    Emad Ebeid

    2017-07-01

    Full Text Available The ongoing upgrade of electricity meters to smart ones has opened a new market of intelligent services to analyze the recorded meter data. This paper introduces an open architecture and a unified framework for deducing user behavior from its smart main electricity meter data and presenting the results in a natural language. The framework allows a fast exploration and integration of a variety of machine learning algorithms combined with data recovery mechanisms for improving the recognition’s accuracy. Consequently, the framework generates natural language reports of the user’s behavior from the recognized home appliances. The framework uses open standard interfaces for exchanging data. The framework has been validated through comprehensive experiments that are related to an European Smart Grid project.

  1. Effect of Stress State on Fracture Features

    Science.gov (United States)

    Das, Arpan

    2018-02-01

    Present article comprehensively explores the influence of specimen thickness on the quantitative estimates of different ductile fractographic features in two dimensions, correlating tensile properties of a reactor pressure vessel steel tested under ambient temperature where the initial crystallographic texture, inclusion content, and their distribution are kept unaltered. It has been investigated that the changes in tensile fracture morphology of these steels are directly attributable to the resulting stress-state history under tension for given specimen dimensions.

  2. Prediction of fracture toughness temperature dependence applying neural network

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Hadraba, Hynek; Chlup, Zdeněk; Šmída, T.

    2011-01-01

    Roč. 11, č. 1 (2011), s. 9-14 ISSN 1451-3749 R&D Projects: GA ČR(CZ) GAP108/10/0466 Institutional research plan: CEZ:AV0Z20410507 Keywords : brittle to ductile transition * fracture toughness * artificial neural network * steels Subject RIV: JL - Materials Fatigue, Friction Mechanics

  3. Comprehensive Understanding of Ductility Loss Mechanisms in Various Steels with External and Internal Hydrogen

    Science.gov (United States)

    Takakuwa, Osamu; Yamabe, Junichiro; Matsunaga, Hisao; Furuya, Yoshiyuki; Matsuoka, Saburo

    2017-11-01

    Hydrogen-induced ductility loss and related fracture morphologies are comprehensively discussed in consideration of the hydrogen distribution in a specimen with external and internal hydrogen by using 300-series austenitic stainless steels (Types 304, 316, 316L), high-strength austenitic stainless steels (HP160, XM-19), precipitation-hardened iron-based super alloy (A286), low-alloy Cr-Mo steel (JIS-SCM435), and low-carbon steel (JIS-SM490B). External hydrogen is realized by a non-charged specimen tested in high-pressure gaseous hydrogen, and internal hydrogen is realized by a hydrogen-charged specimen tested in air or inert gas. Fracture morphologies obtained by slow-strain-rate tensile tests (SSRT) of the materials with external or internal hydrogen could be comprehensively categorized into five types: hydrogen-induced successive crack growth, ordinary void formation, small-sized void formation related to the void sheet, large-sized void formation, and facet formation. The mechanisms of hydrogen embrittlement are broadly classified into hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP). In the HEDE model, hydrogen weakens interatomic bonds, whereas in the HELP model, hydrogen enhances localized slip deformations. Although various fracture morphologies are produced by external or internal hydrogen, these morphologies can be explained by the HELP model rather than by the HEDE model.

  4. Relations between a micro-mechanical model and a damage model for ductile failure in shear

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Nielsen, Kim Lau

    2010-01-01

    Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro......-cracks, which rotate and elongate until interaction with neighbouring micro-cracks gives coalescence. Thus, the failure mechanism is very different from that under tensile loading. Also, the Gurson model has recently been extended to describe failure in shear, by adding a damage term to the expression...... for the growth of the void volume fraction, and it has been shown that this extended model can represent experimental observations. Here, numerical studies are carried out to compare predictions of the shear-extended Gurson model with the shear failures predicted by the micro-mechanical cell model. Both models...

  5. Constitutive modeling of void-growth-based tensile ductile failures with stress triaxiality effects

    KAUST Repository

    Mora Cordova, Angel

    2014-07-01

    In most metals and alloys, the evolution of voids has been generally recognized as the basic failure mechanism. Furthermore, stress triaxiality has been found to influence void growth dramatically. Besides strain intensity, it is understood to be the most important factor that controls the initiation of ductile fracture. We include sensitivity of stress triaxiality in a variational porous plasticity model, which was originally derived from hydrostatic expansion. Under loading conditions rather than hydrostatic deformation, we allow the critical pressure for voids to be exceeded so that the growth due to plasticity becomes dependent on the stress triaxiality. The limitations of the spherical void growth assumption are investigated. Our improved constitutive model is validated through good agreements with experimental data. Its capacity for reproducing realistic failure patterns is also indicated by a numerical simulation of a compact tensile (CT) test. © 2013 Elsevier Inc.

  6. Heavy-section steel technology program: Fracture issues

    International Nuclear Information System (INIS)

    Pennell, W.E.

    1992-01-01

    Large-scale fracture mechanics tests have resulted in the identification of a number of fracture technology issues. Identification of additional issues has come from the reactor vessel materials irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized thermal shock (PTS) analysis. Mixed mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low-strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws in the welds of ring-forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy Section Steel Technology (HSST) program at ORNL

  7. Contribution to the research on fracture properties of metals in the elasto-plastic field

    International Nuclear Information System (INIS)

    Rousselier, G.; Electricite de France, 77 - Ecuelles. Dept. Etudes des Materiaux)

    1979-01-01

    Standard Fracture Mechanics theories proved unsuccessful for the treatment of ductile fracture in metals. We have shown the necessity of better knowledge and satisfactory modelling of the fracture process, prior to any application to cracked bodies. In that way we developed stress-strain laws which take into consideration the growth of voids during ductile fracture. The damage resulting from void growth is characterized by internal parameters. Finite strain analysis leads to material instability, corresponding to the stage of void coalescence and material decohesion. This latter result is only true in a finite strain analysis. In the infinitesimal strain finite element numerical analysis of three-point bend specimens, a local fracture criterion is used. The experimental determination of this criterion is performed with axisymmetrical notched tension specimens, which allow the investigation of various stress triaxialities at fracture. The numerical analysis proved effective in the modelling of stable crack growth and size effect, and was compared with experimental results [fr

  8. Novel alpha-zirconium phosphonates for the reinforcement of ductile thermoplastics

    Science.gov (United States)

    Furman, Benjamin R.

    2007-12-01

    Ductile thermoplastics are useful additives for providing fracture toughness to brittle thermosetting polymers; however, this toughening is usually accompanied by a significant decrease in elastic modulus. Therefore, alpha-zirconium phosphonates (ZrP) were developed and investigated as reinforcing nano-scale fillers that increase the yield strength and elastic modulus of a polyester thermoplastic without causing a reduction in its ductility. ZrP materials are synthetic layered compounds that are imbued with targeted organic surface functionalities and whose structural development can be carefully controlled in the laboratory. Ether-terminal alkyl ZrP materials were designed and synthesized, using a conventional ZrF62--mediated preparation, with the intent of developing strong dipole-dipole interactions between the layer surfaces and polyester macromolecules. Additionally, a general method for using lamellar lyotropic liquid crystals (LLC's) as supramolecular templates for alkyl ZrP was evaluated, whose products showed promising similarity to the conventionally prepared materials. The LLC-forming characteristics of several organophosphonate preparations were determined, showing improved mesophase stability with mixed amphiphiles and preparation with R4N + counterions. A mixed-surface octyl/methoxyundecyl ZrP was produced and combined with polycaprolactone (PCL) and polymethylmethacrylate (PMMA) in concentrations up to 50% (w/w). The mechanical properties of the ZrP/PCL nanocomposite were evaluated by tensile, flexural, and dynamic mechanical testing methods. Nanocomposites containing 5% (w/w) ZrP showed significant increases in tensile yield stress and elastic modulus without suffering any loss of ductility versus the unfilled polymer. Layer delamination from the ZrP tactoids was minimal and did not occur through an intercalative mechanism. Higher ZrP loadings resulted in the agglomeration of tactoids, leading to defect structures and loss of strength and ductility

  9. Hip Fracture

    Science.gov (United States)

    ... hip fractures in people of all ages. In older adults, a hip fracture is most often a result of a fall from a standing height. In people with very weak bones, a hip fracture can occur simply by standing on the leg and twisting. Risk factors The rate of hip fractures increases substantially with ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-07-01

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

  11. Identification of modes of fracture in a 2618-T6 aluminum alloy using stereophotogrammetry

    Energy Technology Data Exchange (ETDEWEB)

    Salas Zamarripa, A., E-mail: a.salaszamarripa@gmail.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon. Av. Universidad S/N, Ciudad Universitaria, C.P. 66451, Apartado Postal 076 Suc. ' F' San Nicolas de los Garza, N.L. (Mexico); Pinna, C.; Brown, M.W. [Department of Mechanical Engineering, University of Sheffield. Sir Frederick Mappin Building, Mappin Street, Sheffield, S1 3JD (United Kingdom); Mata, M.P. Guerrero; Morales, M. Castillo; Beber-Solano, T.P. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon. Av. Universidad S/N, Ciudad Universitaria, C.P. 66451, Apartado Postal 076 Suc. ' F' San Nicolas de los Garza, N.L. (Mexico)

    2011-12-15

    The identification and the development of a quantification technique of the modes of fracture in fatigue fracture surfaces of a 2618-T6 aluminum alloy were developed during this research. Fatigue tests at room and high temperature (230 Degree-Sign C) were carried out to be able to compare the microscopic fractographic features developed by this material under these testing conditions. The overall observations by scanning electron microscopy (SEM) of the fracture surfaces showed a mixture of transgranular and ductile intergranular fracture. The ductile intergranular fracture contribution appears to be more significant at room temperature than at 230 Degree-Sign C. A quantitative methodology was developed to identify and to measure the contribution of these microscopic fractographic features. The technique consisted of a combination of stereophotogrammetry and image analysis. Stereo-pairs were randomly taken along the crack paths and were then analyzed using the profile module of MeX software. The analysis involved the 3-D surface reconstruction, the trace of primary profile lines in both vertical and horizontal directions within the stereo-pair area, the measurements of the contribution of the modes of fracture in each profile, and finally, the calculation of the average contribution in each stereo-pair. The technique results confirmed a higher contribution of ductile intergranular fracture at room temperature than at 230 Degree-Sign C. Moreover, there was no indication of a direct relationship between this contribution and the strain amplitudes range applied during the fatigue testing. - Highlights: Black-Right-Pointing-Pointer Stereophotogrammetry and image analysis as a measuring tool of modes of fracture in fatigue fracture surfaces. Black-Right-Pointing-Pointer A mixture of ductile intergranular and transgranular fracture was identified at room temperature and 230 Degree-Sign C testing. Black-Right-Pointing-Pointer Development of a quantitative methodology to

  12. Ductility of reinforced concrete columns confined with stapled strips

    International Nuclear Information System (INIS)

    Tahir, M.F.; Khan, Q.U.Z.; Shabbir, F.; Sharif, M.B.; Ijaz, N.

    2015-01-01

    Response of three 150x150x450mm short reinforced concrete (RC) columns confined with different types of confining steel was investigated. Standard stirrups, strips and stapled strips, each having same cross-sectional area, were employed as confining steel around four comer column bars. Experimental work was aimed at probing into the affect of stapled strip confinement on post elastic behavior and ductility level under cyclic axial load. Ductility ratios, strength enhancement factor and core concrete strengths were compared to study the affect of confinement. Results indicate that strength enhancement in RC columns due to strip and stapled strip confinement was not remarkable as compared to stirrup confined column. It was found that as compared to stirrup confined column, stapled strip confinement enhanced the ductility of RC column by 183% and observed axial capacity of stapled strip confined columns was 41 % higher than the strip confined columns. (author)

  13. Wear Resistance of Austempered Ductile Iron with Nanosized Additives

    Science.gov (United States)

    Kaleicheva, J. K.; Mishev, V.

    2018-01-01

    The wear resistance, microstructure and mechanical properties of austempered ductile iron (ADI) with nanosized additives of cubic boron nitride cBN are investigated. Samples of ductile iron are put under austhempering at the following conditions: heating at 900°С, 1 h and isothermal retention at 280оС, 2 h and 380°С, 2 h with the aim to achieve a lower bainitic structure and an upper bainitic structure. The experimental wear testing of austempered ductile irons is performed in friction conditions of a fixed abrasive by a cinematic scheme „pin - disc” using an accelerated testing method and device. The microstructure of the ADI is investigated by metallographic and X-Ray analyses. The Vickers hardness testing and impact strength examination are carried out. The influence of the nanosized additives of cBN on the wear resistance, microstructure, impact strength and hardness of the ADI is investigated.

  14. Engineered Cooling Process for High Strength Ductile Iron Castings

    Science.gov (United States)

    Lekakh, Simon N.; Mikhailov, Anthony; Kramer, Joseph

    Professor Stefanescu contributed fundamentally to the science of solidification and microstructural evolutions in ductile irons. In this article, the possibility of development of high strength ductile iron by applying an engineered cooling process after casting early shake out from the sand mold was explored. The structures in industrial ductile iron were experimentally simulated using a computer controlled heating/cooling device. CFD modeling was used for process simulation and an experimental bench scale system was developed. The process concept was experimentally verified by producing cast plates with 25 mm wall thickness. The tensile strength was increased from 550 MPa to 1000 MPa in as-cast condition without the need for alloying and heat treatment. The possible practical applications were discussed.

  15. Brittle and ductile friction and the physics of tectonic tremor

    Science.gov (United States)

    Daub, Eric G.; Shelly, David R.; Guyer, Robert A.; Johnson, P.A.

    2011-01-01

    Observations of nonvolcanic tremor provide a unique window into the mechanisms of deformation and failure in the lower crust. At increasing depths, rock deformation gradually transitions from brittle, where earthquakes occur, to ductile, with tremor occurring in the transitional region. The physics of deformation in the transition region remain poorly constrained, limiting our basic understanding of tremor and its relation to earthquakes. We combine field and laboratory observations with a physical friction model comprised of brittle and ductile components, and use the model to provide constraints on the friction and stress state in the lower crust. A phase diagram is constructed that characterizes under what conditions all faulting behaviors occur, including earthquakes, tremor, silent transient slip, and steady sliding. Our results show that tremor occurs over a range of ductile and brittle frictional strengths, and advances our understanding of the physical conditions at which tremor and earthquakes take place.

  16. 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.

  17. Effect of Ti and B microadditions on the hot ductility behavior of a High-Mn austenitic Fe–23Mn–1.5Al–1.3Si–0.5C TWIP steel

    Energy Technology Data Exchange (ETDEWEB)

    Mejía, I., E-mail: imejia@umich.mx [Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U-5”, Ciudad Universitaria, 58066 Morelia, Michoacán, México (Mexico); Salas-Reyes, A.E. [Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U-5”, Ciudad Universitaria, 58066 Morelia, Michoacán, México (Mexico); Calvo, J.; Cabrera, J.M. [Departament de Ciència dels Materials i Enginyeria Metallurgica, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundació CTM Centre Tecnològic, Plaça de la Ciència, 2-08243 Manresa (Spain)

    2015-11-11

    This research work studies the effect of combined Ti and B microadditions and the solidification route on the hot ductility behavior of a high-Mn austenitic Twinning Induced Plasticity (TWIP) steel. For this purpose, uniaxial hot tensile tests were carried out at different temperatures between 700 and 1100 °C under a constant strain rate of 10{sup −3} s{sup −1}. The hot ductility was determined by measuring the reduction of transverse area (%RA) after specimen rupture. Characterization was performed by SEM-EBSD and TEM techniques in order to identify the relationship between microstructural features and cracking phenomena. Results indicate that the early occurrence of dynamic recrystallization (DRX) at the intermediate temperature range (800–900 °C) is the favorable mechanism that enhances the ductility, achieving RA values up to 82%. These high RA values are discussed in terms of the boron effect on the improvement of the grain-boundaries cohesion through non-equilibrium segregation, and Ti(C,N) precipitation, which reduces the formation of harmful precipitates such as BN and AlN. Additionally, the Fe{sub 23}(B,C){sub 6} and B{sub 4}C compounds were identified, which are less detrimental to hot ductility than boron-nitride compounds. Finally, the fracture surfaces of the present TWIP steels in the temperature range of the highest ductility indicate that the failure mode is of the ductile type as evidenced by the presence of many dimples.

  18. Properties and Structure of High-Silicone Austempered Ductile Iron

    Directory of Open Access Journals (Sweden)

    Krzyńska A.

    2014-06-01

    Full Text Available The results presented in this paper are a continuation of the previously published studies. The results of hest treatment of ductile iron with content 3,66%Si and 3,80% Si were produced. The experimental castings were subjected to austempering process for time 30, 60 and 90 minutes at temperature 300°C. The mechanical properties of heat treated specimens were studied using tensile testing and hardness measurement, while microstructures were evaluated with conventional metallographic observations. It was again stated that austempering of high silicone ferritic matrix ductile iron allowed producing ADI-type cast iron with mechanical properties comparable with standard ADI.

  19. Toughened microstructures for ductile phase reinforced molybdenum disilicide

    International Nuclear Information System (INIS)

    Pickard, S.M.; Ghosh, A.K.

    1995-01-01

    Various morphologies of ductile Nb refractory metal reinforcement are incorporated into a MoSi 2 matrix using powder metallurgy, including single-ply laminates, continuous metal ribbons and sections of 2-dimensional wire mesh. Hot forging techniques are used to redistribute the reinforcement and change the dimensions and the aspect ratio of the reinforcing metal ligaments. Work-of-rupture measurements are conducted on bend test specimens and precracked tensile specimens of the composite so that the toughness contribution from the various ductile metal morphologies can be assessed according to its effectiveness. Accompanying microstructural examination of crack bridging interaction with the reinforcement is conducted

  20. Phosphorus effect on fracture properties of structural steels

    International Nuclear Information System (INIS)

    Goritskij, V.M.; Guseva, I.A.

    1985-01-01

    Phosphorus content is studied for its effect on fracture peculiarities and fracture toughness. It is supposed that the phosphorus effect on ductile fractures is associated with phosphorus segregation on the ferrite-carbide interfaces. An increase of the phosphorus content in heat-treated 10KhSND steel from 0.020 up to 0.043 wt.% results in a decrease of the pore size and asub(p) value. Close linear correlation is established between critical temperature of embrittlement T 50 and √ asub(p) or √ KC values for a number of structural steels with different phosphorus content

  1. fracture criterion

    Indian Academy of Sciences (India)

    Fracture in metallic glasses. What are the connections between nano- and micro- mechanisms and toughness? Metallic glasses are schizophrenic in the fracture sense. PDF Create! 5 Trial www.nuance.com ...

  2. Hand Fractures

    Science.gov (United States)

    ... Thumb Arthritis Thumb Sprains Trigger Finger Tumors Wrist Fracture Hand Safety Fireworks Safety Lawnmower Safety Snowblower safety ... Tunnel Ganglion Cysts Thumb Arthritis Trigger Finger Wrist Fracture Hand Safety Fireworks Safety Lawnmower Safety Snowblower safety ...

  3. Wrist Fractures

    Science.gov (United States)

    ... a Hand Therapist? Media Find a Hand Surgeon Home Anatomy Wrist Fractures Email to a friend * required fields From * To * DESCRIPTION A wrist fracture is a medical term for a broken wrist. The wrist is made up of eight ...

  4. Correlation of physical properties of ceramic materials with resistance to fracture by thermal shock

    Science.gov (United States)

    Lidman, W G; Bobrowsky, A R

    1949-01-01

    An analysis is made to determine which properties of materials affect their resistance to fracture by thermal stresses.From this analysis, a parameter is evaluated that is correlated with the resistance of ceramic materials to fracture by thermal shock as experimentally determined. This parameter may be used to predict qualitatively the resistance of a material to fracture by thermal shock. Resistance to fracture by thermal shock is shown to be dependent upon the following material properties: thermal conductivity, tensile strength, thermal expansion, and ductility modulus. For qualitative prediction of resistance of materials to fracture by thermal shock, the parameter may be expressed as the product of thermal conductivity and tensile strength divided by the product of linear coefficient of thermal expansion and ductility modulus of the specimen.

  5. Transformation plasticity in ductile solids. Annual progress report, June 1, 1993--May 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Olson, G.B.

    1994-04-01

    Research has addressed the role of martensitic transformation plasticity in the enhancement of toughness in high-strength austenitic steels, and the enhancement of formability in multiphase low-alloy sheet steels. In the austenitic steels, optimal processing has achieved a significant increase in strength level, in order to investigate the interaction of strain-induced transformation with the microvoid nucleation and shear localization mechanisms operating at ultrahigh strength levels. The degree of transformation interaction is sensitive to both strength level and degree of constraint. The stress-state dependence of transformation and fracture mechanisms has been investigated in model alloys, comparing behavior in uniaxial tension and blunt-notch tension specimens. A reformulated numerical constitutive model for transformation plasticity has allowed a more thorough analysis of transformation/fracture interactions, including local processes of microvoid nucleation. Processing of a new low alloy steel composition has been optimized to stabilize retained austenite by isothermal bainitic transformation after intercritical annealing. Results show a good correlation of uniform ductility with the austenite amount and stability, and new compositions are designed for improved stability.

  6. Root fractures

    DEFF Research Database (Denmark)

    Andreasen, Jens Ove; Christensen, Søren Steno Ahrensburg; Tsilingaridis, Georgios

    2012-01-01

    The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed.......The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed....

  7. Thermo-Mechanical Processing and Properties of a Ductile Iron

    Energy Technology Data Exchange (ETDEWEB)

    Syn, C.K.; Lesuer, R.R.; Sherby, O.D.

    1997-07-14

    Thermo-mechanical processing of ductile irons is a potential method for enhancing their mechanical properties. A ductile cast iron containing 3.6% C, 2.6% Si and 0.045% Mg was continuously hot-and-warm rolled or one-step press-forged from a temperature in the austenite range (900{degrees}C-1100{degrees}C) to a temperature below the A, temperature. Various amounts of reduction were used (from 60% to more than 90%) followed by a short heat ent at 600`C. The heat ent lead to a structure of fine graphite in a matrix of ferrite and carbides. The hot-and- warm worked materials developed a pearlitic microstructure while the press-forged material developed a spheroidite-like carbide microstructure in the matrix. Cementite-denuded ferrite zones were developed around graphite stringers in the hot-and-warm worked materials, but such zones were absent in the press-forged material. Tensile properties including tensile strength and total elongation were measured along the direction parallel and transverse to the rolling direction and along the direction transverse to the press-forging direction. The tensile ductility and strength both increased with a decrease in the amount of hot-and-warm working. The press- forged materials showed higher strength (645 MPa) than the hot-and-warrn worked materials (575 MPa) when compared at the same ductility level (22% elongation).

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

    Directory of Open Access Journals (Sweden)

    D. Myszka

    2009-01-01

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

  9. Wear and scuffing of austempered ductile iron gears

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

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

  10. APPLICATION OF AUSTEMPERED DUCTILE IRON TO RAIL WHEEL SETS

    Directory of Open Access Journals (Sweden)

    Sacit DÜNDAR

    2003-03-01

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

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

    Directory of Open Access Journals (Sweden)

    Z. Ławrynowicz

    2007-07-01

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

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

    Directory of Open Access Journals (Sweden)

    Krzyńska A.

    2007-01-01

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

  13. Low temperature enhanced ductility of friction stir processed 5083 ...

    Indian Academy of Sciences (India)

    Administrator

    forming loads. The occurrence of a relatively high value of strain rate sensitivity, m of 0⋅45 for a grain size of. 0⋅95 μm, suggests the operation of superplastic deformation under these present experimental conditions. Keywords. AA5083; friction stir processing; ductility; superplasticity. 1. Introduction. Friction stir processing ...

  14. Low temperature enhanced ductility of friction stir processed 5083 ...

    Indian Academy of Sciences (India)

    ... rates, and demonstrated that a decrease in grain size resulted in significantly enhanced ductility and lower forming loads. The occurrence of a relatively high value of strain rate sensitivity, of 0.45 for a grain size of 0.95 m, suggests the operation of superplastic deformation under these present experimental conditions.

  15. Solidification of Hypereutectic Thin Wall Ductile Cast Iron

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels Skat

    2006-01-01

    Hypereutectic ductile iron was cast in green sand moulds with four plates with thickness of 1.5, 2, 3 and 4 mm in each mould. Temperatures were measured in the 3 and 4 mm plate. The temperature curves showed that eutectic solidification was divided into two stages: primary and secondary eutectic...

  16. High-pressure structural stability of the ductile intermetallic ...

    Indian Academy of Sciences (India)

    Administrator

    Murnaghan equation of state fit to the pressure, volume data yielded a bulk modulus of 67∙6 GPa with the pressure derivative of bulk modulus fixed at 4. Keywords. Intermetallics; X-ray ... ners of the unit cell cube occupied by the 'M' element and cube centre occupied by the 'R' element. Although some ductility has been ...

  17. strength and ductility of forged 1200 aluminum alloy reinforced

    African Journals Online (AJOL)

    eobe

    Keywords: Aluminum alloy; annealing; ductility; strength; iron particle. 1. INTRODUCTION. INTRODUCTION. Structural components made from aluminum alloys are vital to the aerospace, automobile and building industries because of their light weight, high strength, good formability and high corrosion resistance. However ...

  18. Construction-friendly ductile shear joints for precast concrete panels

    DEFF Research Database (Denmark)

    Sørensen, Jesper Harrild; Hoang, Linh Cao; Fischer, Gregor

    2015-01-01

    for the mounting of a vertical locking bar. Where limited space is available bending and subsequent straightening of the U-bars are required to assemble the adjacent panels, a procedure which imposes substantial ductility requirements on the reinforcement as well as some manual workload. This paper introduces...

  19. Strength and Ductility of Forged 1200 Aluminum Alloy Reinforced ...

    African Journals Online (AJOL)

    With 50% reduction and fine-sized steel particles (512μm) in aluminum alloy, tensile strength dropped to 160MPa without significant decrease in ductility (1.7). Microstructure of cast samples show the presence of fine Fe particles at grain boundaries after annealing with most of the particles in solid solution. Al3Fe and AlFeSi ...

  20. Effect of specimen size on the fracture toughness of V-4Cr-4Ti

    Energy Technology Data Exchange (ETDEWEB)

    Kurtz, R.J.; Jones, R.H. [Pacific Northwest National Laboratory, Richland, WA (United States); Li, Huaxin

    1996-04-01

    J-R curves were generated using the single specimen unload-compliance technique on four specimens of V-4Cr-4Ti to determine the effect of specimen dimensions on the fracture behavior. Ductile crack initiation and growth was observed in the 6.35 mm thick specimens but not in the 12.70 mm thick specimens. The J-R curves determined from these tests were not valid per ASTM validity criteria so quantitative measures of the resistance to ductile crack initiation and growth were not obtained. These data suggests that standard fracture toughness tests were performed with small-scale DCT specimens may also not be valid.

  1. Combined macroscopic and microscopic approach to the fracture of metals. Technical progress report

    International Nuclear Information System (INIS)

    Asaro, R.J.; Gurland, J.; Needleman, A.; Rice, R.J.

    1979-06-01

    Progress is reported on microscopic fracture mechanisms, including studies of void and crack initiation in steels in the absence and presence of hydrogen, the effects of hydrogen on ductile fracture in medium and high carbon steels; elastic--plastic crack growth including the quasi-stable growth of cracks in ductile solids under increasing load and conditions of instability; and elevated temperature rupture including analysis of the stress field near a crack tip in an elastic-nonlinear viscous material under tensile load as well as the processes of diffusion, and cavitation of grain boundaries in plastically creeping materials

  2. Shoulder Fractures

    Science.gov (United States)

    ... as shown on an x-ray. Selection of treatment depends upon the patient’s activity level, the location of the fracture and the severity of the fracture. Recovery Shoulder fractures may leave a patient with permanent shoulder stiffness, regardless of ...

  3. Stress Fractures

    Science.gov (United States)

    Stress fractures Overview Stress fractures are tiny cracks in a bone. They're caused by repetitive force, often from overuse — such as repeatedly jumping up and down or running long distances. Stress fractures can also arise from normal use of ...

  4. Skull fracture

    Science.gov (United States)

    ... follow bicycle safety recommendations. Do not drink and drive. Do not allow yourself to be driven by someone who may have been drinking alcohol or is otherwise impaired. Alternative Names Basilar skull fracture; Depressed skull fracture; Linear skull fracture Images Skull of an adult Skull ...

  5. Application of rapid solidification powder metallurgy processing to prepare Cu–Al–Ni high temperature shape memory alloy strips with high strength and high ductility

    Energy Technology Data Exchange (ETDEWEB)

    Vajpai, S.K., E-mail: vajpaisk@gmail.com [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India); Dube, R.K., E-mail: rkd@iitk.ac.in [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India); Sangal, S., E-mail: sangals@iitk.ac.in [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India)

    2013-05-15

    Cu–Al–Ni high temperature shape memory alloy (HTSMA) strips were successfully prepared from rapid solidified water atomized Cu–Al–Ni pre-alloyed powders via hot densification rolling of unsheathed sintered powder preforms. Finished heat-treated Cu–Al–Ni alloy strips had fine-grained structure, average grain size approximately 16 μm, and exhibited a combination of high strength and high ductility. It has been demonstrated that the redistribution of nano-sized alumina particles, present on the surface as well as inside the starting water atomized Cu–Al–Ni pre-alloyed powder particles, due to plastic deformation of starting powder particles during hot densification rolling resulted in the fine grained microstructure in the finished SMA strips. The finished SMA strips were almost fully martensitic in nature, consisting of a mixture of β{sub 1}{sup ′} and γ{sub 1}{sup ′} martensite. The average fracture strength and fracture strain of the finished SMA strips were 810 MPa and 12%, respectively, and the fractured specimens exhibited primarily micro-void coalescence type ductile nature of fracture. Finished Cu–Al–Ni SMA strips exhibited high characteristic transformation temperatures and an almost 100% one-way shape recovery was obtained in the specimens up to 4% applied deformation pre-strain. The retained two-way shape memory recovery increased with increasing applied training pre-strain, achieving a maximum value of 16.25% at 5% applied training pre-strain.

  6. Brittle-ductile transition for nuclear applications in contact with mercury; Transition fragile - ductile des aciers pour des applications nucleaires en contact avec du mercure

    Energy Technology Data Exchange (ETDEWEB)

    Medina-Almazan, L.; Auger, T.; Gorse, D. [CECM/CNRS-UPR2801, 15 rue Georges Urbain, 94407 Vitry sur Seine CEDEX (France)

    2006-07-01

    In this work is studied the mercury embrittlement of austenitic stainless steel 316L and ferritic-martensitic steel T91 at ambient temperature in carrying out tensile tests on CCT (Center Cracked Tension) specimens at solicitation velocities between 1.67*10{sup -8} and 6.67*10{sup -3} m.s{sup -1}. The results reveal that these two steels are sensitive to mercury embrittlement. A ductile-brittle transition of the steel 316L in contact to mercury in terms of the deformation velocity is observed. The early beginnings of such a transition are visible too on the steel T91 in the experiment conditions. On a some range of the solicitation velocity, the presence of mercury modifies the plastic behaviour of the material in inhibiting the nucleation-growth of the cavities. For these two steels in contact with mercury, in the area of velocities for which a brittle rupture is observed, it appears that the fracture is produced by de-cohesion of shear bands. (O.M.)

  7. 49 CFR 192.489 - Remedial measures: Cast iron and ductile iron pipelines.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Remedial measures: Cast iron and ductile iron... for Corrosion Control § 192.489 Remedial measures: Cast iron and ductile iron pipelines. (a) General graphitization. Each segment of cast iron or ductile iron pipe on which general graphitization is found to a...

  8. 49 CFR 192.369 - Service lines: Connections to cast iron or ductile iron mains.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Service lines: Connections to cast iron or ductile... Customer Meters, Service Regulators, and Service Lines § 192.369 Service lines: Connections to cast iron or ductile iron mains. (a) Each service line connected to a cast iron or ductile iron main must be connected...

  9. Effect of ion irradiation on tensile ductility, strength and fictive temperature in metallic glass nanowires

    International Nuclear Information System (INIS)

    Magagnosc, D.J.; Kumar, G.; Schroers, J.; Felfer, P.; Cairney, J.M.; Gianola, D.S.

    2014-01-01

    Ion irradiation of thermoplastically molded Pt 57.5 Cu 14.3 Ni 5.7 P 22.5 metallic glass nanowires is used to study the relationship between glass structure and tensile behavior across a wide range of structural states. Starting with the as-molded state of the glass, ion fluence and irradiated volume fraction are systematically varied to rejuvenate the glass, and the resulting plastic behavior of the metallic glass nanowires probed by in situ mechanical testing in a scanning electron microscope. Whereas the as-molded nanowires exhibit high strength, brittle-like fracture and negligible inelastic deformation, ion-irradiated nanowires show tensile ductility and quasi-homogeneous plastic deformation. Signatures of changes to the glass structure owing to ion irradiation as obtained from electron diffraction are subtle, despite relatively large yield strength reductions of hundreds of megapascals relative to the as-molded condition. To reconcile changes in mechanical behavior with glass properties, we adapt previous models equating the released strain energy during shear banding to a transit through the glass transition temperature by incorporating the excess enthalpy associated with distinct structural states. Our model suggests that ion irradiation increases the fictive temperature of our glass by tens of degrees – the equivalent of many orders of magnitude change in cooling rate. We further show our analytical description of yield strength to quantitatively describe literature results showing a correlation between severe plastic deformation and hardness in a single glass system. Our results highlight not only the capacity for room temperature ductile plastic flow in nanoscaled metallic glasses, but also processing strategies capable of glass rejuvenation outside of the realm of traditional thermal treatments

  10. Cohesive stress heterogeneities and the transition from intrinsic ductility to brittleness

    Science.gov (United States)

    Tanguy, D.

    2017-11-01

    The influence of nanoscale cavities on the fracture of the Σ 33 {554 }[110 ] symmetrical tilt grain boundary is studied by atomistic simulations. The crack crystallography is chosen such that dislocation emission is easy. A transition from a ductile behavior of the tip to a brittle one is obtained for a dense (coverage beyond 15% and intercavity spacing smaller than 4 nm) distribution of small cavities (sizes in-between 1 and 2 nm). The results are in good agreement with recent experiments from the literature. Even at the highest coverage, the character of the crack is highly sensitive to the initial position of the tip and a mixture of ductile and brittle responses is found. This complexity is beyond the usual criterion based on the drop of the work of separation with the amount of damage in the structure. It is shown that a heterogeneous cohesive zone model, with parameters extracted from the simulations and enriched with a criterion for plasticity, can explain the simulations and reproduce the transition. Additional simulations show that outside this range of small sizes and dense packing, which gives essentially a two-dimensional response (either crack opening or infinite straight dislocation emission), dislocation half-loops appear for intercavity spacing starting at about 4 nm. They constitute, together with regions of low coverage/small cavities, efficient obstacles to brittle cracking. These results could be guidelines to designing interfaces more resistant to solute embrittlement, in general. The cohesive zone model is generic. Furthermore, the {554} single crystal was used to determine to which extent the results depend on the details of the core structure versus the cavity distribution. These elements show that the conclusions reached have a generic character.

  11. [Hip fractures].

    Science.gov (United States)

    Weisová, Drahomíra; Salášek, Martin; Pavelka, Tomáš

    2013-01-01

    Hip fractures are ranked among the frequent injuries. These fractures have been often coupled with high energy trauma in children and in patients with normal bone structure, low energy trauma and osteoporotic fracture (fragility fracture) is typical in elder patients. Hip fractures are divided into five groups: femoral head fracture, femoral neck fracture, pertrochanteric, intertrochateric and subtrochanteric fracture. Surgical treatment is indicated in all patients unless contraindications are present. Long bed rest has been accompanied by a high risk of development of thromboembolic disease, pneumonia and bed sore. Healing in the wrong position and nonunions are often the result of conservative treatment. Screw osteosynthesis is performed in isolated femoral head factures. Three cannulated screws or a DHS plate (dynamic hip screw) are used in fractures of the femoral neck with normal femoral head perfusion, total hip replacement is recommended in elder patients and in case of loss of blood supply of the femoral head. Pertrochanteric and intertrochanteric fractures can be stabilized by the femoral nails (PFN, PFN A, PFH - proximal femoral nail), nails are suitable for minimally invasive insertion and provide higher stability in the shaft, or plates (DHS) designed for stable pertronchanteric and intertrochanteric fractures. Subtrochanteric fractures can be fixed also intramedullary (nails - PFN long, PFN A long) and extramedullary (plates - DCS dynamic condylar screw, proximal femoral LCP - locking compression plate). Open reduction with internal plate fixation is advantageous for pathological fractures, as biopsy sampling can be performed. Hip fracture rehabilitation is integral part of the treatment, including walking on crutches or with a walker with partial weight bearing for at least six weeks.

  12. Effects Of 0.25 % Mo (Molybdenum Which Is Contained In The Ductile Cast Iron On Mechanical Properties Of Austempered Ductile Iron (ADI.

    Directory of Open Access Journals (Sweden)

    Nukman Nukman

    2010-10-01

    Full Text Available The aim of this research is to investigate the effects of 0.25 % Mo (Molybdenum which is contained in the ductile cast iron on mechanical properties of Austempered Ductile Iron (ADI. The various temperatures and the holding times are used in the heat treatment processes. Using a given 0.25 % Mo in the ductile iron, ADI's alloyed developes a higher ultimate tensile stress value and decreases the elongation if we compare with the as cast (non alloy ductile iron. The higher impact energy value obtained at 9000 C austenization and 375o C austempering temperatures during 60 minutes holding times. The structure changes into ausferrit.

  13. Acetabular Fracture

    Directory of Open Access Journals (Sweden)

    Chad Correa

    2017-09-01

    Full Text Available History of present illness: A 77-year-old female presented to her primary care physician (PCP with right hip pain after a mechanical fall. She did not lose consciousness or have any other traumatic injuries. She was unable to ambulate post-fall, so X-rays were ordered by her PCP. Her X-rays were concerning for a right acetabular fracture (see purple arrows, so the patient was referred to the emergency department where a computed tomography (CT scan was ordered. Significant findings: The non-contrast CT images show a minimally displaced comminuted fracture of the right acetabulum involving the acetabular roof, medial and anterior walls (red arrows, with associated obturator muscle hematoma (blue oval. Discussion: Acetabular fractures are quite rare. There are 37 pelvic fractures per 100,000 people in the United States annually, and only 10% of these involve the acetabulum. They occur more frequently in the elderly totaling an estimated 4,000 per year. High-energy trauma is the primary cause of acetabular fractures in younger individuals and these fractures are commonly associated with other fractures and pelvic ring disruptions. Fractures secondary to moderate or minimal trauma are increasingly of concern in patients of advanced age.1 Classification of acetabular fractures can be challenging. However, the approach can be simplified by remembering the three basic types of acetabular fractures (column, transverse, and wall and their corresponding radiologic views. First, column fractures should be evaluated with coronally oriented CT images. This type of fracture demonstrates a coronal fracture line running caudad to craniad, essentially breaking the acetabulum into two halves: a front half and a back half. Secondly, transverse fractures should be evaluated by sagittally oriented CT images. By definition, a transverse fracture separates the acetabulum into superior and inferior halves with the fracture line extending from anterior to posterior

  14. Simulations of ductile flow in brittle material processing

    Energy Technology Data Exchange (ETDEWEB)

    Luh, M.H.; Strenkowski, J.S.

    1988-12-01

    Research is continuing on the effects of thermal properties of the cutting tool and workpiece on the overall temperature distribution. Using an Eulerian finite element model, diamond and steel tools cutting aluminum have been simulated at various, speeds, and depths of cut. The relative magnitude of the thermal conductivity of the tool and the workpiece is believed to be a primary factor in the resulting temperature distribution in the workpiece. This effect is demonstrated in the change of maximum surface temperatures for diamond on aluminum vs. steel on aluminum. As a preliminary step toward the study of ductile flow in brittle materials, the relative thermal conductivities of diamond on polycarbonate is simulated. In this case, the maximum temperature shifts from the rake face of the tool to the surface of the machined workpiece, thus promoting ductile flow in the workpiece surface.

  15. Ductile-brittle transition in transverse isotropic fibrous networks

    Science.gov (United States)

    Luo, Guoquan; Shi, Liping; Li, Mingwei; Zhong, Yesheng; He, Xiaodong; Wang, Jiazhi

    2018-01-01

    Anisotropic fibrous networks, especially transverse isotropic fibrous networks, are widely used to model the microstructures of biological tissues, polymer gels, fibrous thermal insulations, and other fibrous materials. In this letter, we build a three-dimensional transverse isotropic fibrous network model and study its mechanical properties along the through-thickness direction. We propose a measurement of anisotropy for transverse isotropic fibrous networks and then study the influence of anisotropy on the networks' mechanical properties, including its elastic modulus, maximum elongation, and stress-strain curve, by means of finite-element simulation. We also study theoretically the influence of anisotropy on maximum elongation. We find that as the anisotropy of the networks becomes stronger, the elastic modulus decreases and the maximum elongation increases, indicating a transition in mechanical properties from brittle to ductile. We identify this transition as the "ductile-brittle transition." This transition can help guide the design and regulate the mechanical properties of a transverse isotropic fibrous network.

  16. Modification of evaluation response spectrum by ductility of equipment anchorage

    International Nuclear Information System (INIS)

    Choi, I. G.; Jun, Y. S.; Su, J. M.

    2003-01-01

    The failure mode of welded anchorage is assumed as brittle in the seismic capacity evaluation of nuclear power plant equipments. But the welded anchorage has some ductile capacity. This limited displacement capacity can cause the reduction of the effective frequency of high frequency equipments and the increase of the inelastic energy absorption capacity due to the nonlinear behavior. In this study, the uniform hazard spectrum for Korean nuclear power plant site was modified using the response spectrum reduction factor developed by EPRI. The spectral acceleration for various damping ratio was determined by the theoretical method based on the random vibration theory. In conclusion, the high frequency components of evaluation response spectra were greatly reduced due to the consideration of welded anchorage ductility. This reduced response spectra can be used for the development of in-structure response spectra used in the seismic capacity evaluation of high frequency equipments

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-31

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

  18. Limits to ductility set by plastic flow localization

    International Nuclear Information System (INIS)

    Needleman, A.; Rice, J.R.

    1977-11-01

    The theory of strain localization is reviewed with reference both to local necking in sheet metal forming processes and to more general three dimensional shear band localizations that sometimes mark the onset of ductile rupture. Both bifurcation behavior and the growth of initial imperfections are considered. In addition to analyses based on classical Mises-like constitutive laws, approaches to localization based on constitutive models that may more accurately model processes of slip and progressive rupturing on the microscale in structural alloys are discussed. Among these non-classical constitutive features are the destabilizing roles of yield surface vertices and of non-normality effects, arising, for example, from slight pressure sensitivity of yield. Analyses based on a constitutive model of a progressively cavitating dilational plastic material which is intended to model the process of ductile void growth in metals are also discussed. A variety of numerical results are presented. In the context of the three dimensional theory of localization, it is shown that a simple vertex model predicts ratios of ductility in plane strain tension to ductility in axisymmetric tension qualitatively consistent with experiment, and the destabilizing influence of a hydrostatic stress dependent void nucleation criterion is illustrated. In the sheet necking context, and focussing on positive biaxial stretching, it is shown that forming limit curves based on a simple vertex model and those based on a simple void growth model are qualitatively in accord, although attributing instability to very different physical mechanisms. These forming limit curves are compared with those obtained from the Mises material model and employing various material and geometric imperfections

  19. Solidification and microstructure of thin walled ductile cast iron

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin

    2006-01-01

    In the recent years there has been an increasing interest in light constructions in order to save weight in e.g. cars. Ductile cast iron has good mechanical properties but it is necessary to re­duce the wall thicknesses of the castings in order to reduce the weight. Reducing the wall thicknesses...... of the casting will increase the cooling rates and by that change the conditions for nucleation and growth during solidification....

  20. Adhesion and wear properties of boro-tempered ductile iron

    International Nuclear Information System (INIS)

    Kayali, Yusuf; Yalcin, Yilmaz; Taktak, Suekrue

    2011-01-01

    Highlights: → In this study, the wear and adhesion properties of BDI were investigated. → Boro-tempering process under several heat treatment conditions was examined. → Optical microscope, SEM and XRD analysis were carried out to investigate the microstructure. → It was observed that boro-tempering process improves micro-hardness and wear properties of ductile irons. -- Abstract: In this study, adhesion and wear properties of boro-tempered ductile iron (BDI) were investigated. Boro-tempering was carried out on two stage processes i.e. boronizing and tempering. At the first stage, ductile iron samples were boronized by using pack process at 900 o C for 1, 3, and 5 h and then, secondly tempered at 250, 300, 350, and 400 o C for 1 h. X-ray diffraction (XRD) analysis of boro-tempered samples showed that FeB and Fe 2 B phases were found on the surface of the samples. The Daimler-Benz Rockwell-C adhesion test was used to assess the adhesion of boride layer. Test result showed that adhesion decreased with increasing boriding time and increased with increasing tempering temperature. Dry sliding wear tests of these samples were performed against Al 2 O 3 ball at a constant sliding speed and loads of 5 and 10 N. Wear tests indicated that boro-tempering heat treatment increased wear resistance of ductile iron. In addition, it was found that while wear rate of boro-tempered samples decreased with increasing boriding time, there is no significant affect of tempering temperature on wear rate.

  1. Microstructural characteristics of Al-alloyed austempered ductile irons

    International Nuclear Information System (INIS)

    Kiani-Rashid, A.R.; Edmonds, D.V.

    2009-01-01

    Microstructural development after austempering ductile irons containing 0.48% and 4.88%Al has been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental irons were made by green sand casting and gravity die casting. After austenitising at 920 deg. C for 90 min, an austempering treatment at 400 deg. C for times up to 100 min resulted in microstructures consisting of carbide-free bainitic ferrite with considerable amounts of high carbon retained austenite.

  2. Wear Behavior of Austempered Ductile Iron with Nanosized Additives

    Directory of Open Access Journals (Sweden)

    J. Kaleicheva

    2014-03-01

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

  3. Production of austempered ductile iron gears for transmission cases

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-07-01

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

  4. Casting Ductile Iron in Layer Moulds Made from Ecological Sands

    Directory of Open Access Journals (Sweden)

    M. Rączka

    2012-09-01

    Full Text Available The article contains the results of tests performed under the target project in Hardtop Foundry Charsznica.The objective of the tests and studies was to develop a technology of making high-quality ductile iron castings, combined witheffective means of environmental protection. The studies presented in this article related to castings weighing from 1 to 300 kg made from ductile iron of grades 400-15 and 500-7, using two-layer moulds, where the facing and core sand was the sand with an alkaline organic binder, while backing sand was the sand with an inorganic geopolymer binder.A simplified method of sand reclamation was applied with possible reuse of the reclaim as an addition to the backing sand. The castiron spheroidising treatment and inoculation were selected taking into account the specific conditions of Hardtop Foundry. A pilot batch of castings was made, testing the gating and feeding systems and using exothermic sleeves on risers. The study confirmed the validity of the adopted concept of making ductile iron castings in layer moulds, while maintaining the content of sand with an organic binder at a level of maximum 15%.

  5. Modeling combined tension-shear failure of ductile materials

    International Nuclear Information System (INIS)

    Partom, Y

    2014-01-01

    Failure of ductile materials is usually expressed in terms of effective plastic strain. Ductile materials can fail by two different failure modes, shear failure and tensile failure. Under dynamic loading shear failure has to do with shear localization and formation of adiabatic shear bands. In these bands plastic strain rate is very high, dissipative heating is extensive, and shear strength is lost. Shear localization starts at a certain value of effective plastic strain, when thermal softening overcomes strain hardening. Shear failure is therefore represented in terms of effective plastic strain. On the other hand, tensile failure comes about by void growth under tension. For voids in a tension field there is a threshold state of the remote field for which voids grow spontaneously (cavitation), and the material there fails. Cavitation depends on the remote field stress components and on the flow stress. In this way failure in tension is related to shear strength and to failure in shear. Here we first evaluate the cavitation threshold for different remote field situations, using 2D numerical simulations with a hydro code. We then use the results to compute examples of rate dependent tension-shear failure of a ductile material.

  6. Development of stiffer and ductile glulam portal frame

    Science.gov (United States)

    Komatsu, Kohei

    2017-11-01

    Portal frame structures, which are constituted of straight glulam beams and columns connected semi-rigidly by steel insert gusset plate with a lot of drift pins, were the first successful glulam structures widely used in Japan. In addition to this connection system, the author invented also a new type of jointing devise for glulam structures named as "Lagscrewbolt" which had a full threaded portion at inner part to grip wooden member as well as another thread part at the end of shank to connect with other member. The initial type of "Lagscrewbolt" was successfully applied to a various types of glulam buildings which could be rapidly built-up on construction site. Its strength performance, however, was rather brittle therefore the improvement of the ductility was a crucial research subject. In order to give a sufficient ductility on the "Lagscrewbolted joint system", so-called "Slotted Bolted Connection" concept was adopted for making use of large energy dissipation characteristics due to high-tension bolted steel connection with slotted bolt holes. Static & dynamic performance of glulam portal frame specimens was evaluated by static cyclic loading test as well as shaking table test. Current latest form of the jointing system can show very high ductility as well as stable hysteretic cyclic loops by inserting brass-shim between steel-to-steel friction interfaces

  7. Colles Fracture

    OpenAIRE

    Sánchez León, Belisario

    2014-01-01

    Our expertise is the study of more than 2,000 cases of Colles' fractures. Colles name should in this case to synthesize the type of fractures of the lower end of the radius. There have been various proposed classifications according to the different fracture lines can be demonstrated radiologically in the region of the wrist. We believe that these ratings should only be retained if the concept of the articular fracture or not in the classical sense, since it has great value in the functional ...

  8. [Calcaneus fractures].

    Science.gov (United States)

    Clare, M P; Sanders, R W

    2011-10-01

    Fractures of the calcaneus generally occur in the setting of high-energy trauma, resulting in complex, three-dimensionally oriented fracture patterns. Surgical treatment is typically indicated for displaced intra-articular fractures, permitting restoration of calcaneal height, width and overall morphology, in addition to the posterior facet articular surface where possible, and enabling late in situ arthrodesis as a means of salvage in the event of post-traumatic arthritis. The present article briefly discusses our preferred methods for the management of calcaneal fractures. An English full text version of this article is available at SpringerLink as supplemental.

  9. Fracture behavior of quenched poly(lactic acid

    Directory of Open Access Journals (Sweden)

    2011-01-01

    Full Text Available The effect of a quenching treatment applied on heated cast sheet extruded films of two poly(lactic acid (PLA commercial grades, with different optical purities, was studied. The thermal and mechanical properties of the films, as well as their fracture behavior, were assessed by differential scanning calorimetry (DSC, tensile tests, and the essential work of fracture (EWF approach. The heating-quenching treatment causes a de-aging effect with an increase in the free volume of polymer chains evidenced by a decrease in the glass transition temperature (Tg and a decrease in the tensile stiffness and yield stress. As a result, there is an abrupt increase in ductility, finding a dramatic change in the fracture behavior, from brittle to ductile. The use of digital image correlation (DIC of the strain field analysis during fracture testing has allowed relating the decrease on the yield stress promoted by quenching with the crack propagation kinetics. The use of the EWF method to characterize the fracture toughness of PLA has allowed to measure this enhancement on toughness, finding that the specific essential work of fracture (we and the plastic term (βwp parameters increased 120% and 1200%, respectively, after the quenching process.

  10. 49 CFR 192.487 - Remedial measures: Distribution lines other than cast iron or ductile iron lines.

    Science.gov (United States)

    2010-10-01

    ... cast iron or ductile iron lines. 192.487 Section 192.487 Transportation Other Regulations Relating to... iron or ductile iron lines. (a) General corrosion. Except for cast iron or ductile iron pipe, each... the purpose of this paragraph. (b) Localized corrosion pitting. Except for cast iron or ductile iron...

  11. Use of Circumferentially Cracked Bar sample for CTOD fracture toughness determination in the upper shelf regime

    Directory of Open Access Journals (Sweden)

    D. Gentile

    2014-10-01

    Full Text Available In this work, the use of circumferentially cracked bar (CCB sample to determine material fracture toughness in the upper shelf regime for carbon steels has been investigated. Since high fracture toughness materials are known to exhibit extensive crack tip blunting before ductile crack initiation, accurate specimen design is required to provide realistic fracture toughness measurement. Here, a CCB was designed to have similar loss of constraint as for SENT sample. Continuum damage mechanics was used to predict the occurrence of ductile crack initiation and propagation. Finite element analysis was performed to predict specimen response and to compare computed J-integral crack driving force with measured CTOD. Finally, experimental tests were performed on X65 carbon steel and the measured critical CTOD was compared with available fracture data obtained with SENT.

  12. Tensile and fracture properties of EBR-II-irradiated V-15Cr-5Ti containing helium

    Energy Technology Data Exchange (ETDEWEB)

    Grossbeck, M.L.; Horak, J.A.

    1986-01-01

    The alloy V-15Cr-5Ti was cyclotron-implanted with 80 appM He and subsequently irradiated in the Experimental Breeder Reactor (EBR-II) to 30 dpa. The same alloy was also irradiated in the 10, 20, and 30% cold-worked conditions. Irradiation temperatures ranged from 400 to 700/sup 0/C. No significant effects of helium on mechanical properties were found in this temperature range although the neutron irradiation shifted the temperature of transition from cleavage to ductile fracture to about 625/sup 0/C. Ten percent cold work was found to have a beneficial effect in reducing the tendency for cleavage fracture following irradiation, but high levels (20%) were observed to reduce ductility. Still higher levels (30%) improved ductility by inducing recovery during the elevated-temperature irradiation. Swelling was found to be negligible, but precipitates - titanium oxides or carbonitrides - contained substantial cavities.

  13. Tensile and fracture properties of EBR-II-irradiated V-15Cr-5Ti containing helium

    International Nuclear Information System (INIS)

    Grossbeck, M.L.; Horak, J.A.

    1986-01-01

    The alloy V-15Cr-5Ti was cyclotron-implanted with 80 appM He and subsequently irradiated in the Experimental Breeder Reactor (EBR-II) to 30 dpa. The same alloy was also irradiated in the 10, 20, and 30% cold-worked conditions. Irradiation temperatures ranged from 400 to 700 0 C. No significant effects of helium on mechanical properties were found in this temperature range although the neutron irradiation shifted the temperature of transition from cleavage to ductile fracture to about 625 0 C. Ten percent cold work was found to have a beneficial effect in reducing the tendency for cleavage fracture following irradiation, but high levels (20%) were observed to reduce ductility. Still higher levels (30%) improved ductility by inducing recovery during the elevated-temperature irradiation. Swelling was found to be negligible, but precipitates - titanium oxides or carbonitrides - contained substantial cavities

  14. Ductile and brittle structural evolution of the Laxemar-Simpevarp area: an independent analysis based on local and regional constraints

    International Nuclear Information System (INIS)

    Viola, Giulio

    2008-10-01

    This report discusses the main aspects of the ductile and brittle deformational evolution of the Laxemar-Simpevarp area. Based on the interpretation of existing potential field geophysical data, it is suggested that the structural ductile grain of the region is controlled by large, c. EW trending shear zones with an overall sinistral strike-slip kinematics. The Oskarshamn Shear Zone (OSZ) and the Mederhult lineament are two examples of these shear zones and it is proposed that the ductile lineaments mapped in Laxemar-Simpevarp are genetically linked to shearing accommodated by these shear zones. The structural interpretation of the geophysical imagery of the Laxemar-Simpevarp regional model area and the available meso-scale structural information indicate that the Laxemar-Simpevarp study area can be interpreted as the analogue of a large-scale S/C' structural pattern. In detail, the Aespoe shear zone and other similarly oriented ductile shears represent C' shear bands that deform sinistrally the intervening EW lineaments (the S surfaces), which locally are significantly crenulated/folded in response to their asymptotic bending into the C' shears. This geometric and kinematic interpretation implies that, in contrast to existing reconstructions and models, EW- and not NE-trending shear zones become the main structural ductile feature of the region. Shear forces acting parallel to these main zones can successfully explain all the ductile structures described and reported from the area. The greatest compressive stress at the time of ductile shearing would trend NE-SW. The brittle deformation history of the region is complex and results from the multiple reactivation of fracture- and fault sets caused by the many orogenic episodes that affected the area during 1.5 Gyr of geological brittle evolution. Fault-slip data from outcrops and oriented drill cores were used to compute paleo-stress states. In the general absence of time markers that help constrain the relative

  15. Ductile and brittle structural evolution of the Laxemar-Simpevarp area: an independent analysis based on local and regional constraints

    Energy Technology Data Exchange (ETDEWEB)

    Viola, Giulio (Geological Survey of Norway, Trondheim (Norway))

    2008-10-15

    This report discusses the main aspects of the ductile and brittle deformational evolution of the Laxemar-Simpevarp area. Based on the interpretation of existing potential field geophysical data, it is suggested that the structural ductile grain of the region is controlled by large, c. EW trending shear zones with an overall sinistral strike-slip kinematics. The Oskarshamn Shear Zone (OSZ) and the Mederhult lineament are two examples of these shear zones and it is proposed that the ductile lineaments mapped in Laxemar-Simpevarp are genetically linked to shearing accommodated by these shear zones. The structural interpretation of the geophysical imagery of the Laxemar-Simpevarp regional model area and the available meso-scale structural information indicate that the Laxemar-Simpevarp study area can be interpreted as the analogue of a large-scale S/C' structural pattern. In detail, the Aespoe shear zone and other similarly oriented ductile shears represent C' shear bands that deform sinistrally the intervening EW lineaments (the S surfaces), which locally are significantly crenulated/folded in response to their asymptotic bending into the C' shears. This geometric and kinematic interpretation implies that, in contrast to existing reconstructions and models, EW- and not NE-trending shear zones become the main structural ductile feature of the region. Shear forces acting parallel to these main zones can successfully explain all the ductile structures described and reported from the area. The greatest compressive stress at the time of ductile shearing would trend NE-SW. The brittle deformation history of the region is complex and results from the multiple reactivation of fracture- and fault sets caused by the many orogenic episodes that affected the area during 1.5 Gyr of geological brittle evolution. Fault-slip data from outcrops and oriented drill cores were used to compute paleo-stress states. In the general absence of time markers that help constrain

  16. Intercritical heat treatments in ductile iron and steel

    Science.gov (United States)

    Aristizabal, Ricardo E.

    Materials such as dual phase (DP) steels, transformation induced plasticity (TRIP) steels and dual phase ductile irons are produced by intercritical heat treatments. These materials can provide significant weight savings in the automotive industry. The goal of this dissertation is to study intercritical heat treatments in ductile iron and steel to optimize the production parameters. Three different aspects were addressed. First, common steels were intercritically austenitized and austempered (intercritically austempered) under a variety conditions. The results showed that common grade steels that were intercritically austempered exhibited tensile properties in the same range as DP and TRIP steels. The second study consisted of determining the effect of heat treatment conditions on the tensile properties of intercritically austenitized, quenched and tempered ductile iron (IAQ&TDI). The results showed that (1) ultimate tensile strength (UTS) and yield strength (YS) were determined by the volume fraction of martensite, (2) tempering improved the elongation 1.7-2.5 times with only a slight decrease in strength, (3) the carbon in austenite formed during the intercritical heat treatment of ductile iron with a ferritic-pearlitic matrix came from the carbon available in the matrix and that carbon diffusion from the graphite nodules was restricted, and (4) limited segregation of substitutional elements occurred during intercritical austenitizing. Finally, intercritically austempered ductile iron (IADI) alloyed with different amounts of manganese and nickel was produced. Tensile properties and microstructure were determined. Also, the stability of the austenite during deformation and the lattice strains of the ferrite and the austenite phases were determined using x-ray diffraction (XRD) and neutron diffraction. The results indicated that: 1) high manganese concentrations produced materials with large blocky, low carbon austenite particles at the intercellular boundaries

  17. Advance of the perihelion of Mercury deduced from QFT

    Science.gov (United States)

    Chen, Shao-Guang

    I deduce the new gravitational formula from the variance in mass of QFT and GR (H05-0029-08, E15-0039 -08, E14-0032-08, D31-0054-10) in the partial differential: f (QFT) = f (GR) = delta∂ (m v)/delta∂ t = f _{P} + f _{C} , f _{P} = m delta∂ v / delta∂ t = - ( G m M /r (2) ) r / r, f _{C} = v delta∂ m / delta∂ t = - ( G m M / r (2) ) v / c (1), f (QFT) is the quasi-Casimir pressure of net virtual neutrinos nuν _{0} flux (after counteract contrary direction nuν _{0}). f (GR) is equivalent to Einstein’s equation, Eq. (1) is a new version of GR and can be solved exactly. Its core content is that the gravity produced by particles collide cannot linear addition, i.e., the nonlinearity of Einstein equation had been replaced by the nonlinearity caused by the variable mass in Eq.(1). Einstein equation can be inferred from Eq.(1) thereby from QFT, but QFT cannot be inferred from Eq.(1) or GR. f (QFT) is essential but f (GR) is phenomenological. Eq.(1) is obtained just by to absorb the essence of corpuscule collided gravitation origin ism proposed by Fatio in 1690 and 1920 Majorana’s experiment concept about gravitational shield effect again fuse with QFT. In my paper ‘QFT’S advance of the perihelion of Mercury, China Science &Technology Overview 125 88-90 (2011)’ QFT gravitational potential U = - G M /r is just the distribution density of net nuν _{0} flux, from SR we again get that: f (QFT) = f _{P} + f _{C}, f _{P} = - m ( delta∂ U / delta∂ r) r / r, f _{C} = - m ( delta∂U / delta∂ r) v / c (2), f _{ P} correspond the change rate of three-dimensional momentum p, f _{C} correspond the change rate of fourth dimensional momentum i m c which show directly as a dissipative force of mass change. According to Eq.(2) the circular motion is instability and elliptic motion is in the auto-stability state. In the fluctuation vacuum a particle with mass M neighbor another particle with mass m, the renormalization mass M and m will be less than that when

  18. Facial Fractures.

    Science.gov (United States)

    Ghosh, Rajarshi; Gopalkrishnan, Kulandaswamy

    2018-01-29

    The aim of this study is to retrospectively analyze the incidence of facial fractures along with age, gender predilection, etiology, commonest site, associated dental injuries, and any complications of patients operated in Craniofacial Unit of SDM College of Dental Sciences and Hospital. This retrospective study was conducted at the Department of OMFS, SDM College of Dental Sciences, Dharwad from January 2003 to December 2013. Data were recorded for the cause of injury, age and gender distribution, frequency and type of injury, localization and frequency of soft tissue injuries, dentoalveolar trauma, facial bone fractures, complications, concomitant injuries, and different treatment protocols.All the data were analyzed using statistical analysis that is chi-squared test. A total of 1146 patients reported at our unit with facial fractures during these 10 years. Males accounted for a higher frequency of facial fractures (88.8%). Mandible was the commonest bone to be fractured among all the facial bones (71.2%). Maxillary central incisors were the most common teeth to be injured (33.8%) and avulsion was the most common type of injury (44.6%). Commonest postoperative complication was plate infection (11%) leading to plate removal. Other injuries associated with facial fractures were rib fractures, head injuries, upper and lower limb fractures, etc., among these rib fractures were seen most frequently (21.6%). This study was performed to compare the different etiologic factors leading to diverse facial fracture patterns. By statistical analysis of this record the authors come to know about the relationship of facial fractures with gender, age, associated comorbidities, etc.

  19. Fracture toughness of stainless steel welds

    International Nuclear Information System (INIS)

    Mills, W.J.

    1985-11-01

    The effects of temperature, composition and weld-process variations on the fracture toughness behavior for Types 308 and 16-8-2 stainless steel (SS) welds were examined using the multiple-specimen J/sub R/-curve procedure. Fracture characteristics were found to be dependent on temperature and weld process but not on filler material. Gas-tungsten-arc (GTA) welds exhibited the highest fracture toughness, a shielded metal-arc (SMA) weld exhibited an intermediate toughness and submerged-arc (SA) welds yielded the lowest toughness. Minimum-expected fracture properties were defined from lower-bound J/sub c/ and tearing modulus values generated here and in previous studies. Fractographic examination revealed that microvoid coalescence was the operative fracture mechanism for all welds. Second phase particles of manganese silicide were found to be detrimental to the ductile fracture behavior because they separated from the matrix during the initial stages of plastic straining. In SA welds, the high density of inclusions resulting from silicon pickup from the flux promoted premature dimple rupture. The weld produced by the SMA process contained substantially less manganese silicide, while GTA welds contained no silicide inclusions. Delta ferrite particles present in all welds were substantially more resistant to local failure than the silicide phase. In welds containing little or no manganese silicide, delta ferrite particles initiated microvoid coalescence but only after extensive plastic straining

  20. Fracture sacrum.

    Directory of Open Access Journals (Sweden)

    Dogra A

    1995-04-01

    Full Text Available An extremely rare case of combined transverse and vertical fracture of sacrum with neurological deficit is reported here with a six month follow-up. The patient also had an L1 compression fracture. The patient has recovered significantly with conservative management.

  1. Elbow Fractures

    Science.gov (United States)

    ... occur commonly in children and in the elderly. Nerve and/or artery injuries can be associated with these types of fractures and must be carefully evaluated by your doctor. These fractures usually require surgical repair with plates and/or screw, unless they are ...

  2. Fracture and toughening of high volume fraction ceramic particle reinforced metals

    OpenAIRE

    Miserez, Ali Gilles Tchenguise

    2003-01-01

    This work contributes to the fundamental understanding of fracture properties of Particle Reinforced Metal Matrix Composites (PRMMCs), by identifying the key microstructural parameters that control fracture. To this end, PRMMCs with a high volume fraction of ceramic reinforcement (40-60 vol.%) are produced by gas-pressure infiltration. These composites are considered as model ductile/brittle twophase materials in that (i): the particles are homogeneously distributed in the matrix, (ii): the m...

  3. Fracture and toughening of high volume fraction ceramic particle reinforced metals

    OpenAIRE

    Miserez, Ali Gilles Tchenguise; Mortensen, Andreas

    2005-01-01

    This work contributes to the fundamental understanding of fracture properties of Particle Reinforced Metal Matrix Composites (PRMMCs), by identifying the key microstructural parameters that control fracture. To this end, PRMMCs with a high volume fraction of ceramic reinforcement (40-60 vol.%) are produced by gas-pressure infiltration. These composites are considered as model ductile/brittle twophase materials in that (i): the particles are homogeneously distributed in the matrix, (ii): the m...

  4. Fracture Mechanics

    CERN Document Server

    Zehnder, Alan T

    2012-01-01

    Fracture mechanics is a vast and growing field. This book develops the basic elements needed for both fracture research and engineering practice. The emphasis is on continuum mechanics models for energy flows and crack-tip stress- and deformation fields in elastic and elastic-plastic materials. In addition to a brief discussion of computational fracture methods, the text includes practical sections on fracture criteria, fracture toughness testing, and methods for measuring stress intensity factors and energy release rates. Class-tested at Cornell, this book is designed for students, researchers and practitioners interested in understanding and contributing to a diverse and vital field of knowledge. Alan Zehnder joined the faculty at Cornell University in 1988. Since then he has served in a number of leadership roles including Chair of the Department of Theoretical and Applied Mechanics, and Director of the Sibley School of Mechanical and Aerospace Engineering.  He teaches applied mechanics and his research t...

  5. Future trends in fracture mechanics: theory and applications

    International Nuclear Information System (INIS)

    Hosbons, R.R.

    1978-05-01

    A brief description of the current methods available for the analysis of fracture in ductile materials is given. Crack-opening displacement, R-curves and J-integrals are discussed and their future incorporation into structural codes assessed. The current areas of research which will probably influence code making bodies are also described. Emphasis is made on J-integral theory and a description of its limitations and extensions. Numerical techniques for calculating J for complicated structure are outlined. (author)

  6. Fracture of metal foams : In-situ testing and numerical modeling

    NARCIS (Netherlands)

    Onck, P.R.; van Merkerk, R.; de Hosson, J.T.M.; Schmidt, I

    This paper is on a combined experimental/modeling study on the tensile fracture of open-cell foams. In-situ tensile tests show that individual struts can fail in a brittle or ductile mode, presumably depending on the presence of casting defects. In-situ single strut tests were performed, enabling

  7. Mechanical properties and fracture features of low-activation ferritic-martensitic steel EK-181 at subzero temperatures

    Science.gov (United States)

    Polekhina, N. A.; Litovchenko, I. Yu.; Tyumentsev, A. N.; Kravchenko, D. A.; Chernov, V. M.; Leontyeva-Smirnova, M. V.

    2017-12-01

    The short-term strength and plastic properties of ferritic-martensitic steel EK-181, as well as the features of its plastic deformation and fracture in the temperature range from 20 to -196°C are investigated by an active tensile deformation method. A significant increase in the temperature dependence of the steel yield strength in the interval of the ductile-to-brittle transition is observed. No qualitative changes in the fracture pattern of the samples are revealed in the region of this interval. The fractograms taken after deformation at several temperatures differ only in the relative fractions of the ductile and brittle components.

  8. Atomistic Origin of Brittle Failure of Boron Carbide from Large-Scale Reactive Dynamics Simulations: Suggestions toward Improved Ductility.

    Science.gov (United States)

    An, Qi; Goddard, William A

    2015-09-04

    Ceramics are strong, but their low fracture toughness prevents extended engineering applications. In particular, boron carbide (B(4)C), the third hardest material in nature, has not been incorporated into many commercial applications because it exhibits anomalous failure when subjected to hypervelocity impact. To determine the atomistic origin of this brittle failure, we performed large-scale (∼200,000  atoms/cell) reactive-molecular-dynamics simulations of shear deformations of B(4)C, using the quantum-mechanics-derived reactive force field simulation. We examined the (0001)/⟨101̅0⟩ slip system related to deformation twinning and the (011̅1̅)/⟨1̅101⟩ slip system related to amorphous band formation. We find that brittle failure in B(4)C arises from formation of higher density amorphous bands due to fracture of the icosahedra, a unique feature of these boron based materials. This leads to negative pressure and cavitation resulting in crack opening. Thus, to design ductile materials based on B(4)C we propose alloying aimed at promoting shear relaxation through intericosahedral slip that avoids icosahedral fracture.

  9. Analysis Of Hydro Formed Complex Shape Parts Using A Ductile Fracture Criterion

    Science.gov (United States)

    Palumbo, G.; Pinto, S.; Sorgente, D.; Tricarico, L.

    2004-06-01

    Nowadays the Hydro Forming techniques have been largely accepted by industries for the production of components characterized by complex shape, good surface quality, near net shape and low volume batch. In particular the Sheet Hydro Forming (SHF) process offers the possibility of no restrictions in the final shape of the part. This is the reason why a deeper investigation on the chance of using the SHF process for the production of complex shaped parts could be of great interest. In this work, the authors have considered as case of study a compound part which is made of a cylindrical region (the base) connected to a square part (the protrusion). Experimental and numerical activities have been performed. In particular, a commercial Finite Element (FE) code has been chosen to simulate the SHF process; a stress-strain based damage variable according to the Oh's criterion (derived from the Cockroft and Latham one) has been also used to evaluate the process limits. The Critical Damage Value (CDV) of the steel adopted for the analysis (AISI 304) has been set using experimental test results. The critical regions and the blank thinning have been analyzed for different geometrical configurations of the compound die cavity. Thus, a complexity shape factor has been defined.

  10. Predictions of mixed mode interface crack growth using a cohesive zone model for ductile fracture

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2004-01-01

    with the surrounding material in the tangential direction. Thus, the present interface description incorporates the important effect of stress triaxiality on damage evolution, which is not part of the usual cohesive zone models. The interface elements have been used previously for mode I loading conditions...

  11. Effects of bending and heat on the ductility and fracture toughness of flange plate.

    Science.gov (United States)

    2012-05-01

    Bridge fabricators for the Texas Department of Transportation (TxDOT) have occasionally experienced the : formation of cracks in flange plate during bending operations, particularly when heat is applied. Bending the : flange plate is necessary for ce...

  12. Ductility of Individual Trabeculae as a Measurement of Bone Quality to Predict Risk of Fracture

    Data.gov (United States)

    National Aeronautics and Space Administration — The success and safety of future human spaceflight exploration must overcome the physiological challenges of long exposure to reduced gravity environments. Research...

  13. Standard test method for conducting drop-weight test to determine nil-ductility transition temperature of ferritic steels

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2006-01-01

    1.1 This test method covers the determination of the nil-ductility transition (NDT) temperature of ferritic steels, 5/8 in. (15.9 mm) and thicker. 1.2 This test method may be used whenever the inquiry, contract, order, or specification states that the steels are subject to fracture toughness requirements as determined by the drop-weight test. 1.3 The values stated in inch-pound units are to be regarded as the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  14. On the ductile-to-brittle transition behavior of martensitic alloys neutron irradiated to 26 dpa

    International Nuclear Information System (INIS)

    Hu, W.L.; Gelles, D.S.

    1987-01-01

    Charpy impact tests were conducted on specimens made of HT-9 and 9Cr-1Mo in various heat treatment conditions which were irradiated in EBR-II to 26 dpa at 390 to 500 0 C. The results are compared with previous results on specimens irradiated to 13 dpa. HT-9 base metal irradiated at low temperatures showed a small additional increase in ductile brittle transition temperature and a decrease in upper shelf energy from 13 to 26 dpa. No fluence effect was observed in 9Cr-1Mo base metal. The 9Cr-1Mo weldment showed degraded DBTT but improved USE response compared to base metal, contrary to previous findings on HT-9. Significant differences were observed in HT-9 base metal between mill annealed material and normalized and tempered material. The highest DBTT for HT-9 alloys was 50 0 C higher than for the worst case in 9Cr-1Mo alloys. Fractography and hardness measurements were also obtained. Significant differences in fracture appearance were observed in different product forms, although no dependence on fluence was observed. Failure was controlled by the preirradiation microstructure

  15. Effects of Hydride Rim on Ductility of Zircaloy-4 using Ring Compression Test

    Energy Technology Data Exchange (ETDEWEB)

    Kang, So-Young; Kim, Ho-A; Lee, Ji-Min; Kim, Yong-Soo [Hanyang University, Seoul (Korea, Republic of)

    2016-10-15

    The objective of this preliminary study is to form hydride rim around the cladding outside wall typically observed for high burnup fuel cladding. In addition, ring compression test (RCT) that simulates pinch-type loading subjected to cladding during SNF transportation is conducted to investigate separate effects of hydride rim on mechanical properties of the cladding. In this preliminary study, in order to simulate high burnup fuel cladding, hydride rim was attempted to form around the cladding outside wall. Encapsulated 150 mm long Zircaloy-4 tube which was plated with nickel at outer surface was used and then it charged with hydrogen using gaseous hydrogenation method. Finally, hydride rim whose thickness is 0-95 μm at outer cladding surface was successively formed. On the other hand, ring compression tests which simulate pinch-type loading were conducted to investigate the mechanical property degradation depending on the hydride rim thickness. The results showed that as the thickness increases, the specimen ruptured earlier and fracture strain decreases. These results demonstrate that the hydride rim deteriorates the ductility of zirconium alloy cladding.

  16. Effect of porosity on the tensile properties of low ductility aluminum alloys

    Directory of Open Access Journals (Sweden)

    Gustavo Waldemar Mugica

    2004-06-01

    Full Text Available The literature contains reports of several studies correlating the porosity and mechanical properties of aluminum alloys. Most of these studies determine this correlation based on the parameter of global volumetric porosity. These reports, however, fail to separate the effects of microstructural features and porosity on alloys, though recognizing the influence of the latter on their mechanical properties. Thus, when the decrease in tensile strength due to the porosity effect is taken into account, the findings are highly contradictory. An analysis was made of the correlation between mechanical properties and global volumetric porosity and volumetric porosity in the fracture, as well as of the beta-Al5FeSi phase present in 380 aluminum alloy. Our findings indicate that mechanical properties in tension relating to global volumetric porosity lead to overestimations of the porosity effect in detriment to the mechanical properties. Moreover, the proposed models that take into account the effects of particles, both Si and beta-Al5FeSi, are unapplicable to low ductility alloys.

  17. Brittle-ductile transition for nuclear applications in contact with mercury

    International Nuclear Information System (INIS)

    Medina-Almazan, L.; Auger, T.; Gorse, D.

    2006-01-01

    In this work is studied the mercury embrittlement of austenitic stainless steel 316L and ferritic-martensitic steel T91 at ambient temperature in carrying out tensile tests on CCT (Center Cracked Tension) specimens at solicitation velocities between 1.67*10 -8 and 6.67*10 -3 m.s -1 . The results reveal that these two steels are sensitive to mercury embrittlement. A ductile-brittle transition of the steel 316L in contact to mercury in terms of the deformation velocity is observed. The early beginnings of such a transition are visible too on the steel T91 in the experiment conditions. On a some range of the solicitation velocity, the presence of mercury modifies the plastic behaviour of the material in inhibiting the nucleation-growth of the cavities. For these two steels in contact with mercury, in the area of velocities for which a brittle rupture is observed, it appears that the fracture is produced by de-cohesion of shear bands. (O.M.)

  18. Failure Mechanisms and Damage Model of Ductile Cast Iron Under Low-Cycle Fatigue Conditions

    Science.gov (United States)

    Wu, Xijia; Quan, Guangchun; MacNeil, Ryan; Zhang, Zhong; Sloss, Clayton

    2014-10-01

    Strain-controlled low-cycle fatigue (LCF) tests were conducted on ductile cast iron (DCI) at strain rates of 0.02, 0.002, and 0.0002/s in the temperature range from room temperature to 1073 K (800 °C). A constitutive-damage model was developed within the integrated creep-fatigue theory (ICFT) framework on the premise of strain decomposition into rate-independent plasticity and time-dependent creep. Four major damage mechanisms: (i) plasticity-induced fatigue, (ii) intergranular embrittlement (IE), (iii) creep, and (iv) oxidation were considered in a nonlinear creep-fatigue interaction model which represents the overall damage accumulation process consisting of oxidation-assisted fatigue crack nucleation and propagation in coalescence with internally distributed damage ( e.g., IE and creep), leading to final fracture. The model was found to agree with the experimental observations of the complex DCI-LCF phenomena, for which the linear damage summation rule would fail.

  19. Evaluation of Floor Response Spectrum considering Ductility of Structure

    Energy Technology Data Exchange (ETDEWEB)

    Park, Junhee; Choi, In-Kil [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    The FRS (floor response spectrum) is directly influenced by the behavior of structure under the seismic load. If the structure is nonlinear range, the energy dissipation will be occurred by the damage of structure and the maximum force will be reduced. In Zion method, the inelastic energy abortion factor has been used to consider the nonlinearity of structure. This factor was used for the seismic fragility of structure. For the seismic fragility of equipment, the uncertainty of this factor was used differently according to the story level. But this method is not warranted under the strong earthquake leads to the structural damage. Therefore it is needed to evaluate the FRS considering the nonlinear behavior of structure and to assessment the conservatism related to nonlinear behavior of structure in FRS. In this study, the nonlinear analysis was performed for the conservatism of FRS under the damage of structure. The conservatism of FRS by the nonlinear analysis was compared by that proposed by the Zion method. The conservatism of floor acceleration response for the equipment was evaluated by performing the nonlinear analysis. From the nonlinear analysis results, it was showed that the median and β{sub c} of FRSR was increased with the ductility of structure and the response of equipment had the resonance effect between the frequency of equipment and structure. The seismic capacity of equipment by the Zion method can be different from the real seismic capacity of equipment because the inelastic structure response factor has nothing to do with the ductility of structure. Therefore the median and COV for FRSR should be defined considering the ductility of structure and the frequency of equipment for more exactly evaluating the seismic capacity of equipment.

  20. The bainite reaction kinetics in austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Taran, Yu.N.; Uzlov, K.I.; Kutsov, A.Yu. [State Metall. Acad., Dnepropetrovsk (Ukraine). Phys. Metall. Dept.

    1997-11-01

    Bainitic reaction kinetics in ductile iron contained according to Ukrainian standard (weight%) 3.60-3.80 carbon, 2.60-2.80 Si, {proportional_to}0.12 Mn, {proportional_to}0.60 Cu and additionally alloyed by Mo (0.15-0.20) has been studied. It was found that the overall transformation kinetics becomes slower as transformation temperature increase. This is because more intensive redistribution of carbon into austenite at higher temperatures. Two austenites with different carbon content have been fixed and kinetics of their lattices parameters has been studied. (orig.). 6 refs.

  1. Manufacture of Toothed Elements in Nanoausferritic Ductile Iron

    Directory of Open Access Journals (Sweden)

    Myszka D.

    2014-10-01

    Full Text Available The technology currently used for the fabrication of toothed wheels, gear couplings and chain drums involves the induction hardening process or hardening and tempering after carburising. All these processes take a long time and cause adverse changes in the dimensions and surface quality of products, requiring post-treatment machining to remove the resulting cavities. The paper proposes the implementation of gear elements made of ductile iron with nanoausferritic matrix obtained by a new appropriate heat treatment process. The new material offers good performance characteristics and nearly no need for the application of other technological processes commonly used in the manufacture of gears.

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

    Science.gov (United States)

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

    2016-09-01

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

  3. Ductility and Ultimate Capacity of Prestressed Steel Reinforced Concrete Beams

    Directory of Open Access Journals (Sweden)

    Chengquan Wang

    2017-01-01

    Full Text Available Nonlinear numerical analysis of the structural behaviour of prestressed steel reinforced concrete (PSRC beams was carried out by using finite element analysis software ABAQUS. By comparing the load-deformation curves, the rationality and reliability of the finite element model have been confirmed; moreover, the changes of the beam stiffness and stress in the forcing process and the ultimate bearing capacity of the beam were analyzed. Based on the model, the effect of prestressed force, and H-steel to the stiffness, the ultimate bearing capacity and ductility of beam were also analyzed.

  4. Some problems in the production of ductile irons by investment casting

    Directory of Open Access Journals (Sweden)

    Yu Bo

    2008-02-01

    Full Text Available Because of the excellent performance of ductile irons and the unique superiority of investment casting, the preparation of complicated and thin-wall ductile iron castings by investment casting shows a good development prospect. In this present work, combined with the actual product experiments, the characteristics of shell making, spheroidization, inoculation and defect prevention are presented, and some suggestions are given for investment casting of ductile iron.

  5. Decommissioning and dismantling of nuclear facilities: Establishing methods for testing the safe design of ductile cast iron casks with higher content of metallic recycling material (EBER)

    International Nuclear Information System (INIS)

    Zenker, U.; Voelzke, H.; Droste, B.

    2001-01-01

    The safe design of ductile cast iron (DCI) casks with higher content of metallic recycling material is investigated. Based upon the requirements of transport and storage containers for radioactive waste appropriate test scenarios are defined. A representative accident scenario (5 m drop of a cubic DCI container with given material properties onto a hard repository ground simulating concrete target) is analysed numerically by means of the finite element method using three-dimensional models. Dynamic flow curves of ductile cast iron with different scrap metal additions which are necessary for precise elastic-plastic calculations are given. The accuracy and numerical stability of the resulting dynamic stresses and strains are investigated. A comparison between calculation results and measurements from drop tests with DCI containers shows, that known mechanical effects like bending vibrations of the container walls are reflected by the finite element models. The detailed stress analysis and knowledge of the material properties are prerequisites for the safety assessment concept developed for DCI casks with higher content of metallic recycling material. Equations for semi-elliptical surface cracks in the walls of a cubically shaped container which are used in the safety assessment concept are verified under dynamic conditions. This allows the specification of the maximum permissible size of crack-like flaws depending on the material quality. Mainly the fracture mechanical properties of ductile cast iron with higher content of metallic recycling material determine the suitability of such materials for transport and storage containers. (orig.) [de

  6. Fracture toughness of a welded super duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Pilhagen, Johan, E-mail: pilhagen@kth.se [Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden); Sieurin, Henrik [Scania CV AB, Södertälje (Sweden); Sandström, Rolf [Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden)

    2014-06-01

    Fracture toughness testing was conducted on standard single-edge notched bend bar specimens of base and weld metal. The material was the SAF 2906 super duplex stainless steel. The aim was to evaluate the susceptibility for brittle failure at sub-zero temperatures for the base and weld metal. The base metal was tested between −103 and −60 °C and was evaluated according to the crack-tip opening displacement method. The fracture event at and below −80 °C can be described as ductile until critical cleavage initiation occurs, which caused unstable failure of the specimen. The welding method used was submerged arc welding with a 7 wt% nickel filler metal. The welded specimens were post-weld heat treated (PWHT) at 1100 °C for 20 min and then quenched. Energy-dispersive X-ray spectroscopy analysis showed that during PWHT substitutional element partitioning occurred which resulted in decreased nickel content in the ferrite. The PWHT weld metal specimens were tested at −72 °C. The fracture sequence was critical cleavage fracture initiation after minor crack-tip blunting and ductile fracture.

  7. Fracture mechanics

    CERN Document Server

    Perez, Nestor

    2017-01-01

    The second edition of this textbook includes a refined presentation of concepts in each chapter, additional examples; new problems and sections, such as conformal mapping and mechanical behavior of wood; while retaining all the features of the original book. The material included in this book is based upon the development of analytical and numerical procedures pertinent to particular fields of linear elastic fracture mechanics (LEFM) and plastic fracture mechanics (PFM), including mixed-mode-loading interaction. The mathematical approach undertaken herein is coupled with a brief review of several fracture theories available in cited references, along with many color images and figures. Dynamic fracture mechanics is included through the field of fatigue and Charpy impact testing. Explains computational and engineering approaches for solving crack-related problems using straightforward mathematics that facilitate comprehension of the physical meaning of crack growth processes; Expands computational understandin...

  8. Supracondylar Fracture

    Directory of Open Access Journals (Sweden)

    Jessica Andrusaitis

    2017-07-01

    Full Text Available History of present illness: A 15-year-old male presented to the emergency department with right elbow pain after falling off a skateboard. The patient denied a decrease in strength or sensation but did endorse paresthesias to his hand. On exam, the patient had an obvious deformity of his right elbow with tenderness to palpation and decreased range of motion at the elbow. Sensation, motor function, and pulses were intact. Radiographic imaging was obtained. Significant findings: The pre-reduction films show a type III supracondylar fracture. There is complete displacement of the distal humerus anteriorly. Specific findings for supracondylar fracture include: a posterior fat pad (red arrow and a displaced anterior humeral line (yellow line.1 When no fracture is present, the anterior humeral line should intersect the middle third of the capitellum; in this X-ray, it does not intersect the capitellum at all. This X-ray demonstrates a normal radiocapitellar line (blue line that intersects the capitellum. The presence of a narrow anterior fat pad aka “sail sign” can be normal. Discussion: Supracondylar fractures of the humerus occur at the distal portion of the humerus without involving the growth plate.2 This is the second most common fracture in children overall. In children, it is the most common fracture of the elbow.3 This injury has a high risk of neurovascular compromise, such as compartment syndrome or ischemic contracture, and thus the clinician must perform immediate and frequent neurovascular assessments focusing on the distributions of the brachial artery in addition to the median, ulnar, and radial nerves.4 Hyperextension injuries that typically occur following a fall onto an outstretched arm are responsible for 95% of supracondylar fractures.1 A type I supracondylar fracture is non-displaced and can be treated with immobilization through a posterior splint and sling5 with close follow-up, type II is angulated but with an intact

  9. Development of a plastic fracture methodology. Final report

    International Nuclear Information System (INIS)

    Kanninen, M.F.; Hahn, G.T.; Broek, D.; Stonesifer, R.B.; Marschall, C.W.; Abou-Sayed, I.S.; Zahoor, A.

    1981-03-01

    A number of candidate fracture criteria were investigated to determine the basis for plastic fracture mechanics assessments of nuclear pressure vessels and other components exhibiting fully ductile behavior. The research was comprised of an integrated combination of stable crack growth experiments and elastic-plastic finite element analyses. The results demonstrated that many different fracture criteria can be used as the basis of a resistance curve approach to predicting stable crack growth and fracture instability. All have some disadvantages and none is completely unacceptable. On balance, the best criteria were found to be the J-integral for initiation and limited amounts of stable crack growth and the local crack tip opening angle for extended amounts of stable growth. A combination of the two, which may preserve the advantages of each while reducing their disadvantages, was also suggested by these results

  10. Mathematical Model of Bainitic Transformation in Austempered Ductile Iron

    Directory of Open Access Journals (Sweden)

    Olejarczyk-Wożeńska I.

    2017-12-01

    Full Text Available A mathematical model of austenite - bainite transformation in austempered ductile cast iron has been presented. The model is based on a model developed by Bhadeshia [1, 2] for modelling the bainitic transformation in high-silicon steels with inhibited carbide precipitation. A computer program has been developed that calculates the incubation time, the transformation time at a preset temperature, the TTT diagram and carbon content in unreacted austenite as a function of temperature. Additionally, the program has been provided with a module calculating the free energy of austenite and ferrite as well as the maximum driving force of transformation. Model validation was based on the experimental research and literature data. Experimental studies included the determination of austenite grain size, plotting the TTT diagram and analysis of the effect of heat treatment parameters on the microstructure of ductile iron. The obtained results show a relatively good compatibility between the theoretical calculations and experimental studies. Using the developed program it was possible to examine the effect of austenite grain size on the rate of transformation.

  11. Analysis of ductile crack growth by a simple damage model

    International Nuclear Information System (INIS)

    Zhang, Ch.; Gross, D.

    1993-01-01

    A strip damage-zone model of the Dugdale-Barenblatt-model type is presented in this paper for analyzing crack growth in ductile materials with damage evolution. In particular, a semi-infinite Mode-1 crack in plane stress or plane strain is considered. The damage is assumed to be present in form of dispersed microvoids, which are localized into a narrow strip direct ahead of a crack-tip. This configuration approximates the real situation naturally arising due to the high stress and strain concentrations in the proximity of the crack-tip. A simple damage model of the Gurson-model type is developed for uniaxial tension to describe the macroscopic properties of the strip damage-zone. Under small-scale yielding and small-scale damage conditions, a system of nonlinear integral equations for the plastic strain and the length of the damage-zone is derived. Numerical results are presented and discussed for the crack opening displacement, the stress and damage distribution within the plastic/damage zone, and the crack resistance curve. Special attention is devoted to reveal the effect of damage evolution on the ductile crack growth

  12. Mechanisms and mechanics of porosity formation in ductile iron castings

    Directory of Open Access Journals (Sweden)

    M. Perzyk

    2007-12-01

    Full Text Available Shrinkage defects in ductile iron castings can be of two basic types: shrinkage cavities associated with the liquid contraction prior to the expansion period of the iron as well as the porosity, which may appear even if the liquid shrinkage is fully compensated. In the present paper two possible mechanisms of the porosity are presented and analyzed. The first one is the Karsay’s mechanism based on the secondary shrinkage concept. The second one is the mechanism acting during the expansion period of the iron, first suggested by Ohnaka and co-authors and essentially modified by the present authors. The mechanical interactions between casting and mould are determined for the both mechanisms. Their analysis leads to the conclusion, that porosity forms during expansion period of the melt. The direct cause is the negative pressure which appears in the central part of the casting due to the differences in expansion coefficients of the fast cooling surface layer and slow cooling inner region. Observations concerning feeding behavior of ductile iron castings, based on this mechanism, agree well with industrial practice. The secondary shrinkage is not only needless to induce the porosity, but the corresponding mechanism of its occurrence, proposed by Karsay, does not seem to be valid.

  13. The effects of steel fibre reinforced concrete on system ductility

    Directory of Open Access Journals (Sweden)

    Yilmaz, U. S.

    2007-03-01

    Full Text Available Steel fibre-reinforced concrete is being used extensively today in both field applications and experimental studies on concrete strength and ductility. The state of passive confinement generated by the fibre delays cracking and enhances ductility. The present paper reports on both experimental and analytical studies. In the former, a series of 16 steel-fibre reinforced concrete prismatic specimens were subjected to axial loads and the respective axial load-unit strain diagrams were subsequently plotted to determine the effect of steel fibres on reinforced concrete column ductility. Secondly, an analytical study was run to determine the additional ductility accruing to a frame system when steel fibres are included in the concrete. Analytical models were generated for 16 two-storey, single-span reinforced concrete frames. The columns in these frames were designed to the same characteristics as the specimens used in the experimental tests. Non-linear static (pushover analyses were performed for each frame to obtain load-displacement curves and determine the effect of steel fibres on reinforced concrete column ductility.El hormigón reforzado con fibra de acero se emplea actualmente tanto en obra como en los trabajos experimentales para estudiar la resistencia mecánica y ductilidad del hormigón. El estado de confinamiento pasivo producido por la fibra retrasa la fisuración y aumenta la ductilidad. El presente trabajo es de índole tanto experimental como analítica. En primer lugar, en la parte experimental se aplica una fuerza axial a 16 probetas prismáticas (160 x 160 x 840 mm de hormigón reforzado con fibra de acero para determinar su comportamiento, obteniéndose las curvas de fuerza axial-deformación unitaria correspondientes a partir de los resultados observados. A partir de una evaluación de dichos resultados experimentales, se determina el efecto que ejercen las fibras de acero sobre la ductilidad de las probetas de hormigón armado

  14. Cyclic Ductile-Brittle Deformation during Temperature Decrease in Quartz-Rich Mylonites: Insights from the Calamita Schists (Elba Island, Italy)

    Science.gov (United States)

    Papeschi, S.; Menegon, L. M.; Musumeci, G.

    2017-12-01

    The Calamita Schists are a metamorphic complex that experienced transient (marked by mylonitic fabric overprinted by non-Andersonian brittle faults. In order to investigate the switch in deformation mechanism during temperature decrease at constant pressure (Pmarked by synkinematic biotite + cordierite + andalusite + K-feldspar assemblage, which is progressively replaced by retrograde white mica + chlorite. Quartz microfabric is defined by coarse-grained (100-900 µm) quartz porphyroclasts wrapped by ribbons of dynamically recrystallized finer grains ( 50 µm) showing a strong CPO. This fabric is cross cut by conjugate and synthetic C'-shear bands localized in porphyroclasts and marked by recrystallized fine grains (5-50 µm). EBSD data indicate that prism was the dominant slip system during crystal plastic deformation and dynamic recrystallization in the polycrystalline ribbons. Subsequently, brittle deformation localized along intracrystalline bands (both in conjugate sets and parallel to C' shear bands) within quartz porphyroclasts. The bands evolved in localized cataclastic micro-shear zones and in shear fractures, which localized fluid infiltration and healing by solution precipitation. The quartz new grains filling the bands are preferentially oriented with their c-axis parallel to the shear band boundary. This work highlights that deformation in the Calamita Schists switched over time from high-temperature dynamic recrystallization, accommodated by prism slip to low grade brittle-ductile processes. At the brittle-ductile transition strain partitioning was controlled by grain size and fluid penetration and was characterized by cyclical ductile-brittle mechanisms. In particular brittle failure localized in coarse-grains acted as the precursor for ductile C' shear bands.

  15. Analysis of steady-state ductile crack growth

    DEFF Research Database (Denmark)

    Niordson, Christian

    1999-01-01

    The fracture strength under quasi-static steady-state crack growth in an elastic-plastic material joined by a laser weld is analyzed. Laser welding gives high mismatch between the yield stress within the weld and the yield stress in the base material. This is due to the fast termic cycle, which...... the finite element mesh remains fixed relative to the tip of the growing crack. Fracture is modelled using two different local crack growth criteria. One is a crack opening displacement criterion, while the other is a model in which a cohesive zone is imposed in front of the crack tip along the fracture zone....... Both models predict that in general a thinner laser weld gives higher interface strength. Furthermore, both fracture criteria show, that the preferred path of the crack is close outside the weld material; a phenomenon also observed in experiments....

  16. Fundamental flow and fracture studies of HT-9

    International Nuclear Information System (INIS)

    Odette, G.R.; Lucas, G.E.; Maiti, R.; Sheckherd, J.W.

    1984-01-01

    Results of electron microscopy studies of cleavage crack formation and propagation in HT-9 are consistent with a model for stress-controlled cleavage in which the critical stress sigma/sub f//sup */ is related to the lath packet size. Moreover, sigma/sub f//sup */ appears to undergo a sharp transition at low temperatures and high strain rates; this is probably a result of a change in mechanism from slip- to twinning-nucleated cleavage. This change in sigma/sub f//sup */ effects corresponding changes in lower shelf fracture toughness. A simple two-parameter approach is shown to be a reasonable basis for predicting fracture loads for various size and crack-geometry bend specimens. These results indicated that cleavage fracture will occur near plastic collapse loads for thin wall structures containing shallow surface cracks. Results of an initial study of ductility in the cleavage regime indicate deflectional displacements on the order of 1-2 cm/m will be the limit for such shallow surface cracks in thin walls. The effects of dissolved hydrogen and stress state variations induced by side grooving were investigated. Hydrogen charges resulted in an average reduction in measured K/sub O/ values of about 17% and 5% in the ratio of maximum load fracture-to-collapse stress ratios. No significant effect of hydrogen on ductility was observed. Side grooving resulted in increases in both apparent K/sub O/ toughness levels and fracture-to-collapse stress ratios. Side grooving decreased ductility for shallow cracks and increased it for deep cracks. In general these effects are judged to be relatively modest compared to uncertainties in the measurements and the effects of significant variations in size and strength levels

  17. 35. Conference of the DVM Working Group on Fracture Processes: Advances in fracture and damage mechanics - simulation methods of fracture mechanics

    International Nuclear Information System (INIS)

    2003-01-01

    Subjects of the meeting were: Simulation of fatigue crack growth in real strucures using FEA (M. Fulland, Paderborn); Modelling of ductile crack growth (W. Brocks, Geesthacht); Advances in non-local modelling of ductile damage (F. Reusch et al., Berlin, Dortmund); Fracture mechanics of ceramics (D. Munz, Karlsruhe); From materials testing to vehicle crash testing (J.G. Blauel, Freiburg); Analytical simulation of crack growth in thin-walled structures (U. Zerbst, Geesthacht); The influence of intrinsic stresses on fatigue crack growth (C. Dalle Donne etc., Cologne, Dortmund, Pisa, and M. Sander, Paderborn); Fracture mechanical strength calculation in case of mixed mode loads on cracks (H.A. Richard, Paderborn); Numeric simulation of intrinsic stresses during welding (C. Veneziano, Freiburg); New research fields of the Fraunhofer-Institut fuer Werkstoffmechanik (P. Gumbsch, Head of the Institute, Freiburg); Modern developments and advances in fracture and damage mechanics; Numeric and experimental simulation of crack propagation and damage processes; Exemplary damage cases; Fracture mechanics in product development; Failure characteristics of lightweight constructional materials and joints [de

  18. Post-cracking Behaviour and Fracture Energy of Synthetic Fibre Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Marta KOSIOR-KAZBERUK

    2016-11-01

    Full Text Available The paper reports the results of experimental programme focused on the effect of various synthetic fibres on fracture properties and ductility of concrete. The fracture energy was assessed on beams with initial notches in three-point bend test. The incorporation of synthetic fibres had a slight effect on mechanical properties of concrete but, at the same time, it had a significant influence on the fracture energy by modification of post-cracking behaviour of concrete. It was found that the modern synthetic fibres might be able to impart significant toughness and ductility to concrete. However, the beneficial effect of fibres depends on their length and flexibility. The analysis of load-deflection curves obtained made it possible to fit the simple function, describing the post-peak behaviour of fibre reinforced concrete, which can be useful for the calculation of GF value.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.13246

  19. Development of re-crystallized W-1.1%TiC with enhanced room-temperature ductility and radiation performance

    International Nuclear Information System (INIS)

    Kurishita, H.; Matsuo, S.; Arakawa, H.; Sakamoto, T.; Kobayashi, S.; Nakai, K.; Takida, T.; Kato, M.; Kawai, M.; Yoshida, N.

    2010-01-01

    Ultra-fine grained (UFG) W-TiC compacts fabricated by powder metallurgical methods utilizing mechanical alloying (MA) are very promising for use in irradiation environments. However, the assurance of room-temperature ductility and enhancement in surface resistances to low-energy hydrogen irradiation are unsettled issues. As an approach to solution to these, microstructural modification by hot plastic working has been applied to UFG W-TiC processed by MA in a purified Ar or H 2 atmosphere and hot isostatic pressing (HIP). Hot plastically worked compacts have been subjected to 3-point bend tests at room temperature and TEM microstructural examinations. It is found that the microstructural modification allows us to convert UFG W-1.1%TiC to compacts exhibiting a very high fracture strength and appreciable ductility at room temperature. The compacts of W-1.1%TiC/Ar (MA atmosphere: Ar) and W-1.1%TiC/H 2 (MA atmosphere: H 2 ) exhibit re-crystallized structures with approximately 0.5 and 1.5 μm in grain size, respectively. It is shown that the enhancement of fracture resistance by microstructural modifications is attributed to significant strengthening of weak grain boundaries in the re-crystallized state. As a result the modified compacts exhibit superior surface resistance to low-energy deuteron irradiation.

  20. Combined macroscopic and microscopic approach to the fracture of metals. Technical progress report, July 1977--June 1978

    International Nuclear Information System (INIS)

    Gurland, J.; Rice, J.R.; Asaro, R.J.; Needleman, A.

    1978-06-01

    The work reported includes studies on: (1) The role of particles and interfaces in the initiation of fracture, including fundamentals of brittle versus ductile response of interfaces and observations on cavity growth by the cracking of grain or sub-grain boundaries adjacent to carbides in spheroidized steels; (2) Environment sensitive fracture mechanisms, particularly the effect of hydrogen in reducing tensile ductility by acceleration of the crack-like mode of cavity growth along grain boundaries in steels; (3) Models for elevated temperature diffusive processes of cavity growth on grain interfaces, including non-equilibrium effects and crack-like growth modes; (4) Localization of plastic deformation and the inception of ductile rupture; and (5) Elastic-plastic stress analysis, by finite elements, of growing cracks and examination of criteria for stable crack growth

  1. Physics-based Inverse Problem to Deduce Marine Atmospheric Boundary Layer Parameters

    Science.gov (United States)

    2017-03-07

    please find the Final Technical Report with SF 298 for Dr. Erin E. Hackett’s ONR grant entitled Physics -based Inverse Problem to Deduce Marine...From- To) 07/03/2017 Final Technica l Dec 2012- Dec 2016 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Physics -based Inverse Problem to Deduce Marine...19b. TELEPHONE NUMBER (Include area code) 843-349-4087 Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 Physics -Based Inverse Problem To

  2. Investigation of Mechanical Properties and Fracture Simulation of Solution-Treated AA 5754

    Science.gov (United States)

    Kumar, Pankaj; Singh, Akhilendra

    2017-10-01

    In this work, mechanical properties and fracture toughness of as-received and solution-treated aluminum alloy 5754 (AA 5754) are experimentally evaluated. Solution heat treatment of the alloy is performed at 530 °C for 2 h, and then, quenching is done in water. Yield strength, ultimate tensile strength, impact toughness, hardness, fatigue life, brittle fracture toughness (K_{Ic} ) and ductile fracture toughness (J_{Ic} ) are evaluated for as-received and solution-treated alloy. Extended finite element method has been used for the simulation of tensile and fracture behavior of material. Heaviside function and asymptotic crack tip enrichment functions are used for modelling of the crack in the geometry. Ramberg-Osgood material model coupled with fracture energy is used to simulate the crack propagation. Fracture surfaces obtained from various mechanical tests are characterized by scanning electron microscopy.

  3. Galeazzi fracture.

    Science.gov (United States)

    Atesok, Kivanc I; Jupiter, Jesse B; Weiss, Arnold-Peter C

    2011-10-01

    Galeazzi fracture is a fracture of the radial diaphysis with disruption at the distal radioulnar joint (DRUJ). Typically, the mechanism of injury is forceful axial loading and torsion of the forearm. Diagnosis is established on radiographic evaluation. Underdiagnosis is common because disruption of the ligamentous restraints of the DRUJ may be overlooked. Nonsurgical management with anatomic reduction and immobilization in a long-arm cast has been successful in children. In adults, nonsurgical treatment typically fails because of deforming forces acting on the distal radius and DRUJ. Open reduction and internal fixation is the preferred surgical option. Anatomic reduction and rigid fixation should be followed by intraoperative assessment of the DRUJ. Further intraoperative interventions are based on the reducibility and postreduction stability of the DRUJ. Misdiagnosis or inadequate management of Galeazzi fracture may result in disabling complications, such as DRUJ instability, malunion, limited forearm range of motion, chronic wrist pain, and osteoarthritis.

  4. Fracture controlled feldspar shape fabrics in deformed quartzo-feldspathic rocks

    Science.gov (United States)

    Andrews, J. R.

    The behaviour of feldspar in the brittle-ductile transition region has often been discussed in models dominated by mechanisms of extension fracturing. In this example, a small Caledonian granitic pluton from NW Ireland, feldspar shape changes are primarily accomplished by small displacements upon numerous shear fractures. These fractures developed as Riedel and anti-Riedel shears as the granite was synkinematically deformed in a regional shear zone. The deformation took place under greenschist facies conditions at strain rates estimated between 10 -13 and 10 -14 s -1.

  5. The ductile/brittle transition provides the critical test for materials failure theory

    Science.gov (United States)

    Christensen, Richard M.

    2018-02-01

    It is reasoned that any materials failure theory that claims generality must give full account of ductile versus brittle failure behaviour. Any such proposed theory especially must admit the capability to generate the ductile/brittle transition. A derivation of the failure surface orientations from a particular isotropic materials failure theory reveals that uniaxial tension has its ductile/brittle transition at T/C = 1/2, where T and C are the uniaxial strengths. Between this information and the corresponding ductile/brittle transition in uniaxial compression it becomes possible to derive the functional form for the fully three-dimensional ductile/brittle transition. These same general steps of verification must be fulfilled for any other candidate general failure theory.

  6. Comparative study of TIG and SMAW root welding passes on ductile iron cast weldability

    Directory of Open Access Journals (Sweden)

    J. Cárcel-Carrasco

    2017-01-01

    Full Text Available This work compares the weldability of ductile iron when: (I a root weld is applied with a tungsten inert gas (TIG process using an Inconel 625 source rod and filler welds are subsequently applied using coated electrodes with 97,6%Ni; and (II welds on ductile iron exclusively made using the manual shielded metal arc welding technique (SMAW. Both types of welds are performed on ductile iron specimen test plates that are subjected to preheat and post-weld annealing treatments. Samples with TIG root-welding pass shown higher hardness but slightly lower ductility and strength. Both types of welding achieved better ductile and strength properties than ones found in literature.

  7. Development of Flexible Link Slabs using Ductile Fiber Reinforced Concrete

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi

    Civil engineering structures with large dimensions, such as multi-span bridges, overpasses and viaducts, are typically equipped with mechanical expansion joints. These joints allow the individual spans of the structure to undergo unrestrained deformations due to thermal expansions and load......, it is suggested to replace the mechanical expansion joint and implement a flexible, precast ductile concrete link slab element between simply supported bridge spans. To design and analyze the suggested link slab element, each constituent of the element, i.e. the structural reinforcement and the cementitious...... and under cyclic loading. The findings from the investigations on bond-slip, tension stiffening and tension strengthening are used in Chapter 5 as inputfor the design and analysis of the loaddeformation response and the crack development of a prefabricated flexible link slab elements potentially connecting...

  8. Tensile properties of austempered ductile iron under thermomechanical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Achary, J.

    2000-02-01

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

  9. Dry sliding wear of Ni alloyed austempered ductile iron

    Directory of Open Access Journals (Sweden)

    E. Akbarzadeh Chiniforush

    2016-09-01

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

  10. Modelling of damage development and ductile failure in welded joints

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau

    This thesis focuses on numerical analysis of damage development and ductile failure in welded joints. Two types of welds are investigated here. First, a study of the localization of plastic flow and failure in aluminum sheets, welded by the relatively new Friction Stir (FS) Welding method, has been...... conducted ([P1], [P2], [P7]-[P9]). The focus in the thesis is on FS-welded 2xxx and 6xxx series of aluminum alloys, which are attractive, for example, to the aerospace industry, since the 2024 aluminum in particular, is typically classified as un-weldable by conventional fusion welding techniques. Secondly......, a study of the damage development in Resistance SpotWelded joints, when subject to the commonly used static shear-lab or cross-tension testing techniques, has been carried out ([P3]-[P6]). The focus in thesis is on the Advanced High Strength Steels, Dual-Phase 600, which is used in for example...

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

    Science.gov (United States)

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

    2017-01-01

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

  12. Appreciation of Triaxiality Influence in Plastic Deformation Accompanying Ductile Rupture

    Science.gov (United States)

    Coseru, Ancuta-Ioana; Zichil, Valentin; Lupascu, Stefan

    2017-12-01

    In this paper, the authors propose a studying method for the deformation that appears before crack of ductile materials using the Lode parameter determined by the numerical calculation applied on simple models, verified in previous studies. In order to highlight the influence of the Lode parameter, the tests were performed at simple but also at compound tests. The necessity of these studies lies in the fact that the acknowledged models (the use of the integral J, the critical stress intensity factor Kc or the CPCD method) do not fully explain the phenomenon of deformation before breaking the elasto-plastic materials. The tests were imagined under the form of sets. Each set of tests was performed on smooth specimens and on specimens with a notch radius of 0.5, 2, 4 and 10 mm. Also, each set of tests was performed for pure tensile and combined tensile-torque test.

  13. Trochanteric fractures

    International Nuclear Information System (INIS)

    Herrlin, K.; Stroemberg, T.; Lidgren, L.; Walloee, A.; Pettersson, H.; Lund Univ.

    1988-01-01

    Four hundred and thirty trochanteric factures operated upon with McLaughlin, Ender or Richard's osteosynthesis were divided into 6 different types based on their radiographic appearance before and immediately after reposition with special reference to the medial cortical support. A significant correlation was found between the fracture type and subsequent mechanical complications where types 1 and 2 gave less, and types 4 and 5 more complications. A comparison of the various osteosyntheses showed that Richard's had significantly fewer complications than either the Ender or McLaughlin types. For Richard's osteosynthesis alone no correlation to fracture type could be made because of the small number of complications in this group. (orig.)

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

    Directory of Open Access Journals (Sweden)

    D. Myszka

    2009-01-01

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

  15. Development of ductile high-strength chromium alloys, phase 2

    Science.gov (United States)

    Filippi, A. M.

    1973-01-01

    Strength and ductility were evaluated for chromium alloys dispersion hardened with the putative TaC, TaB, CbC, and CbB compounds. TaC and TaB proved to be the most potent strengtheners, but when combined, their effect far outweighed that produced individually. Tests at 1422 K (2100 F) on an alloy containing these two compounds at the combined level of 0.5 m/o revealed a 495 MN/sq m (70 ksi) tensile strength for wrought material, and a 100 hour rupture strength of 208 MN/sq m (30 ksi) when solution annealed and aged to maximize creep resistance. These levels of high temperature strength greatly exceed that reported for any other chromium-base alloy. The ductile-to-brittle transition temperature (DBTT) of the two phase strengthened alloy occurred at approximately 588 K (600 F) when heat treated to optimize creep strength and was not improved by fabrication to produce a wrought and recovered microstructure. The lowest DBTT measured on any of the alloys investigated was 422 K (300 F). Strengthening phases actually formed in Cr-Ta-B and Cr-Cb-B compositions are probable M2CrB2 (M=Ta or Cb) compounds of tetragonal crystal structure. The likely habit relationship between these compounds and chromium is postulated. Cube habit coherency was identified for TaC precipitation in chromium by electron microscopy. In another study, the maximum solubility of carbon in chromium was indicated to lie between 3/4 and 1 a/o and that of boron to be 1/2 a/o.

  16. Methodology of Fault Diagnosis in Ductile Iron Melting Process

    Directory of Open Access Journals (Sweden)

    Perzyk M.

    2016-12-01

    Full Text Available Statistical Process Control (SPC based on the Shewhart’s type control charts, is widely used in contemporary manufacturing industry, including many foundries. The main steps include process monitoring, detection the out-of-control signals, identification and removal of their causes. Finding the root causes of the process faults is often a difficult task and can be supported by various tools, including data-driven mathematical models. In the present paper a novel approach to statistical control of ductile iron melting process is proposed. It is aimed at development of methodologies suitable for effective finding the causes of the out-of-control signals in the process outputs, defined as ultimate tensile strength (Rm and elongation (A5, based mainly on chemical composition of the alloy. The methodologies are tested and presented using several real foundry data sets. First, correlations between standard abnormal output patterns (i.e. out-of-control signals and corresponding inputs patterns are found, basing on the detection of similar patterns and similar shapes of the run charts of the chemical elements contents. It was found that in a significant number of cases there was no clear indication of the correlation, which can be attributed either to the complex, simultaneous action of several chemical elements or to the causes related to other process variables, including melting, inoculation, spheroidization and pouring parameters as well as the human errors. A conception of the methodology based on simulation of the process using advanced input - output regression modelling is presented. The preliminary tests have showed that it can be a useful tool in the process control and is worth further development. The results obtained in the present study may not only be applied to the ductile iron process but they can be also utilized in statistical quality control of a wide range of different discrete processes.

  17. The Silumin Coat Structure on Alloy Ductile Iron

    Directory of Open Access Journals (Sweden)

    Szymczak T.

    2013-03-01

    Full Text Available The work presents the research results of the silumin coat structure applied on the carbidic alloy ductile iron with the metal matrix: pearlitic, bainitic and martensitic. The coats were made in the AlSi5 silumin bath at the temperature tk = 750±5°C. The holding time of cast iron element in the bath was τ = 180s. Irrespective of the kind of tested ductile iron the obtained coat consisted of three layers with a different phase composition. The first layer from the cast iron ground “g1`” is built from Fe4CSi carbide which contains selected alloy additives of the cast iron. On it the second layer “g1``” crystallizes. It consists of the AlFeSi inter-metallic phase which can appear in its pure form or contain a small quantity of the alloy additives of the cast iron. The last external part of the layer “g2” mainly consists of the hypo-eutectic phases of silumin. The AlFeSi inter-metallic phases in the form of free precipitations with a lamellar or faceted morphology can also appear there. These phases also can contain a small quantity of the alloy additives of the cast iron. More than that, in all the layers of the coat there are graphite precipitations. The phenomenon of graphite movement to the coat is caused by intensive dissolving of the cast iron element surface by the aluminum of the silumin bath.

  18. Neoarchean ductile deformation in the Northeastern North China Craton: The Shuangshanzi ductile shear zone in Qinglong area, eastern Heibei, China

    Science.gov (United States)

    Liu, Boran; Neubauer, Franz; Liu, Junlai; Jin, Wei; Li, Weimin; Liang, Chenyue

    2017-04-01

    Archean granitic gneiss domes and greenstone belts are well-preserved in eastern NCC, one of the oldest Archean terrains in the world. The Shuangshanzi ductile shear zone in Qinglong, eastern Hebei Province is located between an Archean granitic gneiss dome and a greenstone belt within an uplift in eastern NCC. Supracrustal rocks from the Neoarchean Shuangshanzi and Zhuzhangzi Groups were sheared, but some Archean granitic gneisses were also involved in the shearing along the eastern margin. In the southern part, the narrow NE-trending shear zone dips NW with dip angles of 40-60° and, in the northern part, the shear zone dips NWN with dip angles of 70-85°. Microstructural and EBSD fabric analyses suggest that the shear zone was developed at upper greenschist facies to lower amphibolite facies conditions with deformation temperatures of 400 to 550°C.LA-ICP-MS zircon U-Pb ages of mylonitized granitic rocks and undeformed quartz diorite cutting the shear zone suggest that the Shuangshanzi ductile shear zone was formed between 2550 Ma and 2452 Ma. Detailed kinematic studies of the shear zone show a clear sinistral shear sense with a slightly oblique-slip component in the northern part and a sinistral transtensional slip component in the southern part. It is therefore suggested that the shear zone was formed during the Anziling doming with respect to the down-slipping Neoarchean Shuangshanzi and Zhuzhangzi Groups. The difference in kinematics along the southern and the northern sections is interpreted to be caused by the doming with an uneven clockwise spiral rotation. The BIF-rich supracrustal rocks have higher density than their neighboring granitic gneisses, and therefore can easily sink to form synclines by sagduction processes. The sagduction is mainly triggered by gravitational inversion of high density supracrustal rocks with respect to relatively light granitic gneisses within the dome. As a result, the gneisses synchronously moved upward. A shear zone was

  19. CONSISTENT USE OF THE KALMAN FILTER IN CHEMICAL TRANSPORT MODELS (CTMS) FOR DEDUCING EMISSIONS

    Science.gov (United States)

    Past research has shown that emissions can be deduced using observed concentrations of a chemical, a Chemical Transport Model (CTM), and the Kalman filter in an inverse modeling application. An expression was derived for the relationship between the "observable" (i.e., the con...

  20. Complete amino acid sequence of human intestinal aminopeptidase N as deduced from cloned cDNA

    DEFF Research Database (Denmark)

    Cowell, G M; Kønigshøfer, E; Danielsen, E M

    1988-01-01

    The complete primary structure (967 amino acids) of an intestinal human aminopeptidase N (EC 3.4.11.2) was deduced from the sequence of a cDNA clone. Aminopeptidase N is anchored to the microvillar membrane via an uncleaved signal for membrane insertion. A domain constituting amino acid 250...

  1. Techniques developed to evaluate the fracture toughness offast breeder reactor duct. [Use of J-integral tests

    Energy Technology Data Exchange (ETDEWEB)

    Huang, F. H.; Wire, G. L.

    1979-01-01

    Large changes in strength and ductility of metals after irradiation are known to occur. The fracture toughness of irradiated metals, which is related to the combined strength and ductility of a material, may be significantly reduced and the potential for unstable crack extension increased. Therefore, the resistance of cladding and duct materials to fracture after exposure to fast neutron environments is of concern. Existing Type 316 stainless steel irradiated ducts are relatively thin and since this material retains substantial ductility, even after irradiation, the fracture behavior of the duct material cannot be analyzed by linear elastic fracture mechanics techniques. Instead, the multispecimen R-curve method and J-integral analysis were used to develop an experimental approach to evaluate the fracture toughness of thin breeder reactor duct materials irradiated at elevated temperatures. Alloy A-286 was chosen for these experiments because the alloy exhibits elastic/plastic behavior and the fracture toughness data of thicker (12 mm) specimens were available for comparison. Technical problems associated with specimen buckling and remote handling were treated in this work. The results are discussed in terms of thickness criterion for plane strain.

  2. Element migration of pyrites during ductile deformation of the Yuleken porphyry Cu deposit (NW-China)

    Science.gov (United States)

    Hong, Tao; Xu, Xing-Wang; Gao, Jun; Peters, Stephen; Li, Jilei; Cao, Mingjian; Xiang, Peng; Wu, Chu; You, Jun

    2017-01-01

    The strongly deformed Yuleken porphyry Cu deposit (YPCD) occurs in the Kalaxiangar porphyry Cu belt (KPCB), which occupies the central area of the Central Asian Orogenic Belt (CAOB) between the Sawu’er island arc and the Altay Terrane in northern Xinjiang. The YPCD is one of several typical subduction-related deposits in the KPCB, which has undergone syn-collisional and post-collisional metallogenic overprinting. The YPCD is characterized by three pyrite-forming stages, namely a hydrothermal stage A (Py I), a syn-ductile deformation stage B (Py II) characterized by Cu-Au enrichment, and a fracture-filling stage C (Py III). In this study, we conducted systematic petrographic and geochemical studies of pyrites and coexist biotite, which formed during different stages, in order to constrain the physicochemical conditions of the ore formation. Euhedral, fragmented Py I has low Pb and high Te and Se concentration and Ni contents are low with Co/Ni ratios mostly between 1 and 10 (average 9.00). Py I is further characterized by enrichments of Bi, As, Ni, Cu, Te and Se in the core relative to the rim domains. Anhedral round Py II has moderate Co and Ni contents with high Co/Ni ratios >10 (average 95.2), and average contents of 46.5 ppm Pb and 5.80 ppm Te. Py II is further characterized by decreasing Bi, Cu, Pb, Zn, Ag, Te, Mo, Sb and Au contents from the rim to the core domains. Annealed Py III has the lowest Co content of all pyrite types with Co/Ni ratios mostly element migration behavior during the different stages of deformation and, thus, mineralisation.

  3. Extensional ductile tectonics of the Sioule metamorphic series (Variscan French Massif Central)

    Science.gov (United States)

    Faure, M.; Grolier, J.; Pons, J.

    1993-09-01

    In the Northern part of the Variscan French Massif Central, the Sioule series, from top to bottom, consists of a pre-Viséan granite, migmatite, gneiss and mica schist. Two ductile deformations have been recognized. The earlier phase is characterized by a north-east-south-west trending stretching lineation; the second phase, characterized by a north-west-south-east trending mineral, stretching and crenulation lineation, is better marked in the lower mica schist part than in the upper granito-gneissic part. This second phase occurred during retrogression of the metamorphic rocks; related shear criteria indicate a top to the south-west shear. The Namurian-Westphalian magmatic bodies such as the Echassières leucogranite, Pouzol-Servant microgranite and numerous north-east -south-west trending microgranite dykes are emplaced in extensional fractures related to the same north-west-south-east maximum stretching direction. The asymmetrical shapes of the two granitic massifs indicate that they intruded towards the south-east. The synkinematic retrogression of the metamorphic rocks, the shape of the magmatic bodies and a re-examination of the numerous available data support the interpretation that the deformation is due to the extensional tectonic regime related to the Variscan crustal re-quilibration. This interpretation is in agreement with the correlation of the Sioule series with the Chavanon series. The two series belong to a unique tectono-metamorphic unit left-laterally offset by the Stephanian motion of the Sillon Houiller fault. This study also shows that the Sillon Houiller did not play a significant part during the Namurian-Westphalian extensional tectonics of the Massif Central.

  4. Assessment of Ductile-to-Brittle Transition Behavior of Localized Microstructural Regions in a Friction-Stir Welded X80 Pipeline Steel with Miniaturized Charpy V-Notch Testing

    Science.gov (United States)

    Avila, Julian A.; Lucon, Enrico; Sowards, Jeffrey; Mei, Paulo Roberto; Ramirez, Antonio J.

    2016-06-01

    Friction-stir welding (FSW) is an alternative welding process for pipelines. This technology offers sound welds, good repeatability, and excellent mechanical properties. However, it is of paramount importance to determine the toughness of the welds at low temperatures in order to establish the limits of this technology. Ductile-to-brittle transition curves were generated in the present study by using a small-scale instrumented Charpy machine and miniaturized V-notch specimens (Kleinstprobe, KLST); notches were located in base metal, heat-affected, stirred, and hard zones within a FSW joint of API-5L X80 Pipeline Steel. Specimens were tested at temperatures between 77 K (-196 °C) and 298 K (25 °C). Based on the results obtained, the transition temperatures for the base material and heat-affected zone were below 173 K (-100 °C); conversely, for the stirred and hard zones, it was located around 213 K (-60 °C). Fracture surfaces were characterized and showed a ductile fracture mechanism at high impact energies and a mixture of ductile and brittle mechanisms at low impact energies.

  5. Hydroformability study of seamless tube using Gurson-Tvergaard-Needleman (GTN) fracture model

    Science.gov (United States)

    Harisankar, K. R.; Omar, A.; Narasimhan, K.

    2017-09-01

    Tube hydroforming process is an advanced manufacturing process in which tube acting as blank is placed in between the dies and deformed with the help of hydraulic pressure. It has several advantages over conventional stamping process such as high strength to weight ratio, higher reliability, less tooling cost etc. Fracture surface investigation of tube hydroformed samples reveal dimple formation in the form of void coalescence which is a characteristic feature of ductile fracture. Hence, in order to accurately predict the limiting strains at fracture it is important to model the process using ductile damage criteria. Fracture criteria are broadly classified into two, microscopic and macroscopic. In the present work Gurson-Tvergaard-Neeedleman (GTN) model, which is a microscopic based ductile damage criteria, was used for predicting the limiting strains at fracture for seamless steel tubes and implemented in explicit finite element software, ABAQUS, for variety of strain path and boundary conditions to obtain fracture based forming limit diagram. The original void porosity, the critical porosity and fracture porosity of the Gurson-Tvergaard-Needleman model were determined by image analysis of scanning electron micrographs of the specimen at different testing conditions of the uniaxial tensile test. The other parameters of the model were determined by using inverse approach combined with uniaxial tensile test and simulation. Predicted FLD is found to be in good agreement with the experimental FLD. Furthermore, numerical simulation based parametric study was carried out to understand the impact of various GTN parameters on different aspects of formability parameters such as bursting pressure, bulge height, principal strains and strain path to develop the understanding of deformation and fracture behaviour at the micro-level during tube hydroforming process.

  6. Optimization of Multi-Cluster Fracturing Model under the Action of Induced Stress in Horizontal Wells

    Directory of Open Access Journals (Sweden)

    Shanyong Liu

    2016-05-01

    Full Text Available Volume fracturing in shale gas forms complex fracture networks and increases stimulated reservoir volume through large-scale fracturing operation with plug-perforation technology. However, some perforation clusters are stimulated unevenly after fracturing. This study aims to solve this problem by analyzing the shortcomings of the conventional fracturing model and developing a coupled model based on the 2D fracture motion equation, energy conservation law, linear elastic mechanics, and stress superposition principle. First, a multi-fracture in-situ stress model was built by studying the induced stress produced by the fracture initiation to deduce the multi-fracture induced stress impact factor on the basis of the stress superposition principle. Then, the classical Perkins–Kern–Nordgren model was utilized with the crustal stress model. Finally, a precise fracturing design method was used to optimize perforation and fracturing parameters under the new model. Results demonstrate that the interference effect among fractures is the major factor causing the non-uniform propagation of each fracture. Compression on the main horizontal stress increases the net pressure. Therefore, both the degree of operation difficulty and the complexity of fracture geometry are improved. After applying the optimal design, the production is increased by 20%, and the cost is reduced by 15%.

  7. Challenges in the Japan Beyond-Brittle Project (JBBP) for EGS development beyond the brittle-ductile transition

    Science.gov (United States)

    Asanuma, H.; Muraoka, H.; Tsuchiya, N.; Ito, H.

    2013-12-01

    Development using Engineered Geothermal System (EGS) technologies is considered to be the best solution to the problems of the localized distribution of geothermal resources. However, it is considered that a number of problems, including low water recovery rate, difficulty in design of the reservoir, and induced earthquake, would appear in Japanese EGS. These problems in the development of EGS reservoirs cannot be readily solved in Japan because they are intrinsically related to the physical characteristics and tectonic setting of the brittle rock mass. Therefore, we have initiated the Japan Beyond-Brittle Project (JBBP), which will take a multidisciplinary scientific approach, including geology, geochemistry, geophysics, water-rock interactions, rock mechanics, seismology, drilling technology, well-logging technology, and reservoir engineering. The science and technology required for the creation and control of geothermal reservoirs in superheated rocks in the ductile zone is at the frontier of modern research in most of the related disciplines. Solutions to the associated problems will not easily be found without international collaboration among researchers and engineers. For this reason, in March, 2013 we held a five-day ICDP-supported workshop in Japan to review and discuss various scientific and technological issues related to the JBBP. Throughout the discussions at the workshop on characteristics of the beyond-brittle rock mass and creation and control of EGS reservoirs in the ductile zone, it has concluded that there are two end-member reservoir models that should be considered (Fig. 1). The JBBP reservoir type-1 would be created near the top of the brittle-ductile transition (BDT) and connected to pre-existing hydrothermal systems, which would increase productivity and provide sustainability. The JBBP reservoir type-2 would be hydraulically or thermally created beyond the BDT, where pre-existing fractures are less permeable, and would be hydraulically

  8. Analytical investigation of bidirectional ductile diaphragms in multi-span bridges

    Science.gov (United States)

    Wei, Xiaone; Bruneau, Michel

    2018-04-01

    In the AASHTO Guide Specifications for Seismic Bridge Design Provisions, ductile diaphragms are identified as Permissible Earthquake-Resisting Elements (EREs), designed to help resist seismic loads applied in the transverse direction of bridges. When adding longitudinal ductile diaphragms, a bidirectional ductile diaphragm system is created that can address seismic excitations acting along both the bridge's longitudinal and transverse axes. This paper investigates bidirectional ductile diaphragms with Buckling Restrained Braces (BRBs) in straight multi-span bridge with simply supported floating spans. The flexibility of the substructures in the transverse and longitudinal direction of the bridge is considered. Design procedures for the bidirectional ductile diaphragms are first proposed. An analytical model of the example bridge with bidirectional ductile diaphragms, designed based on the proposed methodology, is then built in SAP2000. Pushover and nonlinear time history analyses are performed on the bridge model, and corresponding results are presented. The effect of changing the longitudinal stiffness of the bidirectional ductile diaphragms in the end spans connecting to the abutment is also investigated, in order to better understand the impact on the bridge's dynamic performance.

  9. Ductility demands on buckling-restrained braced frames under earthquake loading

    Science.gov (United States)

    Fahnestock, Larry A.; Sause, Richard; Ricles, James M.; Lu, Le-Wu

    2003-12-01

    Accurate estimates of ductility demands on buckling-restrained braced frames (BRBFs) are crucial to performance-based design of BRBFs. An analytical study on the seismic behavior of BRBFs has been conducted at the ATLSS Center, Lehigh University to prepare for an upcoming experimental program. The analysis program DRAIN-2DX was used to model a one-bay, four-story prototype BRBF including material and geometric nonlinearities. The buckling-restrained brace (BRB) model incorporates both isotropic and kinematic hardening. Nonlinear static pushover and time-history analyses were performed on the prototype BRBF. Performance objectives for the BRBs were defined and used to evaluate the time-history analysis results. Particular emphasis was placed on global ductility demands and ductility demands on the BRBs. These demands were compared with anticipated ductility capacities. The analysis results, along with results from similar previous studies, are used to evaluate the BRBF design provisions that have been recommended for codification in the United States. The results show that BRB maximum ductility demands can be as high as 20 to 25. These demands significantly exceed those anticipated by the BRBF recommended provisions. Results from the static pushover and time-history analyses are used to demonstrate why the ductility demands exceed those anticipated by the recommended provisions. The BRB qualification testing protocol contained in the BRBF recommended provisions is shown to be inadequate because it requires only a maximum ductility demand of at most 7.5. Modifications to the testing protocol are recommended.

  10. On the fracture toughness of advanced materials

    Energy Technology Data Exchange (ETDEWEB)

    Launey, Maximilien E.; Ritchie, Robert O.

    2008-11-24

    Few engineering materials are limited by their strength; rather they are limited by their resistance to fracture or fracture toughness. It is not by accident that most critical structures, such as bridges, ships, nuclear pressure vessels and so forth, are manufactured from materials that are comparatively low in strength but high in toughness. Indeed, in many classes of materials, strength and toughness are almost mutually exclusive. In the first instance, such resistance to fracture is a function of bonding and crystal structure (or lack thereof), but can be developed through the design of appropriate nano/microstructures. However, the creation of tough microstructures in structural materials, i.e., metals, polymers, ceramics and their composites, is invariably a compromise between resistance to intrinsic damage mechanisms ahead of the tip of a crack (intrinsic toughening) and the formation of crack-tip shielding mechanisms which principally act behind the tip to reduce the effective 'crack-driving force' (extrinsic toughening). Intrinsic toughening is essentially an inherent property of a specific microstructure; it is the dominant form of toughening in ductile (e.g., metallic) materials. However, for most brittle (e.g., ceramic) solids, and this includes many biological materials, it is largely ineffective and toughening conversely must be developed extrinsically, by such shielding mechanisms as crack bridging. From a fracture mechanics perspective, this results in toughening in the form of rising resistance-curve behavior where the fracture resistance actually increases with crack extension. The implication of this is that in many biological and high-strength advanced materials, toughness is developed primarily during crack growth and not for crack initiation. This is an important realization yet is still rarely reflected in the way that toughness is measured, which is invariably involves the use of single-value (crack-initiation) parameters such as

  11. Fracture of Fe--Cr--Mn austenitic steel

    International Nuclear Information System (INIS)

    Caskey, G.R. Jr.

    1979-01-01

    Tensile tests of Tenelon (U.S. Steel), a nitrogen-strengthened iron-base alloy containing 18% chromium and 15% manganese, demonsterated that cleavage fracture can occur in some austenitic steels and is promoted by the presence of hydrogen. Tensile failure of Tenelon at 78 0 K occurred with no detectable necking at low strain levels. The fracture surface contained cleavage facets that lay along coherent twin boundaries oriented transversely to the tensile axis. Charging gaseous hydrogen at 679 MPa pressure and 650 0 K had no significant effect on the mechanical behavior or fracture mode at 78 0 K, but raised the ductile-to-brittle transition temperature from less than 200 0 K to about 250 0 K

  12. Effect of Fracture on Crushing of Ship Structures

    DEFF Research Database (Denmark)

    Simonsen, Bo Cerup; Abramowicz, W.

    2003-01-01

    and theories on the crushing response of typical strength elements. The theories are derived for an infinitely ductile material response and then consistently modified to include the effect of fracture. Theoretical formulas are compared with results of large-scale experiments performed at the Technical......This paper is concerned with loads and energy absorption during crushing of ship structures. Particular focus is on the effect of fracture of welds or parent material on the energy absorption of typical structural subassemblies of ships during deep collapse. The paper presents experiments...... absorption in axial crushing of typical ship structural components. This effect of fracture has been neglected in previously published studies of bow crushing mechanics....

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

    Directory of Open Access Journals (Sweden)

    M. Janjić

    2016-07-01

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

  14. Ductile shape memory alloys of the Cu-Al-Mn system

    International Nuclear Information System (INIS)

    Kainuma, R.; Takahashi, S.; Ishida, K.

    1995-01-01

    Cu-Al-Mn shape memory alloys with enhanced ductility have been developed by decreasing the degree of order in the β parent phase. Cu-Al-Mn alloys with Al contents lower than 18% exhibit good ductility with elongations of about 15% and excellent cold-workability arising from a lower degree of order in the Heusler (L21) β 1 parent phase, without any loss in their shape memory behavior. In this paper the mechanical and shape memory characteristics, such as the cold-workability, the Ms temperatures, the shape memory effect and the pseudo-elasticity of such ductile Cu-Al-Mn alloys are presented. (orig.)

  15. Hot ductility of structural steels melted with the use of direct reduction charge

    International Nuclear Information System (INIS)

    Marchenko, V.N.; Bulat, S.I.; Litvinenko, D.A.

    1982-01-01

    A possibility of the use of direct reduction charge during the open arc melting of the 40Kh2N2MA steel with the subsequent electroslag remelting was investigated. It is shown that the use of such charge free from non-ferrous metal admixtures permits to increase an alloy hot ductility in the hot-brittleness range from 900 up to 1500 deg C. An increase of the deformation rate from 0.1 up to 1 s - 1 increases 1.5-3 times a level of minimum ductility within this temperature range. It is established that antimony and bismuth impurities considerably decrease hot ductility

  16. In situ grain fracture mechanics during uniaxial compaction of granular solids

    Science.gov (United States)

    Hurley, R. C.; Lind, J.; Pagan, D. C.; Akin, M. C.; Herbold, E. B.

    2018-03-01

    Grain fracture and crushing are known to influence the macroscopic mechanical behavior of granular materials and be influenced by factors such as grain composition, morphology, and microstructure. In this paper, we investigate grain fracture and crushing by combining synchrotron x-ray computed tomography and three-dimensional x-ray diffraction to study two granular samples undergoing uniaxial compaction. Our measurements provide details of grain kinematics, contacts, average intra-granular stresses, inter-particle forces, and intra-grain crystal and fracture plane orientations. Our analyses elucidate the complex nature of fracture and crushing, showing that: (1) the average stress states of grains prior to fracture vary widely in their relation to global and local trends; (2) fractured grains experience inter-particle forces and stored energies that are statistically higher than intact grains prior to fracture; (3) fracture plane orientations are primarily controlled by average intra-granular stress and contact fabric rather than the orientation of the crystal lattice; (4) the creation of new surfaces during fracture accounts for a very small portion of the energy dissipated during compaction; (5) mixing brittle and ductile grain materials alters the grain-scale fracture response. The results highlight an application of combined x-ray measurements for non-destructive in situ analysis of granular solids and provide details about grain fracture that have important implications for theory and modeling.

  17. Morphology Evolution on the Fracture Surface and Fracture Mechanisms of Multiphase Nanostructured ZrCu-Base Alloys

    Directory of Open Access Journals (Sweden)

    Feng Qiu

    2017-03-01

    Full Text Available A multiphase nanostructured ZrCu-base bulk alloy which showed a unique microstructure consisting of sub-micrometer scale Zr2Cu solid solution, nano-sized twinned plate-like ZrCu martensite (ZrCu (M, and retained ZrCu (B2 austenite was fabricated by copper mold casting. The observation of periodic morphology evolution on the fracture surface of the multiphase nanostructured ZrCu-base alloys has been reported, which suggested a fluctuant local stress intensity along the crack propagation. It is necessary to investigate the compressive deformation behavior and the fracture mechanism of the multiphase alloy and the relation to the unique microstructures. The results obtained in this study provide a better understanding of the deformation and fracture mechanisms of multiphase hybrid nanostructured ZrCu-based alloys and give guidance on how to improve the ductility/toughness of bulk ZrCu-based alloys.

  18. Neutron Diffraction Studies of Intercritically Austempered Ductile Irons

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-01-01

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

  19. Performance of heavy ductile iron castings for windmills

    Directory of Open Access Journals (Sweden)

    Iulian Riposan

    2010-05-01

    Full Text Available The main objective of the present paper is to review the specific characteristics and performance obtaining conditions of heavy ductile iron (DI castings, typically applied in windmills industry, such as hubs and rotor housings. The requirements for high impact properties in DI at low temperatures are part of the EN-GJS-400-18U-LT (SRN 1563 commonly referred to as GGG 40.3 (DIN 1693. Pearlitic influence factor (Px and antinodularising action factor (K1 were found to have an important influence on the structure and mechanical properties, as did Mn and P content, rare earth (RE addition and inoculation power. The presence of high purity pig iron in the charge is extremely beneficial, not only to control the complex factors Px and K1, but also to improve the ‘metallurgical quality’ of the iron melt. A correlation of C and Si limits with section modulus is very important to limit graphite nodule flotation. Chunky and surface-degenerated graphite are the most controlled graphite morphologies in windmills castings. The paper concluded on the optimum iron chemistry and melting procedure, Mg-alloys and inoculants peculiar systems, as well as on the practical solutions to limit graphite degeneration and to ensure castings of the highest integrity, typically for this field.

  20. Review on symmetric structures in ductile shear zones

    Science.gov (United States)

    Mukherjee, Soumyajit

    2017-07-01

    Symmetric structures in ductile shear zones range widely in shapes and geneses. Matrix rheology, its flow pattern, its competency contrast with the clast, degree of slip of the clast, shear intensity and its variation across shear zone and deformation temperature, and degree of confinement of clast in shear zones affects (independently) the degree of symmetry of objects. Kinematic vorticity number is one of the parameters that govern tail geometry across clasts. For example, symmetric and nearly straight tails develop if the clast-matrix system underwent dominantly a pure shear/compression. Prolonged deformation and concomitant recrystallization can significantly change the degree of symmetry of clasts. Angular relation between two shear zones or between a shear zone and anisotropy determines fundamentally the degree of symmetry of lozenges. Symmetry of boudinaged clasts too depends on competency contrast between the matrix and clast in some cases, and on the degrees of slip of inter-boudin surfaces and pure shear. Parasitic folds and post-tectonic veins are usually symmetric.

  1. Pearlitic ductile cast iron: damaging micromechanisms at crack tip

    Directory of Open Access Journals (Sweden)

    F. Iacoviello

    2013-07-01

    Full Text Available Ductile cast irons (DCIs are characterized by a wide range of mechanical properties, mainly depending on microstructural factors, as matrix microstructure (characterized by phases volume fraction, grains size and grain distribution, graphite nodules (characterized by size, shape, density and distribution and defects presence (e.g., porosity, inclusions, etc.. Versatility and higher performances at lower cost if compared to steels with analogous performances are the main DCIs advantages. In the last years, the role played by graphite nodules was deeply investigated by means of tensile and fatigue tests, performing scanning electron microscope (SEM observations of specimens lateral surfaces during the tests (“in situ” tests and identifying different damaging micromechanisms.In this work, a pearlitic DCIs fatigue resistance is investigated considering both fatigue crack propagation (by means of Compact Type specimens and according to ASTM E399 standard and overload effects, focusing the interaction between the crack and the investigated DCI microstructure (pearlitic matrix and graphite nodules. On the basis of experimental results, and considering loading conditions and damaging micromechanisms, the applicability of ASTM E399 standard on the characterization of fatigue crack propagation resistance in ferritic DCIs is critically analyzed, mainly focusing the stress intensity factor amplitude role.

  2. Quantifying Damage Accumulation During Ductile Plastic Deformation Using Synchrotron Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Suter, Robert M. [Carnegie Mellon Univ., Pittsburgh, PA (United States); Rollett, Anthony D. [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2015-08-15

    Under this grant, we have developed and demonstrated the ability of near-field High Energy Diffraction Microscopy (nf-HEDM) to map crystal orientation fields over three dimensions in deformed polycrystalline materials. Experimental work was performed at the Advanced Photon Source (APS) at beamline 1-ID. Applications of this new capability to ductile deformation of copper and zirconium samples were demonstrated as was the comparison of the experimental observations to computational plasticity models using a fast Fourier transform based algorithm that is able to handle the large experimental data sets. No such spatially resolved, direct comparison between measured and computed microstructure evolutions had previously been possible. The impact of this work is reflected in numerous publications and presentations as well as in the investments by DOE and DOD laboratories of millions of dollars in applying the technique, developing sophisticated new hardware that allows the technique to be applied to a wide variety of materials and materials problems, and in the use of the technique by other researchers. In essence, the grant facilitated the development of a new form of three dimensional microscopy and its application to technologically critical states of polycrystalline materials that are used throughout the U.S. and world economies. On-going collaborative work is further optimizing experimental and computational facilities at the APS and is pursuing expanded facilities.

  3. Thermomechanical Fatigue of Ductile Cast Iron and Its Life Prediction

    Science.gov (United States)

    Wu, Xijia; Quan, Guangchun; MacNeil, Ryan; Zhang, Zhong; Liu, Xiaoyang; Sloss, Clayton

    2015-06-01

    Thermomechanical fatigue (TMF) behaviors of ductile cast iron (DCI) were investigated under out-of-phase (OP), in-phase (IP), and constrained strain-control conditions with temperature hold in various temperature ranges: 573 K to 1073 K, 723 K to 1073 K, and 433 K to 873 K (300 °C to 800 °C, 450 °C to 800 °C, and 160 °C to 600 °C). The integrated creep-fatigue theory (ICFT) model was incorporated into the finite element method to simulate the hysteresis behavior and predict the TMF life of DCI under those test conditions. With the consideration of four deformation/damage mechanisms: (i) plasticity-induced fatigue, (ii) intergranular embrittlement, (iii) creep, and (iv) oxidation, as revealed from the previous study on low cycle fatigue of the material, the model delineates the contributions of these physical mechanisms in the asymmetrical hysteresis behavior and the damage accumulation process leading to final TMF failure. This study shows that the ICFT model can simulate the stress-strain response and life of DCI under complex TMF loading profiles (OP and IP, and constrained with temperature hold).

  4. A nonlinear CDM based damage growth law for ductile materials

    Science.gov (United States)

    Gautam, Abhinav; Priya Ajit, K.; Sarkar, Prabir Kumar

    2018-02-01

    A nonlinear ductile damage growth criterion is proposed based on continuum damage mechanics (CDM) approach. The model is derived in the framework of thermodynamically consistent CDM assuming damage to be isotropic. In this study, the damage dissipation potential is also derived to be a function of varying strain hardening exponent in addition to damage strain energy release rate density. Uniaxial tensile tests and load-unload-cyclic tensile tests for AISI 1020 steel, AISI 1030 steel and Al 2024 aluminum alloy are considered for the determination of their respective damage variable D and other parameters required for the model(s). The experimental results are very closely predicted, with a deviation of 0%-3%, by the proposed model for each of the materials. The model is also tested with predictabilities of damage growth by other models in the literature. Present model detects the state of damage quantitatively at any level of plastic strain and uses simpler material tests to find the parameters of the model. So, it should be useful in metal forming industries to assess the damage growth for the desired deformation level a priori. The superiority of the new model is clarified by the deviations in the predictability of test results by other models.

  5. Standard test methods for bend testing of material for ductility

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 These test methods cover bend testing for ductility of materials. Included in the procedures are four conditions of constraint on the bent portion of the specimen; a guided-bend test using a mandrel or plunger of defined dimensions to force the mid-length of the specimen between two supports separated by a defined space; a semi-guided bend test in which the specimen is bent, while in contact with a mandrel, through a specified angle or to a specified inside radius (r) of curvature, measured while under the bending force; a free-bend test in which the ends of the specimen are brought toward each other, but in which no transverse force is applied to the bend itself and there is no contact of the concave inside surface of the bend with other material; a bend and flatten test, in which a transverse force is applied to the bend such that the legs make contact with each other over the length of the specimen. 1.2 After bending, the convex surface of the bend is examined for evidence of a crack or surface irregu...

  6. Neoarchean ductile deformation of the Northeastern North China Craton: The Shuangshanzi ductile shear zone in Qinglong, eastern Hebei, North China

    Science.gov (United States)

    Liu, Boran; Neubauer, Franz; Liu, Junlai; Jin, Wei; Li, Weimin; Liang, Chenyue

    2017-05-01

    Archean granitic gneiss domes and greenstone belts are well-preserved in eastern North China Craton (NCC), one of the oldest Archean terrains in the world. The Shuangshanzi ductile shear zone in Qinglong, eastern Hebei Province is located between an Archean granitic gneiss dome and a greenstone belt within an uplift in eastern NCC. Supracrustal rocks from the Neoarchean Shuangshanzi and Zhuzhangzi Groups, and some Archean granitic gneisses were involved in the shearing along the eastern margin. In the southern part, the narrow NE-trending shear zone dips NW with dip angles of 40-60° and, in the northern part, the shear zone dips NWN with dip angles of 70-85°. Microstructural and EBSD fabric analyses suggest that the shear zone was developed at upper greenschist facies to lower amphibolite facies conditions with deformation temperatures of 400-550 °C. LA-ICP-MS zircon U-Pb dating of mylonitized granitic rocks and undeformed quartz diorite cutting the shear zone suggest that the Shuangshanzi ductile shear zone was formed between 2550 Ma and 2452 Ma. Detailed kinematic studies of the shear zone show a clear sinistral shear sense with a slightly oblique-slip component in the northern part and a sinistral transtensional slip component in the southern part. It is therefore suggested that the shear zone was formed during the Anziling doming with respect to the down-slipping Neoarchean Shuangshanzi and Zhuzhangzi Groups. The difference in kinematics along the southern and the northern sections is interpreted to be caused by the doming with an uneven clockwise spiral rotation. The BIF-rich supracrustal rocks have higher density than their neighboring granitic gneisses, and therefore can easily sink to form synclines by sagduction processes. The sagduction is mainly triggered by gravitational inversion of high density supracrustal rocks with respect to relatively light granitic gneisses within the dome. As a result, the gneisses synchronously moved upward. A shear zone

  7. On the influence of neutral turbulence on ambipolar diffusivities deduced from meteor trail expansion

    Directory of Open Access Journals (Sweden)

    C. M. Hall

    Full Text Available By measuring fading times of radar echoes from underdense meteor trails, it is possible to deduce the ambipolar diffusivities of the ions responsible for these radar echoes. It could be anticipated that these diffusivities increase monotonically with height akin to neutral viscosity. In practice, this is not always the case. Here, we investigate the capability of neutral turbulence to affect the meteor trail diffusion rate.

    Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence

  8. On the influence of neutral turbulence on ambipolar diffusivities deduced from meteor trail expansion

    Directory of Open Access Journals (Sweden)

    C. M. Hall

    2002-11-01

    Full Text Available By measuring fading times of radar echoes from underdense meteor trails, it is possible to deduce the ambipolar diffusivities of the ions responsible for these radar echoes. It could be anticipated that these diffusivities increase monotonically with height akin to neutral viscosity. In practice, this is not always the case. Here, we investigate the capability of neutral turbulence to affect the meteor trail diffusion rate.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence

  9. Numerical Analysis of AHSS Fracture in a Stretch-bending Test

    Science.gov (United States)

    Luo, Meng; Chen, Xiaoming; Shi, Ming F.; Shih, Hua-Chu

    2010-06-01

    Advanced High Strength Steels (AHSS) are increasingly used in the automotive industry due to their superior strength and substantial weight reduction advantage. However, their limited ductility gives rise to numerous manufacturing issues. One of them is the so-called `shear fracture' often observed on tight radii during stamping processes. Since traditional approaches, such as the Forming Limit Diagram (FLD), are unable to predict this type of fracture, efforts have been made to develop failure criteria that can predict shear fractures. In this paper, a recently developed Modified Mohr-Coulomb (MMC) ductile fracture criterion[1] is adopted to analyze the failure behavior of a Dual Phase (DP) steel sheet during stretch bending operations. The plasticity and ductile fracture of the present sheet are fully characterized by the Hill'48 orthotropic model and the MMC fracture model respectively. Finite Element models with three different element types (3D, shell and plane strain) were built for a Stretch Forming Simulator (SFS) test and numerical simulations with four different R/t ratios (die radius normalized by sheet thickness) were performed. It has been shown that the 3D and shell element models can accurately predict the failure location/mode, the upper die load-displacement responses as well as the wall stress and wrap angle at the onset of fracture for all R/t ratios. Furthermore, a series of parametric studies were conducted on the 3D element model, and the effects of tension level (clamping distance) and tooling friction on the failure modes/locations were investigated.

  10. Determination of ASTM 1016 structural welded joints fracture toughness through J integral

    International Nuclear Information System (INIS)

    Martins, Geraldo de Paula; Villela, Jefferson Jose; Terra, Jose Lucio; Rabello, Emerson Giovani; Martins, Geraldo Antonio Scoralick; Carneiro, Jose Rubens Goncalves

    2009-01-01

    Fracture toughness is an important parameter for studies of materials behavior in nuclear and conventional industry. Crack propagation resistance is, in general, evaluate using one of the fracture mechanics parameters K IC , for the case of the materials that exhibits a linear elastic behavior, the CTOD (crack tip opening displacement) and J IC , the critical value of J Integral, for the case of materials with elastic-plastic behavior. On this work the fracture mechanics parameters of the ASTM 1016 structural steel welded joints were obtained, using the J Integral. Charpy V tests at several temperatures were also obtained, with the purpose to obtain the curves of ductile-brittle of the regions of the welded joints: Base Metal, (MB), and Melted Zone (MZ). The joints were welded by Gas Metal Arc Welding (GMAW) with V bevel for evaluation the MZ toughness properties. The tests were accomplished at temperatures varying from -100 deg C to 100 deg C using the technical of compliance variation for J IC determination, the critical value that defines the initial stable crack growth, that applies to brittle and ductile materials. The J Integral alternative specimens has square cross section 10mmX10mm, according ASTM E 1820, with notch localized respectively at the BM and MZ. After the tests, the specimens fractured were analyzed in a scanning microscopic electronic (SME) for verification of the fracture surface. The fractography of the specimens at elevated temperatures presented dimples at the region of stable crack growth, characteristic of ductile fracture. The results of J Integral and Charpy V presented a good correlation between these two parameters. From these correlations it can be concluded that in some applications, the use Charpy V energy to infer fracture toughness can be substitute the Integral J tests. (author)

  11. The fracture behavior of an Al-Mg-Si alloy during cyclic fatigue

    International Nuclear Information System (INIS)

    Azzam, Diya; Menzemer, Craig C.; Srivatsan, T.S.

    2010-01-01

    In this paper, is presented and discussed the cyclic fracture behavior of the Al-Mg-Si alloy 6063 that is a candidate used in luminaire light poles. The light poles were subject to fatigue deformation. Test sections were taken from the failed region of the light pole and carefully examined in a scanning electron microscope with the objective of rationalizing the macroscopic fracture mode and intrinsic micromechanisms governing fracture under cyclic loading. The fatigue fracture surface of the alloy revealed distinct regions of early microscopic crack growth, stable crack growth and unstable crack growth and overload. An array of fine striations was found covering the regions of early and stable crack growth. Both macroscopic and fine microscopic cracks were found in the region of unstable crack growth. Very few microscopic voids and shallow dimples were evident on the fatigue fracture surface indicative of the limited ductility of the alloy under cyclic loading conditions.

  12. Distinct Fracture Patterns in Construction Steels for Reinforced Concrete under Quasistatic Loading— A Review

    Directory of Open Access Journals (Sweden)

    Fernando Suárez

    2018-03-01

    Full Text Available Steel is one of the most widely used materials in construction. Nucleation growth and coalescence theory is usually employed to explain the fracture process in ductile materials, such as many metals. The typical cup–cone fracture pattern has been extensively studied in the past, giving rise to numerical models able to reproduce this pattern. Nevertheless, some steels, such as the eutectoid steel used for manufacturing prestressing wires, does not show this specific shape but a flat surface with a dark region in the centre of the fracture area. Recent studies have deepened the knowledge on these distinct fracture patterns, shedding light on some aspects that help to understand how damage begins and propagates in each case. The numerical modelling of both fracture patterns have also been discussed and reproduced with different approaches. This work reviews the main recent advances in the knowledge on this subject, particularly focusing on the experimental work carried out by the authors.

  13. Draft fracture mechanics code case for American Society of Mechanical Engineers NUPACK rules

    Energy Technology Data Exchange (ETDEWEB)

    McConnell, P.; Sorenson, K. [Sandia National Labs., Albuquerque (United States); Nickell, R. [Applied Science and Technology, Poway (United States); Saegusa, T. [Central Research Inst. for Electric Power Industry, Abiko (Japan)

    2004-07-01

    The containment boundaries of most spent-fuel casks certified for use in the United States by the Nuclear Regulatory Commission are constructed with stainless steel, a material that is ductile in an engineering sense at all temperatures and for which, therefore, fracture mechanics principles are not relevant for the containment application. Ferritic materials may fail in a nonductile manner at sufficiently low temperatures, so fracture mechanics principles may be applied to preclude nonductile fracture. Because of the need to transport and store spent nuclear fuel safely in all types of climatic conditions, these vessels have regulatory lowest service temperatures that range down to -40 C (-40 F) for transport application. Such low service temperatures represent a severe challenge in terms of fracture toughness to many ferritic materials. Linear-elastic and elastic-plastic fracture mechanics principles provide a methodology for evaluating ferritic materials under such conditions.

  14. Deducing material quality in cast and hot-forged steels by new bending test

    Science.gov (United States)

    Valberg, Henry; Langøy, Morten; Nedreberg, Mette; Helvig, Torgeir

    2017-10-01

    A special bend test has been developed and applied for the purpose of characterization and comparison of the material ductility in crankpin steel discs manufactured by casting, or casting subsequently followed by hot open-die forging (ODF) or closed-die forging (CDF). The bending test specimen consists of a small rectangular plate of material with a round hole cut out in the middle. The "eye-shape" specimens were cut out from various positions either near to the surface of, or from the interior of the discs. The test method revealed differences in ductility for the investigated materials, and for different depth positions inside the discs. The roughening of the specimen surface on the top-side of the specimen bend also varied dependent on the processing method for the material. Current results show that this test method is useful for evaluation of material quality in differently processed material. Experimental bend test results are presented for differently processed variants of the same material, i.e., crankpin discs either made by solely casting or casting subsequently followed by hot working either by ODF or CDF.

  15. Coupling constants deduced for the resonances in kaon photo-production

    International Nuclear Information System (INIS)

    Cheoun, M. K.; Kim, K. S.; Choi, T. K.

    2004-01-01

    We deduced the coupling constants of nucleon and hyperon resonances, which participate in kaon productions as intermediate states that are formed by electro-magnetic probes and that finally decay into hadronic final states. We used an isobaric model based on an effective Lagrangian approach to describe the processes, in which relevant coupling constants regarding related resonances are effectively determined by fitting available experimental data. Our scheme to deduce the coupling constants was as follows: First, we calculated the lower and the upper limits on the coupling constants by using the experimental decay data available until now and/or theoretical predictions, such as those from quark models and SU(3) symmetry. Second, we exploited those limits as physical constraints on our fitting scheme for the kaon photo-production data. Finally, the deduced values and regions of the coupling constants, which satisfy not only the reaction data but also the decay data, are presented as figures with respect to the strong and the electro-magnetic coupling constants, and their multiplicative values. Our results for the coupling constants give physical values that are more restricted than those allowed by the experimental data nowadays.

  16. The DEDUCE Guided Query tool: providing simplified access to clinical data for research and quality improvement.

    Science.gov (United States)

    Horvath, Monica M; Winfield, Stephanie; Evans, Steve; Slopek, Steve; Shang, Howard; Ferranti, Jeffrey

    2011-04-01

    In many healthcare organizations, comparative effectiveness research and quality improvement (QI) investigations are hampered by a lack of access to data created as a byproduct of patient care. Data collection often hinges upon either manual chart review or ad hoc requests to technical experts who support legacy clinical systems. In order to facilitate this needed capacity for data exploration at our institution (Duke University Health System), we have designed and deployed a robust Web application for cohort identification and data extraction--the Duke Enterprise Data Unified Content Explorer (DEDUCE). DEDUCE is envisioned as a simple, web-based environment that allows investigators access to administrative, financial, and clinical information generated during patient care. By using business intelligence tools to create a view into Duke Medicine's enterprise data warehouse, DEDUCE provides a Guided Query functionality using a wizard-like interface that lets users filter through millions of clinical records, explore aggregate reports, and, export extracts. Researchers and QI specialists can obtain detailed patient- and observation-level extracts without needing to understand structured query language or the underlying database model. Developers designing such tools must devote sufficient training and develop application safeguards to ensure that patient-centered clinical researchers understand when observation-level extracts should be used. This may mitigate the risk of data being misunderstood and consequently used in an improper fashion. Copyright © 2010 Elsevier Inc. All rights reserved.

  17. The DEDUCE Guided Query Tool: Providing Simplified Access to Clinical Data for Research and Quality Improvement

    Science.gov (United States)

    Horvath, Monica M.; Winfield, Stephanie; Evans, Steve; Slopek, Steve; Shang, Howard; Ferranti, Jeffrey

    2011-01-01

    In many healthcare organizations, comparative effectiveness research and quality improvement (QI) investigations are hampered by a lack of access to data created as a byproduct of patient care. Data collection often hinges upon either manual chart review or ad hoc requests to technical experts who support legacy clinical systems. In order to facilitate this needed capacity for data exploration at our institution (Duke University Health System), we have designed and deployed a robust Web application for cohort identification and data extraction—the Duke Enterprise Data Unified Content Explorer (DEDUCE). DEDUCE is envisioned as a simple, web-based environment that allows investigators access to administrative, financial, and clinical information generated during patient care. By using business intelligence tools to create a view into Duke Medicine's enterprise data warehouse, DEDUCE provides a guided query functionality using a wizard-like interface that lets users filter through millions of clinical records, explore aggregate reports, and, export extracts. Researchers and QI specialists can obtain detailed patient- and observation-level extracts without needing to understand structured query language or the underlying database model. Developers designing such tools must devote sufficient training and develop application safeguards to ensure that patient-centered clinical researchers understand when observation-level extracts should be used. This may mitigate the risk of data being misunderstood and consequently used in an improper fashion. PMID:21130181

  18. Statistical fatigue properties of ductile cast irons; Kyujo kokuen chutetsu no hiro kyodo no tokeiteki seishitsu

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, N.; Nishikawa, Y.; Inaba, K. [Gifu University, Gifu (Japan). Faculty of Engineering; Fukuyama, K. [Gifu Prefectural Police Headquarters, Gifu (Japan)

    1995-09-15

    Rotating bending fatigue tests of smooth specimens were carried out at room temperature on a pearlitic ductile cast iron (PDI) and austempered ductile cast iron (ADI). No significant difference due to sampling position from cast blocks in both materials was found in fatigue limit and fatigue life distribution. Then, the statistical fatigue properties of ferritic (FDI), ferritic/pearlitic (FPDI), pearlitic and austempered ductile cast irons were investigated. The fatigue life distributions of all ductile irons were well represented by the three parameter Weibull distribution modified by the saturated probability of failure. The shape parameters of FDI, FPDI and PDI were in proportion to {sigma}/{sigma}w independent on micro structure, while the shape parameters of both stress levels in ADI were smaller than unity. The fatigue strength of ADI was highest, but the scatter of fatigue life was largest among the all cast irons. 13 refs., 15 figs., 7 tabs.

  19. Ductile electroless Ni-P coating onto flexible printed circuit board

    Science.gov (United States)

    Wang, Wenchang; Zhang, Weiwei; Wang, Yurong; Mitsuzak, Naotoshi; Chen, Zhidong

    2016-03-01

    In this study, a ductile electroless Ni-P coating on the flexible printed circuit board (FPCB) was prepared in an acidic nickel plating bath. The addition of dipropylamine (DPA) in electroless plating not only improves the ductility of the Ni-P coating, but also enhances the corrosion resistance. The further analysis reveals that the ductility improvement and enhancement of corrosion resistance for the Ni-P coating may be due to the fact that the addition of DPA significantly refines the volume of columnar nodule and reduce the porosity, thus leading to the released internal stress. In addition, it was found that the nodule within the Ni-P coating grew into a columnar structure, which may be also contribute to the improvement of ductility.

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

    Directory of Open Access Journals (Sweden)

    Alan Vaško

    2009-10-01

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

  1. Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride

    Science.gov (United States)

    2015-08-01

    Aluminum Nitride by GA Gazonas and JW McCauley Weapons and Materials Research Directorate, ARL JJ Guo, KM Reddy, A Hirata, T Fujita, and MW Chen...Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...their microscopic structure. In this study, we report a size induced brittle-to-ductile transition in single-crystal aluminum nitride (AlN). When the

  2. Ductile cast iron obtaining by Inmold method with use of LOST FOAM process

    Directory of Open Access Journals (Sweden)

    T. Pacyniak

    2010-01-01

    Full Text Available The possibility of manufacturing of ductile cast iron castings by Inmold method with use of LOST FOAM process was presented in this work. The spheroidization was carried out by magnesium master alloy in amounts of 1% casting mass. Nodulizer was located in the reactive chamber in the gating system made of foamed polystyrene. Pretests showed, that there are technical possibilities of manufacturing of casts from ductile cast iron in the LOST FOAM process with use of spheroidization in mould.

  3. Effects of casting defects, matrix structures and loading conditions on the fatigue strength of ductile irons

    Directory of Open Access Journals (Sweden)

    Endo Masahiro

    2014-06-01

    Full Text Available A novel method is presented to estimate the lower bound of the scatter in fatigue limit of ductile iron based upon the information of microstructural in homogeneities and loading conditions. The predictive capability of the method was verified by comparing to the experimental data obtained by the rotating-bending, torsion and combined tension-torsion fatigue tests for ductile irons with ferritic, pearlitic and bulls-eye (ferritic/pearlitic microstructures.

  4. Effects of ductile matrix failure in three dimensional analysis of metal matrix composites

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    1998-01-01

    Full three dimensional numerical cell model analyses are carried out for a metal reinforced by short fibers, to study the development of ductile matrix failure. A porous ductile material model is used to describe the effect of the nucleation and growth of voids to coalescence. In each case studied...... a rounded vertex on the yield surface. The full three dimensional model is used to study effects of deviations from equal transverse tension in directions perpendicular to the fibers. (C) 1998 Acta Metallurgica Inc....

  5. Radionuclide transport in fractured media

    International Nuclear Information System (INIS)

    Williams, M.M.R.

    1993-01-01

    Until recently, the classical advective-dispersive transport equation was considered to be an adequate model for describing the motion of a solute (e.g. radionuclides) in porous and fractured media. In this model, the dispersion coefficient is either obtained from a microscopic model of the porous medium or by carefully controlled experiments. As a result of such experiments, a large body of data has been accumulated on the dispersivity. Detailed examination of these data has resulted in a curious phenomenon being discovered; namely, that the longitudinal dispersion length is 'scale-dependent'. That is to say the value deduced depends on the 'size' of the experiment, i.e. on the distance over which measurements are made. Several interesting attempts have been made to develop theories which explain this phenomenon, all based on treating the velocity of the water in the porous medium as a spatially random variable, but retaining the advective-dispersive balance equation. In this work we present an entirely new approach to the problem of solute transport in fractured media based upon an analogy with neutron transport. The new method has several advantages over the previous theories and these will be explained below. Results from the new theory are in agreement with experimental trends and do not require any further adjustment to explain the scale-dependent effect

  6. Degradation of impact fracture during accelerated aging of weld metal on microalloyed steel; Degradacion de la tenacidad al impacto durante el envejecimiento acelerado de soldadura en acero microaleado

    Energy Technology Data Exchange (ETDEWEB)

    Vargas-Arista, B.; Hallen, J. M.; Albiter, A.; Angeles-Chavez, C.

    2008-07-01

    The effect of accelerated aging on the toughness and fracture of the longitudinal weld metal on an API5L-X52 line pipe steel was evaluated by Charpy V-notch impact test, fracture analysis and transmission electron microscopy. Aging was performed at 250 degree centigrade for 100 to 1000 h. The impact results indicated a significant reduction in the fracture energy and impact toughness as a function of aging time, which were achieved by the scanning electron microscope fractography that showed a decrease in the vol fraction of microvoids by Charpy ductile failure with the aging time, which favored the brittle fracture by transgranular cleavage. The minimum vol fraction of microvoids was reached at 500 h due to the peak aged. The microstructural analysis indicated the precipitation of transgranular iron nano carbides in the aged specimens, which was related to the deterioration of toughness and change in the ductile to brittle behavior. (Author) 15 refs.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-05-01

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

  8. Effect of Rare Earth Yttrium on the Hot Ductility of Fe-36Ni Invar Alloy

    Science.gov (United States)

    Yu, Y. C.; Liu, H. T.; Chen, W. Q.; Zheng, H. G.

    2014-12-01

    The hot ductility of Fe-36Ni invar alloy doped with and without yttrium was investigated using a Gleeble-3800 thermal-mechanical simulator over the temperature range 850-1050 °C and the improvement mechanism of the hot ductility was analysed with a combination of SEM, EDS and OM. The results showed that Fe-36Ni invar alloy had a poor hot ductility below 1050 °C, which was mainly attributed to the presence of the grain boundary sliding and weak grain boundaries. The addition of 0.048% yttrium had a substantial improvement in the hot ductility of Fe-36Ni invar alloy over the whole testing temperature range especially at 950-1000 °C. At 850-900 °C, the improvement of the hot ductility was mainly associated with the grain boundary strengthening and the restriction of the grain boundary sliding because the addition of yttrium could reduce the segregation of sulfur at grain boundaries and refine the grain structure. At 950-1000 °C, the hot ductility was highly improved, which was owed to the acceleration and occurrence of dynamic recrystallization as a result of the refinement of the grain structure by addition of yttrium.

  9. Size and constraint effects on mechanical and fracture behavior of micro-scale Ni/Sn3.0Ag0.5Cu/Ni solder joints

    Energy Technology Data Exchange (ETDEWEB)

    Qin, H.B. [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Zhang, X.P., E-mail: mexzhang@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Zhou, M.B.; Zeng, J.B. [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Mai, Y.-W. [Centre for Advanced Materials Technology (CAMT), School of Aerospace, Mechanical and Mechatronic Engineering J07, The University of Sydney, NSW 2006 (Australia)

    2014-11-03

    Solder joints are generally regarded as the weakest part in packaging systems and electronic assemblies in modern electronic products and devices. In this study, both experimental and finite element methods were used to characterize the mechanical behavior of micro-scale Ni/Sn3.0Ag0.5Cu/Ni sandwich-structured joints with different thickness-to-diameter ratios (R varying from 1/3 to 1/12) under quasi-static tension loading using a dynamic mechanical analyzer (DMA). Experimental results show that crack initiation and propagation in the solder matrix occur in a typical ductile manner. Compared with Cu/Sn3.0Ag0.5Cu/Cu sandwich-structured solder joints, Ni/Sn3.0Ag0.5Cu/Ni solder joints have much higher tensile strengths due to the dispersion strengthening effect through the fine Ag{sub 3}Sn particles. With decreasing R, both stiffness and tensile strength of solder joints increase obviously with decreasing coefficient of stress state and damage equivalent stress. Moreover, results of quantitative fractographic analysis by SEM and EDS display three fracture modes with decreasing R. Joints with R≥1/4 all fail by ductile fracture, those with R=1/6 fail by either ductile fracture or mixed ductile and brittle fractures, and for joints with R=1/12, brittle fracture is dominant. Furthermore, results obtained have also shown that the crack growth driving forces, K{sub I} and K{sub II}, as well as the strain energy release rate, G{sub I}, in the Ni{sub 3}Sn{sub 4} layer and at the Ni{sub 3}Sn{sub 4}/Ni interface, increase significantly with decreasing R. Hence, under tensile loading the fracture mode of solder joints changes from ductile to brittle as R is decreased.

  10. Effects of fast neutron irradiation on the fracture behavior of stainless steel

    International Nuclear Information System (INIS)

    Huang, F.H.; Fish, R.L.

    1982-03-01

    In designing against premature fracture, the characteristics of materials must be measured and design criteria developed. The reduction in ductility for irradiated stainless steels has been observed, but little work has been conducted on evaluating the effects of notches on these materials. A reduction in notch ductility has been investigated in Charpy-V impact tests of irradiated Type 304 and Type 316 stainless steel; in irradiated Type 304 stainless steel, notch effects were not observed at 232 and 317 0 C, but as the test temperature was increased from 538 to 593 0 C, the material irradiated to a fluence of 3 X 10 22 n/cm 2 exhibited a notch weakening. Recently, similar experiments were performed on irradiated 20% cold worked Type 316 stainless steel to determine the effects of irradiation on the fracture behavior of this alloy

  11. Superplastic Grade Titanium Alloy: Comparative Evaluation of Mechanical Properties, Microstructure, and Fracture Behavior

    Directory of Open Access Journals (Sweden)

    K. V. Sudhakar

    2016-01-01

    Full Text Available In this investigation, static fracture, microstructure, and the mechanical behavior of SP-700 alloy (a superplastic grade were evaluated and compared with two other titanium alloys. The comparisons were made in terms of suitably designed heat treatment cycles. The heat treatment cycles included annealing and a combination of solutionizing and aging treatments for all three alloys. Tensile properties were determined using MTS Landmark Servohydraulic Test System. Tensile tested samples’ fracture surfaces were investigated with LEO-VP SEM instrument. Ti-15-3-3-3 alloy exhibited relatively a higher combination of strength and ductility in comparison to the other two alloys. All three types of titanium alloys demonstrated a very good level of tensile strength and ductility suitable for applications in military and biomedical fields.

  12. Effects of Laser Quenching on Impact Toughness and Fracture Morphologies of 40CrNiMo High Strength Steel

    Science.gov (United States)

    Dejun, Kong; Lei, Zhang

    2014-10-01

    The surface of 40CrNiMo steel was quenched with a CO2 laser, Charpy impact test was conducted at temperatures of 20, 0, and -20 °C, and the impact absorption energies were measured. The fracture morphologies were observed with SEM, and the influence of microhardness, residual stress, and retained austenite on mechanical behavior of impact fracture after laser quenching was discussed. The results show that the hardened layer depth is more than 1 mm after laser quenching, and hardness is about 480-500 HV. The fracture morphology of the sample is dimple rupture at a temperature of 20 °C; with the lower temperature the fracture dimples become smaller. At a temperature of -20 °C, the fracture morphologies change from ductile to brittle, which is mainly cleavage fracture. The increase in surface hardness, production of compressive residual stress, and existence of retained austenite after laser quenching are the main mechanisms of increasing impact toughness.

  13. Size Effects on Deformation and Fracture of Scandium Deuteride Films.

    Energy Technology Data Exchange (ETDEWEB)

    Teresi, C. S. [Univ. of Minnesota, Minneapolis, MN (United States); Hintsala, E. [Univ. of Minnesota, Minneapolis, MN (United States); Hysitron, Inc., Eden Prairie, MN (United States); Adams, David P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Yang, Nancy Y. C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kammler, Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Moody, N. R. [Univ. of Minnesota, Minneapolis, MN (United States); Gerberich, W. W. [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-07-01

    Metal hydride films have been observed to crack during production and use, prompting mechanical property studies of scandium deuteride films. The following focuses on elastic modulus, fracture, and size effects observed in the system for future film mechanical behavior modeling efforts. Scandium deuteride films were produced through the deuterium charging of electron beam evaporated scandium films using X-ray diffraction, scanning Auger microscopy, and electron backscatter diffraction to monitor changes in the films before and after charging. Scanning electron microscopy, nanoindentation, and focused ion beam machined micropillar compression tests were used for mechanical characterization of the scandium deuteride films. The micropillars showed a size effect for flow stress, indicating that film thickness is a relevant tuning parameter for film performance, and that fracture was controlled by the presence of grain boundaries. Elastic modulus was determined by both micropillar compression and nanoindentation to be approximately 150 GPa, Fracture studies of bulk film channel cracking as well as compression induced cracks in some of the pillars yielded a fracture toughness around 1.0 MPa-m1/2. Preliminary Weibull distributions of fracture in the micropillars are provided. Despite this relatively low value of fracture toughness, scandium deuteride micropillars can undergo a large degree of plasticity in small volumes and can harden to some degree, demonstrating the ductile and brittle nature of this material

  14. Prediction of fracture forming limit for DP780 steel sheet

    Science.gov (United States)

    Lou, Yanshan; Lim, Sung Jun; Huh, Hoon

    2013-07-01

    This paper is concerned with modeling of fracture strains of DP780 using a newly proposed micro-mechanism-motivated ductile fracture criterion (Lou et al., 2012) and its application to predict limit dome heights (LDH) for nine hemispherical punch-stretch tests. Dog-bone specimens are tested to characterize strain hardening behavior. Five arc-shaped specimens and four square-shaped specimens are drawn until fracture to construct a fracture forming limit diagram (FFLD) using circle grid analysis. Fracture strains are approximated from constructed FFLD in uniaxial, plane strain and balanced biaxial tension. The approximated fracture strains are employed to calculate material constants of the proposed criterion as well as six conventional criteria. FFLDs predicted by these criteria are compared with experimental results. The comparison demonstrates that only the proposed criterion describes FFLD perfectly from uniaxial tension to balanced biaxial tension. All criteria are implemented into ABAQUS/Explicit to predict LDHs of punch-stretch tests. Numerical results indicate that LDHs are severely underestimated for the square-shaped specimens by conventional criteria while the proposed criterion predicts LDHs with good agreement for nine tests with strain paths between uniaxial tension and balanced biaxial tension. Thus, the proposed criterion is recommended to access formability from uniaxial tension to balanced biaxial tension.

  15. Interim report on the fracture toughness of 2 1/4 Cr-1 Mo steel and weldments at elevated temperatures

    International Nuclear Information System (INIS)

    Yuen, J.L.; Roy, P.

    1980-01-01

    The Reference Nil Ductility Temperature (RT/sub NDT) for the base material and weldments tested range from -7 0 C (20 0 F) to 38 0 C (100 0 F). Fracture toughness results at room temperature fall above the ASME Code K/sub IR/ curve for all material conditions. Elevated temperature fracture toughness tests up to 510 0 C (950 0 F) decrease with increasing temperature and fall below the current code assumption for the K/sub IR/ curve at elevated temperatures. At 510 0 C (950 0 F), the thermally aged base material yielded the lowest fracture toughness values for the conditions tested

  16. Evidence for seismogenic fracture of silicic magma.

    Science.gov (United States)

    Tuffen, Hugh; Smith, Rosanna; Sammonds, Peter R

    2008-05-22

    It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of approximately 600 degrees C (ref. 1). This thinking underpins our understanding of volcanic earthquakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle-ductile fault textures in silicic lavas has led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? Here we deform high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting.

  17. Structural and temporal evolution of a reactivated brittle-ductile fault - Part I: Fault architecture, strain localization mechanisms and deformation history

    Science.gov (United States)

    Torgersen, E.; Viola, G.

    2014-12-01

    Faults are by nature dynamic, as their architecture and composition evolve progressively in space and through time steered by the interplay between strain weakening and hardening mechanisms. This study combines structural analysis, geochemistry and chlorite geothermometry to investigate deformation and strain localization mechanisms of the Kvenklubben fault, a Paleozoic brittle-ductile thrust in northern Norway, with the goal to constrain their temporal variations and the consequences thereof on fault architecture development and rheological behavior. The fault evolved from an initially discrete brittle feature slipping mainly by seismogenic ruptures to a wide brittle-ductile phyllonite deforming by aseismic creep. The formation of mechanically weak phyllosilicates by decarbonation of footwall dolostones and carbonation of hanging wall metabasalts was the main weakening mechanism, whereas partitioning of fluid flow and fracture sealing following transient high pore pressure-driven embrittlement caused episodic and localized strain hardening. The interplay between strain weakening and hardening mechanisms caused the fault core to widen. We suggest that the ability for carbonate-hosted faults to slip by seismogenic rupture is also a function of the faults' structural-evolutionary stage, and that it decreases progressively with fault maturity. This study demonstrates the importance of calibrating the present-day fault anatomy against the dynamic character of faults, which evolve geometrically, compositionally and mechanically in space and through time.

  18. Mechanical milling of a nano structured ductile iron powder under dry, wet and cryogenic atmospheres; Proceso de molturacion mecanica en medio seco, humedo y criogenico de polvo de hierro ductil nanoestructurado

    Energy Technology Data Exchange (ETDEWEB)

    Cinca, N.; Hurtado, E.; Cano, I. G.; Guilemany, J. M.

    2011-07-01

    The main objective of this study, is to obtain an effective particle and grain size reduction of a nano structured iron powder by mechanical milling under different milling media. One of the main challenges in this study is to work with this material of great ductility.The variables of the study to be optimized have been the following: speed of rotation, powder to ball ratio (PBR) and the percentage of control agent to induce an effective powder fracturing in front of cold welding. The powder has been characterized by a Laser Diffraction Particle Size Analyser, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and, X-ray diffraction.Through the comparative study, it is found that operating under dry milling conditions: there is a more effective particle size reduction of 43 % and grain size reduction of 62 %. In wet conditions has been reduced the amount of oxide, as well as to obtain a more homogenous distribution of the resulting powder. The results under cryogenic media is presented as promising. (Author) 15 refs.

  19. Fracture model for structured quasibrittle materials

    Science.gov (United States)

    Kurguzov, V. D.; Astapov, N. S.; Astapov, I. S.

    2014-11-01

    We analyze the applicability of a modified Leonov-Panasyuk-Dugdale model to the description of the propagation of a mode I crack in structured materials under plane stress conditions. For quasi-brittle materials, refined formulas of the critical length of the prefracture zone and the critical load containing a structural parameter are proposed. The Kornev model is extended to the case of quasi-ductile materials. Numerical simulation of plastic zones in square plates of a bimetal and a homogeneous material under quasi-static loading is performed. In the numerical model, the equations of deformable solid mechanics are expressed in the Lagrangian formulation, which is the most preferred for large-strain deformations of elastoplastic materials. The results of the numerical experiments are consistent with the results of calculations using the analytical model for the fracture of structured materials.

  20. Numerical modelling in non linear fracture mechanics

    Directory of Open Access Journals (Sweden)

    Viggo Tvergaard

    2007-07-01

    Full Text Available Some numerical studies of crack propagation are based on using constitutive models that accountfor damage evolution in the material. When a critical damage value has been reached in a materialpoint, it is natural to assume that this point has no more carrying capacity, as is done numerically in the elementvanish technique. In the present review this procedure is illustrated for micromechanically based materialmodels, such as a ductile failure model that accounts for the nucleation and growth of voids to coalescence, and a model for intergranular creep failure with diffusive growth of grain boundary cavities leading to micro-crack formation. The procedure is also illustrated for low cycle fatigue, based on continuum damage mechanics. In addition, the possibility of crack growth predictions for elastic-plastic solids using cohesive zone models to represent the fracture process is discussed.

  1. Reliability Analysis of Fatigue Fracture of Wind Turbine Drivetrain Components

    DEFF Research Database (Denmark)

    Berzonskis, Arvydas; Sørensen, John Dalsgaard

    2016-01-01

    in the volume of the casted ductile iron main shaft, on the reliability of the component. The probabilistic reliability analysis conducted is based on fracture mechanics models. Additionally, the utilization of the probabilistic reliability for operation and maintenance planning and quality control is discussed....... of operation and maintenance. The manufacturing of casted drivetrain components, like the main shaft of the wind turbine, commonly result in many smaller defects through the volume of the component with sizes that depend on the manufacturing method. This paper considers the effect of the initial defect present...

  2. The Rheological Evolution of Brittle-Ductile Transition Rocks During the Earthquake Cycle: Evidence for a Ductile Precursor to Pseudotachylyte in an Extensional Fault System, South Mountains, Arizona

    Science.gov (United States)

    Stewart, Craig A.; Miranda, Elena A.

    2017-12-01

    We investigate how the rheological evolution of shear zone rocks from beneath the brittle-ductile transition (BDT) is affected by coeval ductile shear and pseudotachylyte development associated with seismicity during the earthquake cycle. We focus our study on footwall rocks of the South Mountains core complex, and we use electron backscatter diffraction (EBSD) analyses to examine how strain is localized in granodiorite mylonites both prior to and during pseudotachylyte development beneath the BDT. In mylonites that are host to pseudotachylytes, deformation is partitioned into quartz, where quartz exhibits crystallographic-preferred orientation patterns and microstructures indicative of dynamic recrystallization during dislocation creep. Grain size reduction during dynamic recrystallization led to the onset of grain boundary sliding (GBS) accommodated by fluid-assisted grain size-sensitive (GSS) creep, localizing strain in quartz-rich layers prior to pseudotachylyte development. The foliation-parallel zones of GBS in the host mylonites, and the presence of GBS traits in polycrystalline quartz survivor clasts indicate that GBS zones were the ductile precursors to in situ pseudotachylyte generation. During pseudotachylyte development, strain was partitioned into the melt phase, and GSS deformation in the survivor clasts continued until crystallization of melt impeded flow, inducing pseudotachylyte development in other GBS zones. We interpret the coeval pseudotachylytes with ductile precursors as evidence of seismic events near the BDT. Grain size piezometry yields high differential stresses in both host mylonites ( 160 MPa) and pseudotachylyte survivor clasts (> 200 MPa), consistent with high stresses during interseismic and coseismic phases of the earthquake cycle, respectively.

  3. A fracture mechanics study of tungsten failure under high heat flux loads

    International Nuclear Information System (INIS)

    Li, Muyuan

    2015-01-01

    The performance of fusion devices is highly dependent on plasma-facing components. Tungsten is the most promising candidate material for armors in plasma-facing components in ITER and DEMO. However, the brittleness of tungsten below the ductile-to-brittle transition temperature is very critical to the reliability of plasma-facing components. In this work, thermo-mechanical and fracture behaviors of tungsten are predicted numerically under fusion relevant thermal loadings.

  4. Modeling of Damage Evolution and Fracture in 5182 H111 Aluminum Alloy

    OpenAIRE

    Abdelouahid, EL Amri; haddou, Mounir El Yakhloufi; Abdelatif, El Khamlichi

    2015-01-01

    This paper presents results of a numerical modeling of ductile fracture and failure of elements made of 5182H111 aluminum alloys subjected to dynamic traction. The analysis was performed using Johnson-Cook model based on ABAQUS software. The aim of the research was to specify and test the mechanical properties during numerical simulations. The experimental test results for the mechanical properties of the studies for steel were presented with a large description of the testing facilities. The...

  5. Evaluation of the ductile-to-brittle transition temperature of a silicon steel under various strain rate conditions with a servo-hydraulic high speed testing machine

    Science.gov (United States)

    Kwon, Junbeom; Huh, Hoon; Kim, Jae-song

    2017-07-01

    This paper is concerned with the construction of an empirical model of the Ductile-to-Brittle Transition Temperature (DBTT) for 3.4% silicon steel based on tensile test results at strain rates ranging from 0.001 s‒1 to 100 s‒1. Dynamic tensile tests are conducted using an in-house servo hydraulic tensile test machine at strain rates of 1 s‒1, 10 s‒1, and 100 s‒1 and quasi-static tensile tests are conducted using Instron 4206 at strain rates of 0.001 s‒1 and 0.01 s‒1 with an environmental chamber. Fracture elongations are measured by a DIC method during all tests using the high-speed camera for accurate measurement. The DBTT of 3.4% silicon steel is presented in terms of fracture strain with the variation of the temperature and the strain rate. It is demonstrated from the test results that the DBTT increases as the strain rate increases. An empirical model of the DBTT is constructed in terms of strain rate, temperature and fracture elongation. The parameters of the empirical model are calculated from experimental results obtained at various temperatures and strain rates.

  6. A Predictive Framework for Thermomechanical Fatigue Life of High Silicon Molybdenum Ductile Cast Iron Based on Considerations of Strain Energy Dissipation

    Science.gov (United States)

    Avery, Katherine R.

    Isothermal low cycle fatigue (LCF) and anisothermal thermomechanical fatigue (TMF) tests were conducted on a high silicon molybdenum (HiSiMo) cast iron for temperatures up to 1073K. LCF and out-of-phase (OP) TMF lives were significantly reduced when the temperature was near 673K due to an embrittlement phenomenon which decreases the ductility of HiSiMo at this temperature. In this case, intergranular fracture was predominant, and magnesium was observed at the fracture surface. When the thermal cycle did not include 673K, the failure mode was predominantly transgranular, and magnesium was not present on the fracture surface. The in-phase (IP) TMF lives were unaffected when the thermal cycle included 673K, and the predominant failure mode was found to be transgranular fracture, regardless of the temperature. No magnesium was present on the IP TMF fracture surfaces. Thus, the embrittlement phenomenon was found to contribute to fatigue damage only when the temperature was near 673K and a tensile stress was present. To account for the temperature- and stress-dependence of the embrittlement phenomenon on the TMF life of HiSiMo cast iron, an original model based on the cyclic inelastic energy dissipation is proposed which accounts for temperature-dependent differences in the rate of fatigue damage accumulation in tension and compression. The proposed model has few empirical parameters. Despite the simplicity of the model, the predicted fatigue life shows good agreement with more than 130 uniaxial low cycle and thermomechanical fatigue tests, cyclic creep tests, and tests conducted at slow strain rates and with hold times. The proposed model was implemented in a multiaxial formulation and applied to the fatigue life prediction of an exhaust manifold subjected to severe thermal cycles. The simulation results show good agreement with the failure locations and number of cycles to failure observed in a component-level experiment.

  7. Elongational rheology and cohesive fracture of photo-oxidated LDPE

    International Nuclear Information System (INIS)

    Rolón-Garrido, Víctor H.; Wagner, Manfred H.

    2014-01-01

    It was found recently that low-density polyethylene (LDPE) samples with different degrees of photo-oxidation represent an interesting system to study the transition from ductile to cohesive fracture and the aspects of the cohesive rupture in elongational flow. Sheets of LDPE were subjected to photo-oxidation in the presence of air using a xenon lamp to irradiate the samples for times between 1 day and 6 weeks. Characterisation methods included Fourier transform infrared spectroscopy, solvent extraction method, and rheology in shear and uniaxial extensional flows. Linear viscoelasticity was increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by the carbonyl index, acid and aldehydes groups, and gel fraction. The molecular stress function model was used to quantify the experimental data, and the nonlinear model parameter β was found to be correlated with the gel content. The uniaxial data showed that the transition from ductile to cohesive fracture was shifted to lower elongational rates, the higher the gel content was. From 2 weeks photo-oxidation onwards, cohesive rupture occurred at every strain rate investigated. The true strain and true stress at cohesive fracture as well as the energy density applied to the sample up to fracture were analyzed. At low gel content, rupture was mainly determined by the melt fraction while at high gel content, rupture occurred predominantly in the gel structure. The strain at break was found to be independent of strain rate, contrary to the stress at break and the energy density. Thus, the true strain and not the stress at break or the energy density was found to be the relevant physical quantity to describe cohesive fracture behavior of photo-oxidated LDPE. The equilibrium modulus of the gel structures was correlated with the true strain at rupture. The stiffer the gel structure, the lower was the deformation tolerated before the sample breaks

  8. Determination of the onset of ductile crack extension in 2 1/4 Cr 1 Mo steel by multi-specimen J integral testing

    International Nuclear Information System (INIS)

    Druce, S.G.

    1982-02-01

    Results obtained at AERE Harwell as part of the first phase of the European Group on Fracture round robin activity into ductile crack initiation detection are presented and discussed. Data are analysed using the current ASTM Jsub(IC) testing procedure and by an alternative procedure. Difficulties in the definition of 'initiation' are highlighted and deficiencies of the ASTM procedure exposed. The ASTM Jsub(IC) value for 2 1/4 Cr 1 Mo steel was determined as 0.21 MN/m. The alternative procedure provides a more accurate evaluation of the 'initiation' value of J, that is, at the point of crack advance in excess of that due to crack tip blunting. Using this procedure the 'initiation' value, Jsub(i), was measured as 0.14 MN/m. (author)

  9. Surface deformation and friction characteristic of nano scratch at ductile-removal regime for optical glass BK7.

    Science.gov (United States)

    Li, Chen; Zhang, Feihu; Ding, Ye; Liu, Lifei

    2016-08-20

    Nano scratch for optical glass BK7 based on the ductile-removal regime was carried out, and the influence rule of scratch parameters on surface deformation and friction characteristic was analyzed. Experimental results showed that, with increase of normal force, the deformation of burrs in the edge of the scratch was more obvious, and with increase of the scratch velocity, the deformation of micro-fracture and burrs in the edge of the scratch was more obvious similarly. The residual depth of the scratch was measured by atomic force microscope. The experimental results also showed that, with increase of normal force, the residual depth of the scratch increased linearly while the elastic recovery rate decreased. Furthermore, with increase of scratch velocity, the residual depth of the scratch decreased while the elastic recovery rate increased. The scratch process of the Berkovich indenter was divided into the cutting process of many large negative rake faces based on the improved cutting model, and the friction characteristic of the Berkovich indenter and the workpiece was analyzed. The analysis showed that the coefficient of friction increased and then tended to be stable with the increase of normal force. Meanwhile, the coefficient of friction decreased with the increase of scratch velocity, and the coefficients, k ln(v) and μ0, were introduced to improve the original formula of friction coefficient.

  10. Fracturing and brittleness index analyses of shales

    Science.gov (United States)

    Barnhoorn, Auke; Primarini, Mutia; Houben, Maartje

    2016-04-01

    The formation of a fracture network in rocks has a crucial control on the flow behaviour of fluids. In addition, an existing network of fractures , influences the propagation of new fractures during e.g. hydraulic fracturing or during a seismic event. Understanding of the type and characteristics of the fracture network that will be formed during e.g. hydraulic fracturing is thus crucial to better predict the outcome of a hydraulic fracturing job. For this, knowledge of the rock properties is crucial. The brittleness index is often used as a rock property that can be used to predict the fracturing behaviour of a rock for e.g. hydraulic fracturing of shales. Various terminologies of the brittleness index (BI1, BI2 and BI3) exist based on mineralogy, elastic constants and stress-strain behaviour (Jin et al., 2014, Jarvie et al., 2007 and Holt et al., 2011). A maximum brittleness index of 1 predicts very good and efficient fracturing behaviour while a minimum brittleness index of 0 predicts a much more ductile shale behaviour. Here, we have performed systematic petrophysical, acoustic and geomechanical analyses on a set of shale samples from Whitby (UK) and we have determined the three different brittleness indices on each sample by performing all the analyses on each of the samples. We show that each of the three brittleness indices are very different for the same sample and as such it can be concluded that the brittleness index is not a good predictor of the fracturing behaviour of shales. The brittleness index based on the acoustic data (BI1) all lie around values of 0.5, while the brittleness index based on the stress strain data (BI2) give an average brittleness index around 0.75, whereas the mineralogy brittleness index (BI3) predict values below 0.2. This shows that by using different estimates of the brittleness index different decisions can be made for hydraulic fracturing. If we would rely on the mineralogy (BI3), the Whitby mudstone is not a suitable

  11. Grain Boundary Segregation and Intergranular Fracture in Molybdenum

    Science.gov (United States)

    Kumar, A.; Eyre, B. L.

    1980-04-01

    The refractory group VIA metals generally exhibit intergranular brittleness when they are in the recrystallized condition. This causes severe problems in their fabrication and places major limitations on their practical application. The phenomenon, generally referred to as recrystallization embrittlement, results in large increases in the ductile-to-brittle transition temperature and a change in fracture mode in the lower shelf regime from cleavage to intergranular with a significant decrease in ductility. The embrittlement is widely considered to be associated with interstitial impurities but there have been few systematic studies to elucidate their effects. The present paper reports results from a systematic study of segregation and intergranular embrittlement in binary molybdenum-oxygen and ternary molybdenum-oxygen-carbon alloys. The experiments were carried out on 'bamboo' specimens containing a series of identical single grain boundaries traversing their cross-sections. Measurements have been made of the activation energy for oxygen segregation to grain boundaries in the binary molybdenum-oxygen alloys. The influence of carbon additions on the level of oxygen segregation has also been determined. In addition, the influence of oxygen segregation on the energy to fracture has been studied and this has involved quantitative measurements of the work of fracture and the contribution made by plastic deformation. Results from metallographic studies are also presented, showing the effects of segregation on fracture surface topography and dislocation structures immediately adjacent to the fracture surfaces. In discussing the results we consider the thermodynamics of oxygen segregation to grain boundaries and the role played by carbon in inhibiting segregation. It is proposed that carbon either increases the effective solubility of oxygen in molybdenum or acts as a trap for oxygen atoms. In either case the effect is to reduce the driving force for segregation. We also

  12. Thick-target yields of radioactive targets deduced from inverse kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Aikawa, M., E-mail: aikawa@sci.hokudai.ac.jp [Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan); Ebata, S.; Imai, S. [Meme Media Laboratory, Hokkaido University, Sapporo 060-8628 (Japan)

    2015-06-15

    The thick-target yield (TTY) is a macroscopic quantity reflected by nuclear reactions and matter properties of targets. In order to evaluate TTYs on radioactive targets, we suggest a conversion method from inverse kinematics corresponding to the reaction of radioactive beams on stable targets. The method to deduce the TTY is theoretically derived from inverse kinematics. We apply the method to the {sup nat}Cu({sup 12}C,X){sup 24}Na reaction to confirm availability. In addition, it is applied to the {sup 137}Cs + {sup 12}C reaction as an example of a radioactive system and discussed a conversion coefficient of a TTY measurement.

  13. Intrinsic neutrino properties: As deduced from cosmology, astrophysics, accelerator and non-accelerator experiments

    International Nuclear Information System (INIS)

    Rosen, S.P.

    1990-01-01

    I review the intrinsic properties of neutrinos as deduced from cosmological, astrophysical, and laboratory experiments. Bounds on magnetic moments and theoretical models which yield large moments but small masses are briefly discussed. The MSW solution to the solar neutrino problem is reviewed in light of the existing data from the 37 Cl and Kamiokande II experiments. The combined data disfavor the adiabatic solution and tend to support either the large angle solution or the nonadiabatic one. In the former case the 71 Ga signal will be suppressed by the same factor as for 37 Cl, and in the latter case the suppression factor could be as large as 10 or more. 41 refs

  14. Dotaciones para la recuperación de activos revertibles como deducibles del impuesto sobre sociedades

    OpenAIRE

    Duplá Marín, María José

    2001-01-01

    El objetivo final que nos propusimos con este trabajo de investigación fue profundizar en el estudio jurídico-tributario de las dotaciones al fondo de reversión como gasto deducible para determinar la base imponible del impuesto sobre sociedades, en aquellas sociedades concesionarias de servicios públicos con cláusula de reversión de activos, partiendo de su realidad contable.En consecuencia el trabajo se ciñe al estudio crítico de la regulación jurídica del fondo de reversión como gasto fisc...

  15. SignalP 4.0 Server - prediction results The deduced signal peptide ...

    Indian Academy of Sciences (India)

    15136770661wry

    SignalP 4.0 Server - prediction results. The deduced signal peptide data of MaSox4. Measure Position Value. Cutoff signal peptide? max. C. 40. 0.125 max. Y. 40. 0.111 max. S. 39. 0.117 mean S. 1-39. 0.097. D. 1-39. 0.103 0.450 NO. Name=Sequence SP='NO' D=0.103 D-cutoff=0.450 Networks=SignalP-noTM. Name= ...

  16. Fracture toughness of wet and dry particulate materials comprised of colloidal sized particles: role of plastic deformation.

    Science.gov (United States)

    Sesso, Mitchell L; Franks, George V

    2017-07-21

    This work demonstrates a method of measuring the fracture toughness of particulate materials comprised of colloidal sized particles over a wide range of saturation. Diametral compression of cylinders containing flaws of controlled length was used to measure the mode I fracture toughness. The effect of degree of saturation on the fracture toughness of slip cast ceramic grade alumina (d 50 = 0.7 μm) was investigated. Dry powder compacts have significantly lower fracture toughness than when the powder compact is nearly fully saturated. All observations are consistent with the fracture mechanism being predominantly brittle for the dry samples but predominantly ductile in the nearly saturated samples. The additional dissipation that occurs during the ductile fracture of the nearly saturated samples is due to plastic deformation in front of the crack tip. This well-known mechanism for toughening in metals has been quantified for the first time in soft matter. Analysis of the results indicates that the size of the plastic dissipation zone is more than an order of magnitude larger in the nearly saturated materials compared to the dry material. Understanding the fracture mechanisms that control the propagation of cracks through saturated, partially saturated and dry particulate materials comprised of colloidal sized particles provides additional insight into understanding drying cracks in paint, other coatings, ceramics and water treatment sludge.

  17. Hydraulic fracturing in shales: the spark that created an oil and gas boom

    Science.gov (United States)

    Olson, J. E.

    2017-12-01

    In the oil and gas business, one of the valued properties of a shale was its lack of flow capacity (its sealing integrity) and its propensity to provide mechanical barriers to hydraulic fracture height growth when exploiting oil and gas bearing sandstones. The other important property was the high organic content that made shale a potential source rock for oil and gas, commodities which migrated elsewhere to be produced. Technological advancements in horizontal drilling and hydraulic fracturing have turned this perspective on its head, making shale (or other ultra-low permeability rocks that are described with this catch-all term) the most prized reservoir rock in US onshore operations. Field and laboratory results have changed our view of how hydraulic fracturing works, suggesting heterogeneities like bedding planes and natural fractures can cause significant complexity in hydraulic fracture growth, resulting in induced networks of fractures whose details are controlled by factors including in situ stress contrasts, ductility contrasts in the stratigraphy, the orientation and strength of pre-existing natural fractures, injection fluid viscosity, perforation cluster spacing and effective mechanical layer thickness. The stress shadowing and stress relief concepts that structural geologists have long used to explain joint spacing and orthogonal fracture pattern development in stratified sequences are key to understanding optimal injection point spacing and promotion of more uniform length development in induced hydraulic fractures. Also, fracture interaction criterion to interpret abutting vs crossing natural fracture relationships in natural fracture systems are key to modeling hydraulic fracture propagation within natural fractured reservoirs such as shale. Scaled physical experiments provide constraints on models where the physics is uncertain. Numerous interesting technical questions remain to be answered, and the field is particularly appealing in that better

  18. Extended drop testing with precracked DCI-casks and evaluations on safety against brittle fracture

    International Nuclear Information System (INIS)

    Wieser, K.E.; Frenz, H.; Gogolin, B.

    1993-01-01

    This paper is a summary of a research study as part of comparable efforts in Japan, France and the USA aimed at developing principles, procedures and material data for the brittle fracture safe design of thickwalled shipping containers made from ductile cast iron (DCI) and other material susceptible - in principle - to nonductile failure. Furthermore, the application of fracture mechanics was to be qualified as an alternative method, relative to the experimental approach applied in previous licensing procedures in Germany and to be demonstrated by subjecting a full-size precracked prototype to drop tests. (J.P.N.)

  19. Effect of Temperature on the Fracture Toughness of Hot Isostatically Pressed 304L Stainless Steel

    Science.gov (United States)

    Cooper, A. J.; Brayshaw, W. J.; Sherry, A. H.

    2018-03-01

    Herein, we have performed J- Resistance multi-specimen fracture toughness testing of hot isostatically pressed (HIP'd) and forged 304L austenitic stainless steel, tested at elevated (300 °C) and cryogenic (- 140 °C) temperatures. The work highlights that although both materials fail in a pure ductile fashion, stainless steel manufactured by HIP displays a marked reduction in fracture toughness, defined using J 0.2BL, when compared to equivalently graded forged 304L, which is relatively constant across the tested temperature range.

  20. Microstructure, mechanical behaviour and fracture of pure tungsten wire after different heat treatments

    DEFF Research Database (Denmark)

    Zhao, P.; Riesch, J.; Höschen, T.

    2017-01-01

    treatments in terms of microstructure, mechanical behaviour and fracture mode. Recrystallization is already observed at a relatively low temperature of 1273 K due to the large driving force caused by a high dislocation density. Annealing for 30 min at 1900 K also leads to recrystallization, but causes......-edge-necking of individual grains on the fracture surface. While the wire recrystallized at 1900 K displays large, almost equiaxed grains with low aspect ratios as well as distinct brittle properties. Therefore, it is suggested that a high aspect ratio of the grains is important for the ductile behaviour of tungsten wire...

  1. Fractures in multiple sclerosis

    DEFF Research Database (Denmark)

    Stenager, E; Jensen, K

    1991-01-01

    In a cross-sectional study of 299 MS patients 22 have had fractures and of these 17 after onset of MS. The fractures most frequently involved the femoral neck and trochanter (41%). Three patients had had more than one fracture. Only 1 patient had osteoporosis. The percentage of fractures increase...

  2. Assessment of fracture risk

    International Nuclear Information System (INIS)

    Kanis, John A.; Johansson, Helena; Oden, Anders; McCloskey, Eugene V.

    2009-01-01

    Fractures are a common complication of osteoporosis. Although osteoporosis is defined by bone mineral density at the femoral neck, other sites and validated techniques can be used for fracture prediction. Several clinical risk factors contribute to fracture risk independently of BMD. These include age, prior fragility fracture, smoking, excess alcohol, family history of hip fracture, rheumatoid arthritis and the use of oral glucocorticoids. These risk factors in conjunction with BMD can be integrated to provide estimates of fracture probability using the FRAX tool. Fracture probability rather than BMD alone can be used to fashion strategies for the assessment and treatment of osteoporosis.

  3. Assessment of fracture risk

    Energy Technology Data Exchange (ETDEWEB)

    Kanis, John A. [WHO Collaborating Centre for Metabolic Bone Diseases, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX (United Kingdom)], E-mail: w.j.pontefract@sheffield.ac.uk; Johansson, Helena; Oden, Anders [WHO Collaborating Centre for Metabolic Bone Diseases, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX (United Kingdom); McCloskey, Eugene V. [WHO Collaborating Centre for Metabolic Bone Diseases, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX (United Kingdom); Osteoporosis Centre, Northern General Hospital, Sheffield (United Kingdom)

    2009-09-15

    Fractures are a common complication of osteoporosis. Although osteoporosis is defined by bone mineral density at the femoral neck, other sites and validated techniques can be used for fracture prediction. Several clinical risk factors contribute to fracture risk independently of BMD. These include age, prior fragility fracture, smoking, excess alcohol, family history of hip fracture, rheumatoid arthritis and the use of oral glucocorticoids. These risk factors in conjunction with BMD can be integrated to provide estimates of fracture probability using the FRAX tool. Fracture probability rather than BMD alone can be used to fashion strategies for the assessment and treatment of osteoporosis.

  4. Ductility improvement by twinning and twin–slip interaction in a Mg-Y alloy

    International Nuclear Information System (INIS)

    Zhou, Na; Zhang, Zhenyan; Jin, Li; Dong, Jie; Chen, Bin; Ding, Wenjiang

    2014-01-01

    Highlights: • A high elongation of ∼33% was achieved for magnesium alloy through common extrusion. • Basal slip and extension twinning are the dominant deformation modes for the high ductility. • Non-basal slip, contraction twinning and twin-slip interaction also contribute to the ductility. - Abstract: An extruded Mg-3.0Y alloy with non-basal texture of 〈42 ¯ 2 ¯ 3〉 component was fabricated by common extrusion and exhibited a high elongation of ∼33%. The deformation modes and microstructure evolution of the extruded Mg-3.0Y alloy during the tensile test at room temperature were investigated to explore the reasons for the high ductility by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). The results suggested that texture changed from 〈42 ¯ 2 ¯ 3〉 to 〈101 ¯ 0〉 component during the tensile deformation, which is attributed the slip and twinning activity. Basal slip and extension twinning are the dominant deformation modes for the high ductility. Meanwhile, the activation of non-basal slip, contraction twinning and twin–slip interaction also contributes to the good ductility of Mg-3.0Y alloy

  5. Kinetic Ductility and Force-Spike Resistance of Proteins from Single-Molecule Force Spectroscopy.

    Science.gov (United States)

    Cossio, Pilar; Hummer, Gerhard; Szabo, Attila

    2016-08-23

    Ductile materials can absorb spikes in mechanical force, whereas brittle ones fail catastrophically. Here we develop a theory to quantify the kinetic ductility of single molecules from force spectroscopy experiments, relating force-spike resistance to the differential responses of the intact protein and the unfolding transition state to an applied mechanical force. We introduce a class of unistable one-dimensional potential surfaces that encompass previous models as special cases and continuously cover the entire range from ductile to brittle. Compact analytic expressions for force-dependent rates and rupture-force distributions allow us to analyze force-clamp and force-ramp pulling experiments. We find that the force-transmitting protein domains of filamin and titin are kinetically ductile when pulled from their two termini, making them resistant to force spikes. For the mechanostable muscle protein titin, a highly ductile model reconciles data over 10 orders of magnitude in force loading rate from experiment and simulation. Copyright © 2016 Biophysical Society. All rights reserved.

  6. Ductility Of fly ash - slag based reinforced geopolymer concrete elements cured at room temperature.

    Directory of Open Access Journals (Sweden)

    Mahantesh N.B.

    2017-01-01

    Full Text Available Ductility of the flexural element is the main governing property for healthy performance of structural element. Although numerous factors contribute towards the ductility of Reinforced Geopolymer Concrete (RGPC elements, low calcium based fly ash and GGBS have chemical proportions which make RGPC develop significant ductility along with steel reinforcement – when mixed in an intelligent way satisfying structural and economic conditions. In the present research work influence of low calcium fly ash, GGBS, River sand, M-sand, Steel Grade, manufactured fibres and natural fibres are used to study the ductile behaviour of RGPC sections by load testing 51 under reinforced flexural elements. The study reveals that fly ash - slag based reinforced flexural elements behave in line with OPC based RCC elements. The provisions mentioned in Indian RC designer IS:456-2000 can be used to predict the flexural behaviour of reinforced geopolymer concrete elements. The average flexural ductility of these test specimens observed to lie in between 2 & 3.

  7. Identifying osteoporotic vertebral fracture

    Science.gov (United States)

    2015-01-01

    Osteoporosis per se is not a harmful disease. It is the sequela of osteoporosis and most particularly the occurrence of osteoporotic fracture that makes osteoporosis a serious medical condition. All of the preventative measures, investigations, treatment and research into osteoporosis have one primary goal and that is to prevent the occurrence of osteoporotic fracture. Vertebral fracture is by far and away the most prevalent osteoporotic fracture. The significance and diagnosis of vertebral fracture are discussed in this article. PMID:26435923

  8. Plasticity, Fracture and Friction in Steady-State Plate Cutting

    DEFF Research Database (Denmark)

    Simonsen, Bo Cerup; Wierzbicki, Tomasz

    1997-01-01

    A closed form solution to the problem of steady-state wedge cutting through a ductile metal plate is presented. The considered problem is an idealization of a ship bottom raking process, i.e. a continuous cutting damage of a ship bottom by a hard knife-like rock in a grounding event. A new...... extension of the presented plate model to include more structural members as for example the stiffeners attached to a ship bottom plating. The fracture process is discussed and the model is formulated partly on the basis of the material fracture toughness. The effect of friction and the reaction force...... perpendicular to the direction of motion is derived theoretically in a consistent manner. The perpendicular reaction force is of paramount importance for prediction the structural damage of a ship hull because it governs the vertical ship motion and rock penetration which is strongly coupled with the horizontal...

  9. Thin wall ductile iron casting as a substitute for aluminum alloy casting in automotive industry

    Directory of Open Access Journals (Sweden)

    M. Górny

    2009-01-01

    Full Text Available In paper it is presented thin wall ductile iron casting (TWDI as a substitute of aluminium alloy casting. Upper control arm made of ductile iron with wall thickness ranging from 2 – 3.7 mm was produced by inmold process. Structure, mechanical properties and computer simulations were investigated. Structural analysis of TWDI shows pearlitic-ferritic matrix free from chills and porosity. Mechanical testing disclose superior ultimate tensile strength (Rm, yield strength (Rp0,2 and slightly lower elongation (E of TWDI in comparison with forged control arm made of aluminium alloy (6061-T6. Moreover results of computer simulation of static loading for tested control arms are presented. Analysis show that the light-weight ductile iron casting can be loaded to similar working conditions as the forged Al alloy without any potential failures.

  10. Alloy-dependent deformation behavior of highly ductile nanocrystalline AuCu thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lohmiller, Jochen [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany); Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); Spolenak, Ralph [Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); Gruber, Patric A., E-mail: patric.gruber@kit.edu [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany)

    2014-02-10

    Nanocrystalline thin films on compliant substrates become increasingly important for the development of flexible electronic devices. In this study, nanocrystalline AuCu thin films on polyimide substrate were tested in tension while using a synchrotron-based in situ testing technique. Analysis of X-ray diffraction profiles allowed identifying the underlying deformation mechanisms. Initially, elastic and microplastic deformation is observed, followed by dislocation-mediated shear band formation, and eventually macroscopic crack formation. Particularly the influence of alloy composition, heat-treatment, and test temperature were investigated. Generally, a highly ductile behavior is observed. However, high Cu concentrations, annealing, and/or large plastic strains lead to localized deformation and hence reduced ductility. On the other hand, enhanced test temperature allows for a delocalized deformation and extended ductility.

  11. Structural analysis of a fractured basement reservoir, central Yemen

    Science.gov (United States)

    Veeningen, Resi; Rice, Hugh; Schneider, Dave; Grasemann, Bernhard; Decker, Kurt

    2013-04-01

    The Pan-African Arabian-Nubian Shield (ANS), within which Yemen lies, formed as a result of Neoproterozoic collisional events between c. 870-550 Ma. Several subsequent phases of extension occurred, from the Mesozoic (due to the breakup of Gondwana) to the Recent (forming the Gulf of Aden and the Red Sea). These resulted in the formation of numerous horst- and-graben structures and the development of fractured basement reservoirs in the southeast part of the ANS. Two drill cores from the Mesozoic Marib-Shabwa Basin, central Yemen, penetrated the upper part of the Pan-African basement. The cores show both a lithological and structural inhomogeneity, with variations in extension-related deformation structures such as dilatational breccias, open fractures and closed veins. At least three deformation events have been recognized: D1) Ductile to brittle NW-SE directed faulting during cooling of a granitic pluton. U-Pb zircon ages revealed an upper age limit for granite emplacement at 627±3.5 Ma. As these structures show evidence for ductile deformation, this event must have occurred during the Ediacaran, shortly after intrusion, since Rb/Sr and (U-Th)/He analyses show that subsequent re-heating of the basement did not take place. D2) The development of shallow dipping, NNE-SSW striking extensional faults that formed during the Upper Jurassic, simultaneously with the formation of the Marib-Shabwa Basin. These fractures are regularly cross-cut by D3. D3) Steeply dipping NNE-SSW to ENE-WSW veins that are consistent with the orientation of the opening of the Gulf of Aden. These faults are the youngest structures recognized. The formation of ductile to brittle faults in the granite (D1) resulted in a hydrothermally altered zone ca. 30 cm wide replacing (mainly) plagioclase with predominantly chlorite, as well as kaolinite and heavy element minerals such as pyrite. The alteration- induced porosity has an average value of 20%, indicating that the altered zone is potentially a

  12. Ductility Enhancement of Molybdenum Phase by Nano-sizedd Oxide Dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Bruce Kang

    2008-07-31

    The present research is focused on ductility enhancement of molybdenum (Mo) alloys by adding nano-sized oxide particles to the alloy system. The research approach includes: (1) determination of microscopic mechanisms responsible for the macroscopic ductility enhancement effects through atomistic modeling of the metal-ceramic interface; (2) subsequent computer simulation-aided optimization of composition and nanoparticle size of the dispersion for improved performance; (3) synthesis and characterization of nanoparticle dispersion following the guidance from atomistic computational modeling analyses (e.g., by processing a small sample of Mo alloy for evaluation); and (4) experimental testing of the mechanical properties to determine optimal ductility enhancement.Through atomistic modeling and electronic structure analysis using full-potential linearized muffin-tin orbital (FP-LMTO) techniques, research to date has been performed on a number of selected chromium (Cr) systems containing nitrogen (N) and/or magnesium oxide (MgO) impurities. The emphasis has been on determining the properties of the valence electrons and the characteristics of the chemical bonds they formed. It was found that the brittle/ductile behavior of this transitional metal system is controlled by the relative population of valence charges: bonds formed by s valence electrons yield metallic, ductile behavior, whereas bonds formed by d valence electrons lead to covalent, brittle behavior. The presence of valence bands from impurities also affects the metal bonding, thereby explaining the detrimental and beneficial effects induced by the inclusion of N impurities and MgO dispersions. These understandings are useful for optimizing ductility enhancement effects on the dispersion materials.

  13. Imaging of vertebral fractures

    Directory of Open Access Journals (Sweden)

    Ananya Panda

    2014-01-01

    Full Text Available Vertebral fracture is a common clinical problem. Osteoporosis is the leading cause of non-traumatic vertebral fracture. Often, vertebral fractures are not clinically suspected due to nonspecific presentation and are overlooked during routine interpretation of radiologic investigations. Moreover, once detected, many a times the radiologist fails to convey to the clinician in a meaningful way. Hence, vertebral fractures are a constant cause of morbidity and mortality. Presence of vertebral fracture increases the chance of fracture in another vertebra and also increases the risk of subsequent hip fracture. Early detection can lead to immediate therapeutic intervention improving further the quality of life. So, in this review, we wish to present a comprehensive overview of vertebral fracture imaging along with an algorithm of evaluation of vertebral fractures.

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

    Directory of Open Access Journals (Sweden)

    Myszka D.

    2013-03-01

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

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

    Directory of Open Access Journals (Sweden)

    S. Savićević

    2017-01-01

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

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

    Directory of Open Access Journals (Sweden)

    D. Myszka

    2013-01-01

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

  17. Influence of the section size and holding time on the graphite parameters of ductile iron production

    Directory of Open Access Journals (Sweden)

    S. Bockus

    2009-01-01

    Full Text Available This work was conducted to establish the conditions required to produce a desirable structure of the castings of various section sizes. This investigation was focused on the study of the influence of cooling rate or section size and holding time on graphite parameters of the ductile iron. Plates having thickness between 3 and 50mm were cast in sand molds using the same melt. The present investigation has shown that the section size of ductile iron castings and holding time had strong effect on the graphite parameters of the castings.

  18. Investigation of solidification of thin walled ductile cast iron using temperature measurement

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels

    2005-01-01

    Investigation of solidification of thin walled ductile cast iron can be improved using temperature measurement. This article includes some background of the precautions that have to be taken when measuring temperatures in thin walled castings. The aim is to minimize influence of temperature...... measurement on castings and to get sufficient response time of thermocouples. Investigation of thin wall ductile iron has been performed with temperature measurement in plates with thickness between 2,8 and 8mm. The cooling curves achieved are combined with examination of the microstructure in order to reveal...

  19. Examination and Elimination of Defects in Cone Casting Made of Ductile Cast Iron

    Directory of Open Access Journals (Sweden)

    Guzik E.

    2013-12-01

    Full Text Available In the scope of existing cooperation with the Foundry of Cast Iron ZM “WSK Rzeszów” Ltd. there was carried out research work of microstructure and mechanical properties in the walls of a cone casting made of ductile cast iron. The particular attention was being put to the search of the potential brittle phases which have deleterious effect on ductility and dynamic properties of highly strained use of the casting prone to the potential risk of cracks during the highly strained use.

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

    Directory of Open Access Journals (Sweden)

    Amir Sadighzadeh Benam

    2015-01-01

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

  1. Characteristics of ADI Ductile Cast Iron with Single Addition of 1.56% Ni

    Directory of Open Access Journals (Sweden)

    Mrzygłód B.

    2017-12-01

    Full Text Available The results of examinations of microstructure and an analysis of its impact on selected mechanical properties of austempered ductile iron (ADI were presented in the paper. The ADI was produced from the ductile iron containing 1.56% Ni only alloying addition. The effect of the austempering time and temperature on the microstructure and mechanical properties of the examined cast iron was considered. Constant conditions of austenitizing were assumed and six variants of the austempering treatment were adopted. The studyof mechanical properties included a static tensile test, Charpy impact strength test and Brinellhardness measurement.

  2. Investigation on local ductility of 6xxx-aluminium sheet alloys

    Science.gov (United States)

    Henn, P.; Liewald, M.; Sindel, M.

    2017-09-01

    Within the scope of this paper influence of localization of loading conditions on the ductility of two different 6xxx-aluminium sheet alloys is investigated. In order to improve the prediction of sheet material crash performance, material parameters based on uniaxial tensile and notched tensile tests are determined with varying consolidation areas. Especially evaluation methods based on the localized necking behaviour in tensile tests are investigated. The potential of local ductility characterisation is validated with results of Edge-Compression Tests (ECT) which applies load conditions that occur in actual crash events.

  3. Assessment of ductile iron casting process with the use of the DRSA method

    Directory of Open Access Journals (Sweden)

    Kujawińska A.

    2016-01-01

    Full Text Available The paper introduces a concept of assessment of a ductile iron casting process with use of the rule-based approach, known as DRSA (dominance-based rough set approach. The research was conducted in a large Polish foundry. The collected data concern the chemical composition and mechanical properties of the used ductile cast iron. In the paper, a methodology of creating a rule-based moulding model for the tensile strength was proposed. The quality, sensitivity and accuracy of the model extracted from the data were examined. The studies proved its usefulness in the industrial practice and for aiding of the decision making process.

  4. Studies of void growth in a thin ductile layer between ceramics

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    1997-01-01

    growth by a ductile mechanism along the thin layer. Plastic flow in the layer is highly constrained by the ceramics, so that a high. level of triaxial tension develops, leading in some cases to cavitation instabilities. The computations are continued to a state near the occurrence of void coalescence.......The growth of voids in a thin ductile layer between ceramics is analysed numerically, using an axisymmetric cell model to represent an array of uniformly distributed spherical voids at the central plane of the layer. The purpose is to determine the full traction-separation law relevant to crack...

  5. Room temperature tensile ductility in polycrystalline B2 Ni-30Al-20Fe

    Science.gov (United States)

    Guha, Sumit; Munroe, Paul; Baker, Ian

    1989-01-01

    A room-temperature tensile elongation of about 2.5 percent, where the only slip vector observed was the 100, has been determined for a double-extruded B2 Ni-30Al-20Fe alloy consisting of recrystallized equiaxed grains about 25 microns in diameter; these results suggest that 100-slip does not preclude limited ductility in polycrystalline B2 alloys in tension at low temperatures. A suppression of ordering through resort to rapid solidification, in other words, is not necessary for ductility, since the cast and as-extruded alloy presently examined is ordered.

  6. Enhancing the Ductility of Laser-Welded Copper-Aluminum Connections by using Adapted Filler Materials

    Science.gov (United States)

    Weigl, M.; Albert, F.; Schmidt, M.

    Laser micro welding of direct copper-aluminum connections typically leads to the formation of intermetallic phases and an embrittlement of the metal joints. By means of adapted filler materials it is possible to reduce the brittle phases and thereby enhance the ductility of these dissimilar connections. As the element silicon features quite a well compatibility with copper and aluminum, filler materials based on Al-Si and Cu-Si alloys are used in the current research studies. In contrast to direct Cu-Al welds, the aluminum filler alloy AlSi12 effectuates a more uniform element mixture and a significantly enhanced ductility.

  7. High strength and utilizable ductility of bulk ultrafine-grained Cu-Al alloys

    Science.gov (United States)

    An, X. H.; Han, W. Z.; Huang, C. X.; Zhang, P.; Yang, G.; Wu, S. D.; Zhang, Z. F.

    2008-05-01

    Lack of plasticity is the main drawback for nearly all ultrafine-grained (UFG) materials, which restricts their practical applications. Bulk UFG Cu-Al alloys have been fabricated by using equal channel angular pressing technique. Its ductility was improved to exceed the criteria for structural utility while maintaining a high strength by designing the microstructure via alloying. Factors resulting in the simultaneously enhanced strength and ductility of UFG Cu-Al alloys are the formation of deformation twins and their extensive intersections facilitating accumulation of dislocations.

  8. Behaviour of the Pleistocene marsupial lion deduced from claw marks in a southwestern Australian cave.

    Science.gov (United States)

    Arman, Samuel D; Prideaux, Gavin J

    2016-02-15

    The marsupial lion, Thylacoleo carnifex, was the largest-ever marsupial carnivore, and is one of the most iconic extinct Australian vertebrates. With a highly-specialised dentition, powerful forelimbs and a robust build, its overall morphology is not approached by any other mammal. However, despite >150 years of attention, fundamental aspects of its biology remain unresolved. Here we analyse an assemblage of claw marks preserved on surfaces in a cave and deduce that they were generated by marsupial lions. The distribution and skewed size range of claw marks within the cave elucidate two key aspects of marsupial lion biology: they were excellent climbers and reared young in caves. Scrutiny of >10,000 co-located Pleistocene bones reveals few if any marsupial lion tooth marks, which dovetails with the morphology-based interpretation of the species as a flesh specialist.

  9. Vortex magnetic structure in circularly magnetized microwires as deduced from magneto-optical Kerr measurements

    KAUST Repository

    Ivanov, Yurii P.

    2014-02-14

    The magneto-optic Kerr effect has been employed to determine the magnetization process and estimate the domain structure of microwires with circular magnetic anisotropy. The diameter of microwires was 8 μm, and pieces 2 cm long were selected for measurements. The analysis of the local surface longitudinal and transverse hysteresis loops has allowed us to deduce a vortex magnetic structure with axial core and circular external shell. Moreover, a bamboo-like surface domain structure is confirmed with wave length of around 10 to 15 μm and alternating chirality in adjacent circular domains. The width of the domain wall is estimated to be less than 3 μm. Finally, closure domain structures with significant helical magnetization component are observed extending up to around 1000 μm from the end of the microwire.

  10. Thoracic impedance change equation deduced on the basis of parallel impedance model and Ohm's law.

    Science.gov (United States)

    Qiu-Jin, Xiao; Zhen, Wang; Ming-Xing, Kuang; Ping, Wen; Pei, Liu; Jian-Feng, Ji

    2012-02-01

    The aim of the present study is to investigate an impedance change equation suited with the measurement of the impedance cardiograph (ICG). Based on a parallel impedance model and Ohm's law, an impedance change equation differed from Nyboer's equation is deduced. It is verified with the experiments of the impedance cardiography in 100 healthy adults. This equation shows that the thoracic impedance change (ΔZ) is directly proportional to the value of the volume change (ΔV) of the blood vessel, to the ratio of the basic impedance to the body height (Z(0)/H), while it is inversely proportional to the square of the chest circumference (C(t) (2)). These are supported by the experimental results in the measurement of the ICG. The equation proposed in the present paper is coincident with the actual condition in the measurement of the ICG.

  11. Effect of Normalizing Temperature on Fracture Characteristic of Tensile and Impact Tested Creep Strength-Enhanced Ferritic P92 Steel

    Science.gov (United States)

    Saini, N.; Pandey, C.; Mahapatra, M. M.

    2017-11-01

    The high-temperature Cr-Mo creep strength-enhanced ferritic (CSEF) steels are mainly used in nuclear and thermal power plants. In the present investigation, a systematic study on fracture surface morphologies of tensile and impact tested specimens and mechanical properties of cast and forged (C&F) P92 steel was performed for various heat treatment conditions. The heat treatment was carried out in normalizing temperature range of 950-1150 °C and then tempered to a fixed tempering temperature of 760 °C. The effect of varying normalizing temperatures before and after tempering on microstructure evolution, tensile properties, Vicker's hardness and Charpy toughness was studied. The normalizing temperature before and after tempering was having a noticeable effect on mechanical properties of as-received P92 steel. The fracture surface of impact and tensile tested samples was also studied for various normalizing temperatures with or without tempering. Fracture surface morphology was affected by the presence of secondary phase carbide particles. The fraction area of cleavage facets on the tensile fracture surface was found to be increased with an increase in the normalizing temperature. The fractured tensile specimens were characterized by transgranular ductile dimples, tear ridges and transgranular cleavage facets for various heat treatments. The fracture mode of impact tested samples was more complex. It showed both quasi-cleavage facets and ductile dimple tearing for various normalizing temperatures.

  12. Time to failure of hierarchical load-transfer models of fracture

    DEFF Research Database (Denmark)

    Vázquez-Prada, M; Gómez, J B; Moreno, Y

    1999-01-01

    The time to failure, T, of dynamical models of fracture for a hierarchical load-transfer geometry is studied. Using a probabilistic strategy and juxtaposing hierarchical structures of height n, we devise an exact method to compute T, for structures of height n+1. Bounding T, for large n, we are a...... are able to deduce that the time to failure tends to a nonzero value when n tends to infinity. This numerical conclusion is deduced for both power law and exponential breakdown rules....

  13. Development and Testing of a Linear Polarization Resistance Corrosion Rate Probe for Ductile Iron Pipe (Web Report 4361)

    Science.gov (United States)

    The North American water and wastewater community has hundreds of millions of feet of ductile iron pipe in service. Only a portion of the inventory has any form of external corrosion control. Ductile iron pipe, in certain environments, is subject to external corrosion.Linear Pola...

  14. A systematic concept of assuring structural integrity of components and parts for applying to highly ductile materials through brittle material

    International Nuclear Information System (INIS)

    Suzuki, Kazuhiko

    2007-09-01

    Concepts of assuring structural integrity of plant components have been developed under limited conditions of either highly ductile or brittle materials. There are some cases where operation in more and more severe conditions causes a significant reduction in ductility for materials with a high ductility before service. Use of high strength steels with relatively reduced ductility is increasing as industry applications. Current concepts of structural integrity assurance under the limited conditions of material properties or on the requirement of no significant changes in material properties even after long service will fail to incorporate expected technological innovations. A systematic concept of assuring the structural integrity should be developed for applying to highly ductile materials through brittle materials. Objectives of the on-going research are to propose a detail of the systematic concept by considering how we can develop the concept without restricting materials and for systematic considerations on a broad range of material properties from highly ductile materials through brittle materials. First, background of concepts of existing structural codes for components of highly ductile materials or for structural parts of brittle materials are discussed. Next, issues of existing code for parts of brittle materials are identified, and then resolutions to the issues are proposed. Based on the above-mentioned discussions and proposals, a systematic concept is proposed for application to components with reduced ductility materials and for applying to components of materials with significantly changing material properties due to long service. (author)

  15. Fracture Mapping with Laser Scan Technology and Discrete Fracture Network Modeling to Support Groundwater Recharge Estimates

    Science.gov (United States)

    Voeckler, H. M.; Allen, D.; Forster, C.; Sturzenegger, M.

    2006-12-01

    A Discrete Fracture Network (DFN) approach is used to estimate the hydraulic properties of fractured, low- permeability bedrock in order to assess the spatial variability of recharge for an experimental watershed in mountainous terrain of the Okanagan Valley in central British Columbia. Fracture mapping was undertaken at 30 outcrop locations using traditional scan line mapping techniques. Most of the rocks in the study area belong to the geological unit of the Shuswap Complex, a Proterozoic to Paleozoic high grade metamorphic core complex, consisting of migmatitic gneisses and pegmatites. Further east in the study area, the Okanagan Batholith is predominant, a Paleocene to Early Eocene leucogranite. The fractured aquifer appears to be associated with the 290-km long Okanagan Valley Fault Zone (OVFZ), a north-south striking ductile shear zone with a superimposed, west-dipping, low-angle detachment fault. The study area is located in the footwall of the fault about 500m east of its main trace. Our goal is to assess how spatial variations in fracture network porosity and permeability may be related to the OVFZ. Shallow dipping fractures that have the greatest persistence and apparent aperture are mostly oriented sub-parallel to the low-angle detachment fault. Near vertical fractures have higher intensity, but lower persistence and smaller apparent apertures. Fracture statistical analysis, supported by FracMan® software, is combined with finite element flow simulations (using MAFIC®) to compute apparent permeability values parallel and perpendicular to the OKFZ. We expect the results of our analyses to show that the vertical fracture networks provide key pathways for groundwater to recharge the more prevalent low-angle fracture networks that comprise the main aquifer system. For two of those 30 outcrop locations, a 3D terrestrial laser scanner (ILRIS 3D) was used to map the fracture network across the rock face. At a rate of at least 1000 points/second, the laser

  16. Mechanical properties and fracture toughness of rail steels and thermite welds at low temperature

    Science.gov (United States)

    Wang, Yuan-qing; Zhou, Hui; Shi, Yong-jiu; Feng, Bao-rui

    2012-05-01

    Brittle fracture occurs frequently in rails and thermite welded joints, which intimidates the security and reliability of railway service. Railways in cold regions, such as Qinghai-Tibet Railway, make the problem of brittle fracture in rails even worse. A series of tests such as uniaxial tensile tests, Charpy impact tests, and three-point bending tests were carried out at low temperature to investigate the mechanical properties and fracture toughness of U71Mn and U75V rail steels and their thermite welds. Fracture micromechanisms were analyzed by scanning electron microscopy (SEM) on the fracture surfaces of the tested specimens. The ductility indices (percentage elongation after fracture and percentage reduction of area) and the toughness indices (Charpy impact energy A k and plane-strain fracture toughness K IC) of the two kinds of rail steels and the corresponding thermite welds all decrease as the temperature decreases. The thermite welds are more critical to fracture than the rail steel base metals, as indicated by a higher yield-to-ultimate ratio and a much lower Charpy impact energy. U71Mn rail steel is relatively higher in toughness than U75V, as demonstrated by larger A k and K IC values. Therefore, U71Mn rail steel and the corresponding thermite weld are recommended in railway construction and maintenance in cold regions.

  17. Fracture toughness in the transition region of a carbon steel and a ferritic nodular cast iron

    International Nuclear Information System (INIS)

    Nakano, Keishi; Yasunaka, Takashi

    1995-01-01

    In order to characterize the fracture toughness in the ductile-brittle transition region for thick-walled cylinders of ASME SA350 Gr.LF5 carbon steel and JIS FCD300LT ferritic nodular cast iron, elastic-plastic fracture toughness tests were carried out. The specimens were fatigue precracked compact tension (CT) specimens of 25mm in thickness. The tensile testing machines used were Instron type, electrohydraulic type and drop-weight type ones. In the static fracture toughness test on a FCD300LT cast iron, CT specimens were often fractured at somewhat higher loads after the initiation of pop-in cracks. Although the scatter of pop-in fracture toughness was small, the values of critical J-integral at the unstable brittle fracture scattered largely. In the transition region of SA350 steel, the initiation of pop-in crack was not observed, and fracture toughness scattered largely. At the propagation of the unstable crack near the transition temperature, the Weibull distribution provides good fits for the critical CTOD and the critical J-integral. This distribution can be mainly interpreted by the scatter of the distance between the precrack tip and the origin of unstable brittle fracture. (author)

  18. Acoustic emission analysis of crack resistance and fracture behavior of 20GL steel having the gradient microstructure and strength

    Science.gov (United States)

    Nikulin, S.; Nikitin, A.; Belov, V.; Rozhnov, A.; Turilina, V.; Anikeenko, V.; Khatkevich, V.

    2017-07-01

    The crack resistances as well as fracture behavior of 20GL steel quenched with a fast-moving water stream and having gradient microstructure and strength are analyzed. Crack resistance tests with quenched and normalized flat rectangular specimens having different cut lengths loaded by three-point bending with acoustic emission measurements have been performed. The critical J-integral has been used as the crack resistance parameter of the material. Quenching with a fast moving water stream leads to gradient (along a specimen wall thickness) strengthening of steel due to highly refined gradient microstructure formation of the troostomartensite type. Quenching with a fast-moving water stream increases crack resistance Jc , of 20GL steel by a factor of ∼ 1.5. The fracture accrues gradually with the load in the normalized specimens while the initiated crack is hindered in the variable ductility layer and further arrested in the more ductile core in the quenched specimens.

  19. Combined macroscopic and microscopic approach to the fracture of metals. Technical annual progress report, 1979-1980

    International Nuclear Information System (INIS)

    Asaro, R.J.; Gurland, J.; Needleman, A.; Rice, J.R.

    1980-06-01

    The following results are reported: (1) extremely good theoretical-experimental correlation was found between our theoretical predictions based on asymptotic analysis with numerical finite element studies and the experimentally monitored crack growth for a large range of stable crack growth in 4140 steel; (2) a theoretical model was developed for the critical conditions of crack initiation at rigid particles as a precursor of ductile rupture in steels; (3) as part of environmentally sensitive fracture mechanisms, it was found that hydrogen can promote a ductile-to-brittle fracture transition with increasing charging current density in low carbon steel; and (4) a new variational principle has been established for the combined processes of plastic creep flow and grain boundary diffusion and has been constructively applied to the problem of cavity growth under creep conditions

  20. Fractures (Broken Bones): First Aid

    Science.gov (United States)

    First aid Fractures (broken bones) Fractures (broken bones): First aid By Mayo Clinic Staff A fracture is a ... 10, 2018 Original article: http://www.mayoclinic.org/first-aid/first-aid-fractures/basics/ART-20056641 . Mayo Clinic ...