Experimental and Computational Study of Ductile Fracture in Small Punch Tests

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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.

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

Science.gov (United States)

Gülçimen Çakan, Betül; Soyarslan, Celal; Bargmann, Swantje; Hähner, Peter

2017-10-17

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.

Development of Nanostructured Austempered Ductile Cast Iron

Science.gov (United States)

Panneerselvam, Saranya

Austempered Ductile Cast Iron is emerging as an important engineering materials in recent years because of its excellent combination of mechanical properties such as high strength with good ductility, good fatigue strength and fracture toughness together with excellent wear resistance. These combinations of properties are achieved by the microstructure consisting of acicular ferrite and high carbon austenite. Refining of the ausferritic microstructure will further enhance the mechanical properties of ADI and the presence of proeutectoid ferrite in the microstructure will considerably improve the ductility of the material. Thus, the focus of this investigation was to develop nanostructured austempered ductile cast iron (ADI) consisting of proeutectoid ferrite, bainitic ferrite and high carbon austenite and to determine its microstructure-property relationships. Compact tension and cylindrical tensile test samples were prepared as per ASTM standards, subjected to various heat treatments and the mechanical tests including the tensile tests, plane strain fracture toughness tests, hardness tests were performed as per ASTM standards. Microstructures were characterized by optical metallography, X-ray diffraction, SEM and TEM. Nanostructured ADI was achieved by a unique heat treatment consisting of austenitization at a high temperature and subsequent plastic deformation at the same austenitizing temperature followed by austempering. The investigation also examined the effect of cryogenic treatment, effect of intercritical austenitizing followed by single and two step austempering, effect of high temperature plastic deformation on the microstructure and mechanical properties of the low alloyed ductile cast iron. The mechanical and thermal stability of the austenite was also investigated. An analytical model has been developed to understand the crack growth process associated with the stress induced transformation of retained austenite to martensite.

Investigation of hot ductility in Al-killed boron steels

International Nuclear Information System (INIS)

Chown, L.H.; Cornish, L.A.

2008-01-01

The influence of boron to nitrogen ratio, strain rate and cooling rate on hot ductility of aluminium-killed, low carbon, boron microalloyed steel was investigated. Hot tensile testing was performed on steel samples reheated in argon to 1300 deg. C, cooled at rates of 0.3, 1.2 and 3.0 deg. C s -1 to temperatures in the range 750-1050 deg. C, and then strained to failure at initial strain rates of 1 x 10 -4 or 1 x 10 -3 s -1 . It was found that the steel with a B:N ratio of 0.19 showed deep hot ductility troughs for all tested conditions; the steel with a B:N ratio of 0.47 showed a deep ductility trough for a high cooling rate of 3.0 deg. C s -1 and the steel with a near-stoichiometric B:N ratio of 0.75 showed no ductility troughs for the tested conditions. The ductility troughs extended from ∼900 deg. C (near the Ae 3 temperature) to ∼1000 or 1050 deg. C in the single-phase austenite region. The proposed mechanism of hot ductility improvement with increase in B:N ratio in these steels is that the B removes N from solution, thus reducing the strain-induced precipitation of AlN. Additionally, BN co-precipitates with sulphides, preventing precipitation of fine MnS, CuS and FeS, and forming large, complex precipitates that have no effect on hot ductility

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.

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.

Evaluation of a Ductility after High Temperature Oxidation with the Three-Point Bend Test in Zirconium Alloys

International Nuclear Information System (INIS)

Jung, Yang Il; Park, Sang Yoon; Park, Jeong Yong; Jeong, Yong Hwan

2010-01-01

In a light water reactor, the fuel cladding play an important role of preventing leakage of radioactive materials into the coolant, and thus the mechanical integrity of the cladding should be guaranteed under the conditions of normal and transient operation. In the case of a loss of coolant accident (LOCA), the cladding is subjected to a high temperature oxidation which is finally quenched because of an emergency coolant reflooding into the core. In this situation, the current LOCA criteria consist of five separate requirements: i) peak cladding temperature, ii) maximum cladding oxidation, iii) maximum hydrogen generation, iv) coolable geometry, and v) long-term cooling. The claddings lose their ductility due to the microstructural phase transformation from beta to martensite alpha-prime. and hydrogen up-take after LOCA. Since the reduction in ductility can induce embrittlement of claddings, post-quench ductility is one of the major concerns in transient operation circumstances. For the analysis, usually ring compression test are performed on ring samples cut from the tube to examine the oxidized cladding ductility. However, the test would not be applicable to the platelet samples which are general form of a specimen for developing alloys. As a high burn-up fuel cladding materials, Zircaloys are being replaced by modern zirconium alloys such as ZIRLO, and M5. Korea has also developed a new fuel cladding material HANA (high performance alloy for nuclear application) by the Korea Atomic Energy Research Institute. Because of the different composition of the newer claddings in comparison with the conventional Zircaloy-4, the high temperature oxidation behavior and the ductility after the oxidation would be different, and the properties should be evaluated how much the newer claddings were improved

Hot Ductility Behavior of a Peritectic Steel during Continuous Casting

OpenAIRE

Arıkan, Mustafa

2015-01-01

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 ...

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

Science.gov (United States)

2016-08-01

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

High Strain Rate Tensile Testing of Silver Nanowires: Rate-Dependent Brittle-to-Ductile Transition.

Science.gov (United States)

Ramachandramoorthy, Rajaprakash; Gao, Wei; Bernal, Rodrigo; Espinosa, Horacio

2016-01-13

The characterization of nanomaterials under high strain rates is critical to understand their suitability for dynamic applications such as nanoresonators and nanoswitches. It is also of great theoretical importance to explore nanomechanics with dynamic and rate effects. Here, we report in situ scanning electron microscope (SEM) tensile testing of bicrystalline silver nanowires at strain rates up to 2/s, which is 2 orders of magnitude higher than previously reported in the literature. The experiments are enabled by a microelectromechanical system (MEMS) with fast response time. It was identified that the nanowire plastic deformation has a small activation volume (ductile failure mode transition was observed at a threshold strain rate of 0.2/s. Transmission electron microscopy (TEM) revealed that along the nanowire, dislocation density and spatial distribution of plastic regions increase with increasing strain rate. Furthermore, molecular dynamic (MD) simulations show that deformation mechanisms such as grain boundary migration and dislocation interactions are responsible for such ductility. Finally, the MD and experimental results were interpreted using dislocation nucleation theory. The predicted yield stress values are in agreement with the experimental results for strain rates above 0.2/s when ductility is pronounced. At low strain rates, random imperfections on the nanowire surface trigger localized plasticity, leading to a brittle-like failure.

Ultrasonic testing of pre-turned contours for large components made of ductile iron

International Nuclear Information System (INIS)

Schmitte, Till; Chichkov, Nikolai; Nemitz, Oliver; Orth, Thomas; Hocks, Heinrich Jr.; Rusche, Sascha; Opalla, Dirk; Frank, Joerg

2015-01-01

In the ultrasonic testing of large, thick-walled components made of ductile iron partial acoustic paths of several meters are needed. Considered here are cylindrical components such as the body of CASTOR containers with diameters 2-3 m, a height of up to 6 m and a wall thickness of 500 mm. So far, an automated technique for this is not available, therefore such components are checked in a complex and lengthy process by manual ultrasonic testing. The development and design of the testing by means of simulations and the realization as a mobile testing device are topics of this paper. Measurements on a reference body with test reflectors in different depths are presented and discussed. [de

Hot Ductility Behavior of Boron Containing Microalloyed Steels with Varying Manganese Contents

Science.gov (United States)

Brune, Tobias; Senk, Dieter; Walpot, Raphael; Steenken, Bernhard

2015-02-01

The hot ductility is measured for six different steel grades with different microalloying elements and with varying manganese contents using the hot tensile test machine with melting/solidification unit at the Department of Ferrous Metallurgy RWTH Aachen University. To identify the influence of manganese on hot ductility, tests are performed with varying the manganese content from 0.7 to 18.2 wt pct, a high manganese steel. Additionally, the effect of different cooling and strain rates is analyzed by changing the particular rate for selected samples in the minima. To investigate and detect the cause of cracking during testing, the fracture surfaces in the ductility minima are considered with scanning electron microscope-energy dispersive X-ray spectroscopy. Thermodynamic modeling is conducted on basis of the commercial software ThermoCalc©. A sharp decrease of the hot ductility is recognizable at 1398 K (1125 °C), at only 0.7 wt pct manganese because of the low manganese to sulfur ratio. The grades with a Mn content up to 1.9 wt pct show a good ductility with minimal ductility loss. In comparison, the steel grade with 18.2 wt pct has a poor hot ductility. Because of the formation of complex precipitates, where several alloying elements are involved, the influence of boron on hot ductility is not fully clarified. By increasing the cooling rate, the reduction of area values are shifted to smaller values. For high test temperatures, these measured values are decreased for lower strain rates. Thereby, an early drop of the ductility is noticeable for the high temperatures around 1373 K (1100 °C).

Microstructural effects of ductile phase toughening of Nb-Nb silicide composites

International Nuclear Information System (INIS)

Lewandowski, J.J.; Dimiduk, D.; Kerr, W.; Menddiratta, M.G.

1988-01-01

In the Nb-Si system, the terminal Nb phase and Nb 5 Si 3 phase are virtually immiscible up to approximately 2033k. This system offers the potential of producing composites consisting of a ductile refractory metal phase and a strong intermetallic phase. In-situ composites containing different volume fractions of the ductile Nb phase were produced via vacuum arc-casting. Microhardness testing as well as smooth bend bar testing was conducted at temperatures ranging from 298k to 1673k in an attempt to determine microstructural effects on the yield strength and smooth bar fracture strength. Notched bend specimens were similarly tested to determine the effects of the ductile phase (i.e. Nb) on enhancing the notched bend toughness. It is shown that Nb phase often behaves in a ductile manner during testing, thereby toughening the in-situ composite. The mechanism of toughening appears to be due to crack bridging

Hot ductility of continuously cast structural steels

International Nuclear Information System (INIS)

Pytel, S.M.

1995-01-01

The objective of this investigation was to explain the hot ductility of the structural steels characterized by different amount of carbon and morphology of sulfides. Two different rolling processes were simulated under computer controlled, high temperature deformation MTS system. Results of this study show that morphology of sulfides as well as temperature and amount of deformation are responsible for level of hot ductility of the steel tested. (author)

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.

High temperature ductility of austenitic alloys exposed to thermal neutrons

International Nuclear Information System (INIS)

Watanabe, K.; Kondo, T.; Ogawa, Y.

1982-01-01

Loss of high temperature ductility due to thermal neutron irradiation was examined by slow strain rate test in vacuum up to 1000 0 C. The results on two heats of Hastelloy alloy X with different boron contents were analyzed with respect to the influence of the temperatures of irradiation and tensile tests, neutron fluence and the associated helium production due to nuclear transmutation reaction. The loss of ductility was enhanced by increasing either temperature or neutron fluence. Simple extrapolations yielded the estimated threshold fluence and the end-of-life ductility values at 900 and 1000 0 C in case where the materials were used in near-core regions of VHTR. The observed relationship between Ni content and the ductility loss has suggested a potential utilization of Fe-based alloys for seathing of the neutron absorber materials

Unstable ductile fracture conditions in upper shelf region

International Nuclear Information System (INIS)

Nakano, Yoshifumi; Kubo, Takahiro

1985-01-01

The phenomenon of unstability of ductile fracture in the upper shelf region of a forged steel for nuclear reactor pressure vessels A508 Cl. 3 was studied with a large compliance apparatus, whose spring constants were 100, 170 and 230 kgf/mm, at the test temperatures of 100, 200 and 300 0 C and at the loading rates of 2, 20 and 200 mm/min in the crosshead speed. The main results obtained are as follows: (1) The fracture modes of the specimens consisted of (a) stable fracture, (b) unstable fracture which leads to a complete fracture rapidly and (c) quasiunstable fracture which does not lead to a complete fracture though a rapid extension of ductile crack takes place. (2) Side groove, high temperature or small spring constant made a ductile crack more unstable. (3) High temperature or large spring constant made the occurrence of quasiunstable fracture easier. (4) Quasiunstable ductile fracture took place before the maximum load, that is, at the J integral value of about 10 kgf/mm. The initiation of a microscopic ductile crack, therefore, seems to lead to quasiunstable fracture. (5) The concept that unstable ductile fracture takes place when Tsub(app) exceeds Tsub(mat) seems applicable only to the case in which unstable ductile fracture takes place after the maximum load has been exceeded. (author)

Analyses of cavitation instabilities in ductile metals

DEFF Research Database (Denmark)

Tvergaard, Viggo

2007-01-01

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......, 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......, while the surrounding voids are represented by a porous ductile material model in terms of a field quantity that specifies the variation of the void volume fraction in the surrounding metal....

Ductility and fracture of single crystaliine Ni3Al with boron additions

International Nuclear Information System (INIS)

Heredia, F.E.; Pope, D.P.

1989-01-01

Low and high temperature tensile tests were performed on single crystals of pure Ni 3 Al and Ni 3 Al+B in order to determine the effect of B additions on the ductility and fracture behavior. Tests were carried out in air at a constant strain rate of 1/3 x 10 -3 s -1 . The orientation tested were [001] for whic the yield stress in tension is always greater than in compression, and those for wich the tension/compression asymmetry is zero ([T=C]) for each particular composition. At room temperature, the results show a positive effect of B additions on both the fracture stress and on the ductility. The ductility at 800K appears to decrease monotonically with B additions. The largest ductilities are found for [T=C] at room temperature where an improvement of about 26% (resolved strain) for an addition of 0.2 at % B was obtained. However, the most dramatic increase in ductility occurs for the [001] oriented samples at room temperature where a 55% improvement was measured over that of pure Ni 3 Al. Fracture surfaces show a combinaton of massive slip, some clevage, and heavily dimpled areas. These observations show that B additions not only increase the ductility of polycrystalline Ni 3 Al, as has been previously observed by many investigators, but also that the already-ductile single crystalline material, indicating that a bulk effect should be added to the grain boundary strengthening effect of B when explaining the improvement in ductility of polycrystalline Ni 3 Al due to B additions

Ductility and fracture behavior of polycrystalline Ni/sub 3/Al alloys

International Nuclear Information System (INIS)

Liu, C.T.

1987-01-01

This paper provides a comprehensive review of the recent work on tensile ductility and fracture behavior of Ni/sub 3/Al alloys tested at ambient and elevated temperatures. Polycrystalline Ni/sub 3/Al is intrinsically brittle along grain boundaries, and the brittleness has been attributed to the large difference in valency, electronegativity, and atom size between nickel and aluminum atoms. Alloying with B, Mn, Fe, and Be significantly increases the ductility and reduces the propensity for intergranular fracture in Ni/sub 3/Al alloys. Boron is found to be most effective in improving room-temperature ductility of Ni/sub 3/Al with <24.5 at.% Al. The tensile ductility of Ni/sub 3/Al alloys depends strongly on test environments at elevated temperatures, with much lower ductilities observed in air than in vacuum. The loss in ductility is accompanied by a change in fracture mode from transgranular to intergranular. This embrittlement is due to a dynamic effect involving simultaneously high localized stress, elevated temperature, and gaseous oxygen. The embrittlement can be alleviated by control of grain shape or alloying with chromium additions. All the results are discussed in terms of localized stress concentration and grain-boundary cohesive strength

Investigation of the hot ductility of a high-strength boron steel

International Nuclear Information System (INIS)

Güler, Hande; Ertan, Rukiye; Özcan, Reşat

2014-01-01

In this study, the high-temperature ductility behaviour of an Al–Si-coated 22MnB5 sheet was investigated. The mechanical properties of Al–Si-coated 22MnB5 boron steel were examined via hot tensile tests performed at temperatures ranging from 400 to 900 °C at a strain rate of 0.083 s −1 . The deformation and fracture mechanisms under hot tensile testing were considered in relation to the testing data and to the fracture-surface observations performed via SEM. The hot ductility of the tested boron steel was observed as a function of increasing temperature and the Al–Si-coated 22MnB5 boron steel exhibited a ductility loss at 700 °C

Value/impact of design criteria for cast ductile iron shipping casks

International Nuclear Information System (INIS)

1983-01-01

The ductile failure criteria proposed in the Base report appear appropriate except that stress intensity values, S/sub m/ should be based on lower safety factors and ductility should be added as a criterion. A safety factor for stress intensity, s/sub m/ of 4 is recommended rather than 3 on minimum ultimate tensile strength, S/sub u/ in accordance with ASME code philosophy of assigning higher safety factors to cast ductile iron than to steel. This more conservative approach has no impact on costs since the selection of wall thickness is controlled by shielding rather than by stress considerations. The addition of a ductility criterion is recommended because of the problems associated with the selection of appropriate brittle failure criteria and the potential for cast ductile iron to have extremely low elongation at failure. Neither a materials nor a linear elastic fracture mechanics (LEFM) approach appear to be viable for demonstrating the prevention of brittle failure in cast ductile iron shipping casks. It is possible that the analytic methods predict brittle failure because of extremely conservative assumptions whereas real casks may not fail. Model drop tests could be used to demonstrate containment integrity. It is estimated that a risk committment of at least $1,000,000 would be required for engineering, design, model fabrication and testing. Before taking such risks, a mechanism should be found to obtain concurrence from NRC that the results of the test would be acceptable. Probabilistic approaches or model testing could be used to demonstrate the acceptability of cast ductile iron casks from a brittle failure point of view. Before probabilistic methods can be used, the NRC would have to be persuaded to accept the approach of the Competent Authority in West Germany or more formalized methods for probabilistic risk assessments

Ductile-brittle transition of thoriated chromium.

Science.gov (United States)

Wilcox, B. A.; Veigel, N. D.; Clauer, A. H.

1972-01-01

Unalloyed chromium and chromium containing approximately 3 wt % ThO2 were prepared from powder produced by a chemical vapor deposition process. When rolled to sheet and tested in tension, it was found that the thoriated material had a lower ductile-to-brittle transition temperature (DBTT) than unalloyed chromium. This ductilizing was evident both in the as-rolled condition and after the materials had been annealed for 1 hour at 1200 C. The improved ductility in thoriated chromium may be associated with several possible mechanisms: (1) particles may disperse slip, such that critical stress or strain concentrations for crack nucleation are more difficult to achieve; (2) particles may act as dislocation sources, thus providing mobile dislocations in this normally source-poor material, in a manner similar to prestraining; and (3) particles in grain boundaries may help to transmit slip across the boundaries, thus relieving stress concentrations and inhibiting crack nucleation.

Effect of low fatigue on the ductile-brittle transition of molybdenum

International Nuclear Information System (INIS)

Furuya, K.; Nagata, N.; Watanabe, R.; Yoshida, H.

1982-01-01

An explicit ductile-brittle transition of molybdenum occurring in both tensile and low cycle fatigue tests was investigated. Tests were performed on several sorts of molybdenum and its alloy TZM, and effects of heat treatment, fabrication method and alloying on the transition behavior and fracture mode are described in detail. All the materials exhibited a brittle failure with degraded fatigue behavior at room temperature, while they became ductile as temperature increased up to 573 K. The tendency of fatigue results was qualitatively in accordance with that of reduction of area in tensile tests. Differences among the materials were minor on the ductile-brittle transition temperature (DBTT), but major on the fatigue life for the embrittled materials. (orig.)

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.

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

Hot ductility behavior of a low carbon advanced high strength steel (AHSS) microalloyed with boron

International Nuclear Information System (INIS)

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

2011-01-01

Research highlights: → Effect of boron on the hot ductility behavior of a low carbon NiCrVCu AHSS. → Boron addition of 117 ppm improves hot ductility over 100% in terms of RA. → Hot ductility improvement is associated with segregation/precipitation of boron. → Typical hot ductility recovery at lower temperatures does not appear in this steel. → Hot ductility loss is associated with precipitates/inclusions coupled with voids. - Abstract: The current study analyses the influence of boron addition on the hot ductility of a low carbon advanced high strength NiCrVCu steel. For this purpose hot tensile tests were carried out at different temperatures (650, 750, 800, 900 and 1000 deg. C) at a constant true strain rate of 0.001 s -1 . Experimental results showed a substantial improvement in hot ductility for the low carbon advanced high strength steel when microalloyed with boron compared with that without boron addition. Nevertheless, both steels showed poor ductility when tested at the lowest temperatures (650, 750 and 800 deg. C), and such behavior is associated to the precipitation of vanadium carbides/nitrides and inclusions, particularly MnS and CuS particles. The fracture mode of the low carbon advanced high strength steel microalloyed with boron seems to be more ductile than the steel without boron addition. Furthermore, the fracture surfaces of specimens tested at temperatures showing the highest ductility (900 and 1000 deg. C) indicate that the fracture mode is a result of ductile failure, while in the region of poor ductility the fracture mode is of the ductile-brittle type failure. It was shown that precipitates and/or inclusions coupled with voids play a meaningful role on the crack nucleation mechanism which in turn causes a hot ductility loss. Likewise, dynamic recrystallization (DRX) which always results in restoration of ductility only occurs in the range from 900 to 1000 deg. C. Results are discussed in terms of boron segregation towards

Hot ductility behavior of a low carbon advanced high strength steel (AHSS) microalloyed with boron

Energy Technology Data Exchange (ETDEWEB)

Mejia, I., E-mail: imejia@umich.mx [Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio ' U' , Ciudad Universitaria, 58066 Morelia, Michoacan (Mexico); Bedolla-Jacuinde, A.; Maldonado, C. [Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio ' U' , Ciudad Universitaria, 58066 Morelia, Michoacan (Mexico); Cabrera, J.M. [Departament de Ciencia dels Materials i Enginyeria Metal.lurgica, ETSEIB - Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundacio CTM Centre Tecnologic, Av. de las Bases de Manresa 1, 08240 Manresa (Spain)

2011-05-25

Research highlights: {yields} Effect of boron on the hot ductility behavior of a low carbon NiCrVCu AHSS. {yields} Boron addition of 117 ppm improves hot ductility over 100% in terms of RA. {yields} Hot ductility improvement is associated with segregation/precipitation of boron. {yields} Typical hot ductility recovery at lower temperatures does not appear in this steel. {yields} Hot ductility loss is associated with precipitates/inclusions coupled with voids. - Abstract: The current study analyses the influence of boron addition on the hot ductility of a low carbon advanced high strength NiCrVCu steel. For this purpose hot tensile tests were carried out at different temperatures (650, 750, 800, 900 and 1000 deg. C) at a constant true strain rate of 0.001 s{sup -1}. Experimental results showed a substantial improvement in hot ductility for the low carbon advanced high strength steel when microalloyed with boron compared with that without boron addition. Nevertheless, both steels showed poor ductility when tested at the lowest temperatures (650, 750 and 800 deg. C), and such behavior is associated to the precipitation of vanadium carbides/nitrides and inclusions, particularly MnS and CuS particles. The fracture mode of the low carbon advanced high strength steel microalloyed with boron seems to be more ductile than the steel without boron addition. Furthermore, the fracture surfaces of specimens tested at temperatures showing the highest ductility (900 and 1000 deg. C) indicate that the fracture mode is a result of ductile failure, while in the region of poor ductility the fracture mode is of the ductile-brittle type failure. It was shown that precipitates and/or inclusions coupled with voids play a meaningful role on the crack nucleation mechanism which in turn causes a hot ductility loss. Likewise, dynamic recrystallization (DRX) which always results in restoration of ductility only occurs in the range from 900 to 1000 deg. C. Results are discussed in terms of

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)

Combined effects of radiation damage and hydrides on the ductility of Zircaloy-2

International Nuclear Information System (INIS)

Wisner, S.B.; Adamson, R.B.

1998-01-01

Interest remains high regarding the effects of zirconium hydride precipitates on the ductility of reactor Zircaloy components, particularly in irradiated material. Previous studies have reported that ductility reductions are much greater at room temperature compared to reactor component temperatures. It is often concluded that the effects of irradiation dominate the ductility reduction observed in test specimens, although there is no consensus as to whether hydriding effects are additive. Many of the tests reported in the literature are difficult to interpret due to variations in test specimen geometry and material history. In this paper, we present the results of an experimental program aimed at clearly describing the combined effects of irradiation and hydriding on ductility parameters under conditions of a realistic test specimen design and well characterized hydride content, distribution and orientation. Experiments were conducted at 295 and 605 K, respectively on Zircaloy-2 tubing segments containing 10-800 ppm hydrogen and neutron fluences between 0.9 x 10 25 nm -2 (E>1 MeV). Tests utilized the well proven localized ductility specimen which applies plane strain tension in the hoop direction of the tubing segment. In all cases, hydrides were also oriented in the hoop or circumferential direction and were uniformly distributed across the tubing wall. Results indicate that at 605 K, the ductility of irradiated material was almost independent of hydride content, retaining above 4% uniform elongation and 25% reduction in an area for the highest fluences and hydrogen contents. Even at 295 K, measurable ductility was retained for irradiated material with up to 600 ppm hydrogen. In the paper, results of fractographic analyses and strain rate are also discussed

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.

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.

Hot ductility behavior of near-alpha titanium alloy IMI834

International Nuclear Information System (INIS)

Ghavam, Mohammad Hadi; Morakabati, Maryam; Abbasi, Seyed Mahdi; Badri, Hassan

2014-01-01

The hot ductility of rolled IMI834 titanium alloy (Ti-5.3Al-2.9Sn-3.0Zr-0.65Nb-0.5Mo-0.2Si in wt%) has been studied by conducting tensile tests with a strain rate of 0.1 s -1 and temperature range of 750-1100 C to obtain the optimum hot working conditions. The alloy showed minimum hot ductility in the lower alpha-beta region in the temperature range 750-950 C. Further microstructural characterizations showed improvement in hot ductility by increasing temperature, which was attributed to reduction of volume fraction of high strength alpha phase. The best hot ductility was observed at 1000 C, i.e. in the upper alpha-beta region. The better hot ductility at higher temperature could be related to the increase in the volume fraction of beta phase and the occurrence of dynamic restoration phenomena. The second decline in hot ductility appeared at higher temperatures in the beta region and was attributed to the high stacking fault energy and self-diffusion of beta phase leading to limitation of dynamic recrystallization.

Hot Ductility of the 17-4 PH Stainless Steels

Science.gov (United States)

Herrera Lara, V.; Guerra Fuentes, L.; Covarrubias Alvarado, O.; Salinas Rodriguez, A.; Garcia Sanchez, E.

2016-03-01

The mechanisms of loss of hot ductility and the mechanical behavior of 17-4 PH alloys were investigated using hot tensile testing at temperatures between 700 and 1100 °C and strain rates of 10-4, 10-2, and 10-1 s-1. Scanning electron microscopy was used in conjunction with the results of the tensile tests to find the temperature region of loss of ductility and correlate it with cracking observed during processing by hot upsetting prior to ring rolling. It is reported that 17-4 PH alloys lose ductility in a temperature range around 900 °C near to the duplex austenite + ferrite phase field. Furthermore, it is found that niobium carbides precipitated at austenite/ferrite interfaces and grain boundaries have a pronounced effect on the mechanical behavior of the alloy during high-temperature deformation.

Hot ductility of a microalloyed steel in the intermediate temperature range

International Nuclear Information System (INIS)

Darsouni, A.; Bouzabata, B.; Montheillet, F.

1995-01-01

In this study hot ductility has been determined from tensile tests for two states of a microalloyed steel: after casting and after rolling processes. Hot deformations were carried out at speeds varying from 10 -4 s -1 to 10 -2 s -1 and temperatures from 750 C to 1100 C. Two heat treatments were chosen before hot deformation. A ferrite precipitation is observed at austenitic grain boundaries in the intercritical temperature range, causing intergranular embrittlement. Ductility trough is deeper in the as-cast samples due to the growth of large grain size. Also, precipitation makes the hot ductility curve wider and deeper around 900 C. The results show a decrease in hot ductility. Minimum values of hot ductility are determined for (ITC) treatment at 900 C and for (DTC) treatment at 800 C. For this second treatment another decrease in hot ductility was observed at 900 C. We can explain hot ductility losses by the presence of precipitates in the austenitic region and the presence of the two-phase structure in the intercritical region. (orig.)

Alloy-dependent deformation behavior of highly ductile nanocrystalline AuCu thin films

International Nuclear Information System (INIS)

Lohmiller, Jochen; Spolenak, Ralph; Gruber, Patric A.

2014-01-01

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

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.

Room-temperature ductile inorganic semiconductor

Science.gov (United States)

Shi, Xun; Chen, Hongyi; Hao, Feng; Liu, Ruiheng; Wang, Tuo; Qiu, Pengfei; Burkhardt, Ulrich; Grin, Yuri; Chen, Lidong

2018-05-01

Ductility is common in metals and metal-based alloys, but is rarely observed in inorganic semiconductors and ceramic insulators. In particular, room-temperature ductile inorganic semiconductors were not known until now. Here, we report an inorganic α-Ag2S semiconductor that exhibits extraordinary metal-like ductility with high plastic deformation strains at room temperature. Analysis of the chemical bonding reveals systems of planes with relatively weak atomic interactions in the crystal structure. In combination with irregularly distributed silver-silver and sulfur-silver bonds due to the silver diffusion, they suppress the cleavage of the material, and thus result in unprecedented ductility. This work opens up the possibility of searching for ductile inorganic semiconductors/ceramics for flexible electronic devices.

Simulation of the ductile damage under the metal forming

International Nuclear Information System (INIS)

Bogatov, A. A.

2003-01-01

Potentiality of metal forming is limited by ductile damage. The damage degree is estimated by the scalar value ω, that is equal to 0(ω=0) before plastic strain and is equal to 1(ω=1) at the macro cracks moment. There are two criteria that describe micro damage. The value ω=ω * corresponds to the generation of micro voids that couldn't be recovered by recrystallization but do not reduce the metal strength. The value ω=ω ** corresponds to the generation of micro voids that reduce the metal strength and material long life. The models of metal damage accumulation under pure and alternate strain also the model of metal damage recovery under the recrystallization are developed. The specimen testing at high loading parameters gives the basic equations of the ductile damage mechanics. All of that gives the method to study ductile damage under the metal forming. The methodology damage nucleation and growing is shown on various examples: the void and crack development in the areas ductile damage and unlimited ductility; mathematical simulation of the metal damage under the sheet and wire drawing and others. The problems of physical simulating at the ductile damage under metal forming are shown too in this paper. The method and equipment of metal damage physical simulation are proposed. (Original)

Ductile-to-brittle transition behavior of tungsten-copper composites

International Nuclear Information System (INIS)

Hiraoka, Y.; Inoue, T.; Akiyoshi, N.; Yoo, M.K.

2001-01-01

A series of W-Cu composites were fabricated alternatively by infiltration method (19-48 vol% Cu) or by pressing and sintering method (20-80 vol% Cu), and three-point bend tests were carried out at temperatures between 77 and 363 K. Ductile-to-brittle transition behavior of the composite was investigated and also effects of Cu content as well as fabrication method on the strength and ductility of the composite were discussed. Results were summarized as follows. (1) Composite containing 19-40 vol% of copper demonstrated ductile-to-brittle transition behavior. Transition temperature tended to decrease substantially with increasing Cu content, though ductility of the composite by infiltration method was much better than that by pressing and sintering method. (2) Composite containing 48-80 vol% of copper did not demonstrate transition behavior regardless of fabrication method. (3) These results were well interpreted in terms of microstructure and fractography. (author)

Hot Ductility Characterization of Sanicro-28 Super-Austenitic Stainless Steel

Science.gov (United States)

Mirzaei, A.; Zarei-Hanzaki, A.; Abedi, H. R.

2016-05-01

The hot ductility behavior of a super-austenitic stainless steel has been studied using tensile testing method in the temperature range from 1073 K to 1373 K (800 °C to 1100 °C) under the strain rates of 0.1, 0.01, and 0.001 s-1. The hot compression tests were also performed at the same deformation condition to identify the activated restoration mechanisms. At lower temperatures [ i.e., 1073 K and 1173 K (800 °C and 900 °C)], the serration of initial grain boundaries confirms the occurrence of dynamic recovery as the predominant restoration process. However, in the course of applied deformation, the initial microstructure is recrystallized at higher temperatures [ i.e., 1273 K and 1373 K (1000 °C and 1100 °C)]. In this respect, annealing the twin boundaries could well stimulate the recrystallization kinetic through initiation new annealing twins on prior annealing twin boundaries. The hot tensile results show that there is a general trend of increasing ductility by temperature. However, two regions of ductility drop are recognized at 1273 K and 1373 K (1000°C)/0.1s-1 and (1100°C)/0.01s-1. The ductility variations at different conditions of temperature and strain rate are discussed in terms of simultaneous activation of grain boundary sliding and restoration processes. The observed ductility troughs are attributed to the occurrence of grain boundary sliding and the resulting R-type and W-type cracks. The occurrence of dynamic recrystallization is also considered as the main factor increasing the ductility at higher temperatures. The enhanced ductility is primarily originated from the post-uniform elongation behavior, which is directly associated with the strain rate sensitivity of the experimental material.

Alloying effect of 3D transition elements on the ductility of chromium

International Nuclear Information System (INIS)

Matsumoto, Y.; Fukumori, J.; Morinaga, M.; Furui, M.; Nambu, T.; Sakaki, T.

1996-01-01

Chromium and its alloys have good corrosion resistance in corrosive environments and good oxidation resistance at high temperatures. In addition, they exhibit an excellent combination of low density and high creep strength. However, there is still a large barrier to the practical use because of their poor ductility at room temperature. According to recent investigations, an environmental effect was found on the ductility of high purity polycrystalline chromium. In this study, in order to find a way to improve the ductility of chromium at room temperature, the alloying effect on the ductility of chromium was investigated experimentally in several test environments

Ductile growth of crack like flawing during hydrotest; Propagacao dutil de defeitos planares durante teste hidrostatico

Energy Technology Data Exchange (ETDEWEB)

Teixeira, Jose C; Donato, Guilherme V [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES); Silva, Marcinei S. da; Bastian, Fernando L [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE); Lima, Romulo S. de [PETROBRAS/AB-RE, Rio de Janeiro, RJ (Brazil)

2003-07-01

In this paper effects of hydrostatic testing on ductile propagation of crack like flaw defects were evaluated in API X-60 steel. The model used was based on the J-tearing theory, supported by elastic - plastic fracture mechanics. The J-initiation resistance values (JIc) were determined by fracture mechanic tests using potential drop technique and compact test specimen. The JIc values were also determined from flow stress and Charpy V-notch at plateau, which are both usually available in mill-test data. Despite of being based on small database it seems it could be extended and it will be useful for future analysis. (author)

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.

Ductile Crack Initiation Criterion with Mismatched Weld Joints Under Dynamic Loading Conditions.

Science.gov (United States)

An, Gyubaek; Jeong, Se-Min; Park, Jeongung

2018-03-01

Brittle failure of high toughness steel structures tends to occur after ductile crack initiation/propagation. Damages to steel structures were reported in the Hanshin Great Earthquake. Several brittle failures were observed in beam-to-column connection zones with geometrical discontinuity. It is widely known that triaxial stresses accelerate the ductile fracture of steels. The study examined the effects of geometrical heterogeneity and strength mismatches (both of which elevate plastic constraints due to heterogeneous plastic straining) and loading rate on critical conditions initiating ductile fracture. This involved applying the two-parameter criterion (involving equivalent plastic strain and stress triaxiality) to estimate ductile cracking for strength mismatched specimens under static and dynamic tensile loading conditions. Ductile crack initiation testing was conducted under static and dynamic loading conditions using circumferentially notched specimens (Charpy type) with/without strength mismatches. The results indicated that the condition for ductile crack initiation using the two parameter criterion was a transferable criterion to evaluate ductile crack initiation independent of the existence of strength mismatches and loading rates.

49 CFR 192.277 - Ductile iron pipe.

Science.gov (United States)

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Ductile iron pipe. 192.277 Section 192.277 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Ductile iron pipe. (a) Ductile iron pipe may not be joined by threaded joints. (b) Ductile iron pipe may...

Hot Ductility Behavior of an 8 Pct Cr Roller Steel

Science.gov (United States)

Wang, Zhenhua; Sun, Shuhua; Shi, Zhongping; Wang, Bo; Fu, Wantang

2015-04-01

The hot ductility of an 8 pct Cr roller steel was determined between 1173 K and 1473 K (900 °C and 1200 °C) at strain rates of 0.01 to 10 s-1 through tensile testing. The fracture morphology was observed using scanning electron microscopy, and the microstructure was examined through optical microscopy and transmission electron microscopy. The dependence of the hot ductility behavior on the deformation conditions, grain size, and precipitation was analyzed. The relationship between the reduction in area and the natural logarithm of the Zener-Hollomon parameter (ln Z) was found to be a second-order polynomial. When ln Z was greater than 40 s-1, the hot ductility was poor and fracture was mainly caused by incompatible deformation between the grains. When ln Z was between 32 and 40 s-1, the hot ductility was excellent and the main fracture mechanism was void linking. When ln Z was below 32 s-1, the hot ductility was poor and fracture was mainly caused by grain boundary sliding. A fine grain structure is beneficial for homogenous deformation and dynamic recrystallization, which induces better hot ductility. The effect of M7C3 carbide particles dispersed in the matrix on the hot ductility was small. The grain growth kinetics in the 8 pct Cr steel were obtained between 1373 K and 1473 K (1100 °C and 1200 °C). Finally, optimized preheating and forging procedures for 8 pct Cr steel rollers are provided.

Micromechanics based simulation of ductile fracture in structural steels

Science.gov (United States)

Yellavajjala, Ravi Kiran

The broader aim of this research is to develop fundamental understanding of ductile fracture process in structural steels, propose robust computational models to quantify the associated damage, and provide numerical tools to simplify the implementation of these computational models into general finite element framework. Mechanical testing on different geometries of test specimens made of ASTM A992 steels is conducted to experimentally characterize the ductile fracture at different stress states under monotonic and ultra-low cycle fatigue (ULCF) loading. Scanning electron microscopy studies of the fractured surfaces is conducted to decipher the underlying microscopic damage mechanisms that cause fracture in ASTM A992 steels. Detailed micromechanical analyses for monotonic and cyclic loading are conducted to understand the influence of stress triaxiality and Lode parameter on the void growth phase of ductile fracture. Based on monotonic analyses, an uncoupled micromechanical void growth model is proposed to predict ductile fracture. This model is then incorporated in to finite element program as a weakly coupled model to simulate the loss of load carrying capacity in the post microvoid coalescence regime for high triaxialities. Based on the cyclic analyses, an uncoupled micromechanics based cyclic void growth model is developed to predict the ULCF life of ASTM A992 steels subjected to high stress triaxialities. Furthermore, a computational fracture locus for ASTM A992 steels is developed and incorporated in to finite element program as an uncoupled ductile fracture model. This model can be used to predict the ductile fracture initiation under monotonic loading in a wide range of triaxiality and Lode parameters. Finally, a coupled microvoid elongation and dilation based continuum damage model is proposed, implemented, calibrated and validated. This model is capable of simulating the local softening caused by the various phases of ductile fracture process under

Effect of transient liquid phase (TLP) bonding on the ductility of a Ni-base single crystal superalloy in a stress rupture test

International Nuclear Information System (INIS)

Liu, J.D.; Jin, T.; Zhao, N.R.; Wang, Z.H.; Sun, X.F.; Guan, H.R.; Hu, Z.Q.

2008-01-01

A Ni-base single crystal superalloy was transient liquid phase (TLP) bonded using a Ni-Cr-B amorphous foil at 1230 deg. C for 8 h. Stress rupture tests of the TLP joint and a matrix sample were carried out at 982 deg. C/248 MPa and 1010 deg. C/248 MPa. The microstructures and fracture surfaces were studied using scanning electron microscopy (SEM). Transmission electron microscopy (TEM) investigations were performed after creep rupture testing to examine the deformation substructures. The results show that the stress rupture ductility of TLP joints is significantly decreased compared to the matrix sample. This reduction of the ductility of TLP joints can be attributed to solid solution strengthening by boron atoms, subgrain boundaries formed in the bonding zone and the concentration of creep cavities formed during the last stage of the stress rupture test

New measurement technique of ductility curve for ductility-dip cracking susceptibility in Alloy 690 welds

Energy Technology Data Exchange (ETDEWEB)

Kadoi, Kota, E-mail: kadoi@hiroshima-u.ac.jp [Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527 (Japan); Uegaki, Takanori; Shinozaki, Kenji; Yamamoto, Motomichi [Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527 (Japan)

2016-08-30

The coupling of a hot tensile test with a novel in situ observation technique using a high-speed camera was investigated as a high-accuracy quantitative evaluation method for ductility-dip cracking (DDC) susceptibility. Several types of Alloy 690 filler wire were tested in this study owing to its susceptibility to DDC. The developed test method was used to directly measure the critical strain for DDC and high temperature ductility curves with a gauge length of 0.5 mm. Minimum critical strains of 1.3%, 4.0%, and 3.9% were obtained for ERNiCrFe-7, ERNiCrFe-13, and ERNiCrFe-15, respectively. The DDC susceptibilities of ERNiCrFe-13 and ERNiCrFe-15 were nearly the same and quite low compared with that of ERNiCrFe-7. This was likely caused by the tortuosity of the grain boundaries arising from the niobium content of around 2.5% in the former samples. Besides, ERNiCrFe-13 and ERNiCrFe-15 indicated higher minimum critical strains even though these specimens include higher content of sulfur and phosphorus than ERNiCrFe-7. Thus, containing niobium must be more effective to improve the susceptibility compared to sulfur and phosphorous in the alloy system.

New measurement technique of ductility curve for ductility-dip cracking susceptibility in Alloy 690 welds

International Nuclear Information System (INIS)

Kadoi, Kota; Uegaki, Takanori; Shinozaki, Kenji; Yamamoto, Motomichi

2016-01-01

The coupling of a hot tensile test with a novel in situ observation technique using a high-speed camera was investigated as a high-accuracy quantitative evaluation method for ductility-dip cracking (DDC) susceptibility. Several types of Alloy 690 filler wire were tested in this study owing to its susceptibility to DDC. The developed test method was used to directly measure the critical strain for DDC and high temperature ductility curves with a gauge length of 0.5 mm. Minimum critical strains of 1.3%, 4.0%, and 3.9% were obtained for ERNiCrFe-7, ERNiCrFe-13, and ERNiCrFe-15, respectively. The DDC susceptibilities of ERNiCrFe-13 and ERNiCrFe-15 were nearly the same and quite low compared with that of ERNiCrFe-7. This was likely caused by the tortuosity of the grain boundaries arising from the niobium content of around 2.5% in the former samples. Besides, ERNiCrFe-13 and ERNiCrFe-15 indicated higher minimum critical strains even though these specimens include higher content of sulfur and phosphorus than ERNiCrFe-7. Thus, containing niobium must be more effective to improve the susceptibility compared to sulfur and phosphorous in the alloy system.

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...

TEM investigation of ductile iron alloyed with vanadium.

Science.gov (United States)

Dymek, S; Blicharski, M; Morgiel, J; Fraś, E

2010-03-01

This article presents results of the processing and microstructure evolution of ductile cast iron, modified by an addition of vanadium. The ductile iron was austenitized closed to the solidus (1095 degrees C) for 100 h, cooled down to 640 degrees C and held on at this temperature for 16 h. The heat treatment led to the dissolution of primary vanadium-rich carbides and their subsequent re-precipitation in a more dispersed form. The result of mechanical tests indicated that addition of vanadium and an appropriate heat treatment makes age hardening of ductile iron feasible. The precipitation processes as well as the effect of Si content on the alloy microstructure were examined by scanning and transmission electron microscopy. It was shown that adjacent to uniformly spread out vanadium-rich carbides with an average size of 50 nm, a dispersoid composed of extremely small approximately 1 nm precipitates was also revealed.

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.

Heat treatment effect on ductility of nickel-base alloys

International Nuclear Information System (INIS)

Burnakov, K.K.; Khasin, G.A.; Danilov, V.F.; Oshchepkov, B.V.; Listkova, A.I.

1979-01-01

Causes of low ductility of the KhN75MBTYu and KhN78T alloys were studied along with the heat treatment effects. Samples were tested at 20, 900, 1100, 1200 deg C. Large amount of inclusions was found in intercrystalline fractures of the above low-ductile alloys. The inclusions of two types took place: (α-Al 2 O 3 , FeO(Cr 2 O 3 xAl 2 O 3 )) dendrite-like ones and large-size laminated SiO 2 , FeO,(CrFe) 2 O 3 inclusions situated as separate colonies. Heat treatment of the alloys does not increase high-temperature impact strength and steel ductility. The heating above 1000 deg C leads to a partial dissolution and coagulation of film inclusions which results in an impact strength increase at room temperature

Effects of dead load on ductility of a floor system

International Nuclear Information System (INIS)

Fujisaki, E.; Sarkar, B.E.; Ho, H.; Reed, J.W.

1993-01-01

In seismic margin or seismic fragility calculations, the ductility scale factor F μ is often used to quantify the effect of inelastic energy absorption on structural capacity. In concept, the ductility scale factor can be thought of as a response spectrum reduction factor. For a given ductile structural element and input response spectrum, the product of F μ and the factor of safety against yield (F s ) provides a measure of the total factor of safety against failure (F). Testing and analytical studies by others have shown that structures such as shear walls and building frames (mounted vertically) subjected to horizontal input motions are capable of absorbing earthquake energy through inelastic behavior. Kennedy, 1984, Riddell, 1979, and Reed, 1991 studied the ductility scale factor and developed simplified procedures through the use of nonlinear analyses. For floor systems (mounted horizontally), we are mainly interested in the response to vertical input motions. Because of the constant downward pull of gravity, the nonlinear displacement of a floor structure is biased downward. This ratcheting phenomenon reduces the ductility scale factor for a horizontal element compared to the case where the same element is mounted vertically and is subjected to horizontal input motion. Through the use of nonlinear time history analyses, we investigated the effects of dead loads on the ductility scale factor of floor systems. We also developed a simple modification to the Riddell-Newmark procedure (Riddell, 1979), which is used to calculate the ductility scale factor for vertically mounted elements, to determine F μ for horizontally mounted elements

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

Why ductile fracture mechanics

International Nuclear Information System (INIS)

Ritchie, R.O.

1983-01-01

Until recently, the engineering application of fracture mechanics has been specific to a description of macroscopic fracture behavior in components and structural parts which remain nominally elastic under loading. While this approach, termed linear elastic fracture mechanics, has been found to be invaluable for the continuum analysis of crack growth in brittle and high strength materials, it is clearly inappropriate for characterizing failure in lower strength ductile alloys where extensive inelastic deformation precedes and accompanies crack initiation and subsequent propagation. Accordingly, much effort has been devoted in recent years toward the development of nonlinear or ductile fracture mechanics methodology to characterize fracture behavior under elastic/plastic conditions; an effort which has been principally motivated by problems in nuclear industry. In this paper, the concepts of ductile (elastic/plastic) fracture mechanics are introduced and applied to the problem of both stationary and nonstationary cracks. Specifically, the limitations inherent in this approach are defined, together with a description of the microstructural considerations and applications relevant to the failure of ductile materials by fracture, fatigue, and creep

Room temperature ductility of NiAl-strengthened ferritic steels: Effects of precipitate microstructure

International Nuclear Information System (INIS)

Teng, Z.K.; Liu, C.T.; Miller, M.K.; Ghosh, G.; Kenik, E.A.; Huang, S.; Liaw, P.K.

2012-01-01

Highlights: ► Effects of precipitate microstructure on the ductility were investigated. ► The NiAl precipitates can be systematically characterized by TEM, APT, and USAXS. ► Ductility is a function of the precipitate volume fraction. ► Ductility is closely related to the Al and Ni solubilities in the Fe matrix. ► Ductility is independent of precipitate size and inter-particle spacing. - Abstract: The effects of precipitate microstructure on the room temperature ductility of a series of carefully designed Fe–Al–Ni–Cr–Mo steels were investigated. Transmission electron microscopy (TEM), ultra small angle X-ray scattering (USAXS), and atom probe tomography (APT) were conducted to quantify the nano-scaled precipitates. The accuracy of the characterization results was verified by a numerical analysis. Three point bending tests results demonstrated that ductility was a function of the precipitate volume fraction and the Al and Ni concentrations in the Fe matrix, these relationships were discussed in terms of possible mechanisms. The ductility was also found to be independent of the precipitate size and inter-particle spacing in the studied range, which was validated by a theoretical model.

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%.

Characterizing Ductile Damage and Failure: Application of the Direct Current Potential Drop Method to Uncracked Tensile Specimens

OpenAIRE

Brinnel, V.; Döbereiner, B.; Münstermann, Sebastian

2014-01-01

Modern high-strength steels exhibit excellent ductility properties but their application is hindered by traditional design rules. A characterization of necessary safety margins for the ductile failure of these steels is therefore required. Direct observation of ductile damage within tests is currently not possible, only limited measurements can be made with synchrotron or X-ray radiation facilities. The direct current potential drop (DCPD) method can determine ductile crack propagation with l...

Grain-boundary contamination and ductility loss in boron-doped Ni3Al

International Nuclear Information System (INIS)

Takeyama, M.; Liu, C.T.

1989-01-01

The effect of heat treatment on ductility loss in a boron-doped Ni 3 Al was studied by tensile tests of specimens exposed to contaminated environments. Specimens heat treated at 1323 K exhibit only 3.3 pct ductility at 1033 K, whereas a previous study reported a tensile ductility of about 24 pct for specimens heat treated in a high vacuum system. Aluminum oxide and silicon-contaminated regions were observed at and near external surfaces of annealed specimens. The reactions occurring during heat treatment are interpreted in terms of thermodynamics. An Auger electron spectroscopy study revealed oxygen penetration along grain boundaries during annealing. Although the surface oxide layer and silicon contamination both contribute to some reductions in ductility, the major cause for embrittlement comes from oxygen penetration along grain boundaries

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)

Mechanical model for ductility loss

International Nuclear Information System (INIS)

Hu, W.L.

1980-01-01

A mechanical model was constructed to probe into the mechanism of ductility loss. Fracture criterion based on critical localized deformation was undertaken. Two microstructure variables were considered in the model. Namely, the strength ratio of grain boundary affected area to the matrix, Ω, and the linear fraction, x, of grain boundary affected area. A parametrical study was carried out. The study shows that the ductility is very sensitive to those microstructure parameters. The functional dependence of ductility to temperature as well as strain-rate, suggested by the model, is demonstrated to be consistent with the observation

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

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.

Effect of yield stress matching on ductile fracture behavior of girth welds for X line pipe

Energy Technology Data Exchange (ETDEWEB)

Motohashi, Hiroyuki; Hagiwara, Naoto [Tokyo Gas Co., Ltd. (Japan)

2005-07-01

This paper describes the effects of yield stress matching on the ductile fracture behavior of girth welded joints for X linepipes. Three welded joints were made on an X line pipe using several consumables to obtain about a 20% overmatched, even matched and about a 20% under matched weld metal. For these three welded joints, curved wide plate tensile tests were then conducted with a surface notch in the weld metal. To determine the ductile crack initiation from the surface notch, these tests employed a direct-current electric potential (d-c E P) method. Crack opening displacement, gauge length strain and local strain adjacent to the surface notch were also measured. The ductile crack initiation was successfully detected using the d-c E P method. The yield stress matching significantly affected the ductile crack initiation and fracture behavior, that is, the overmatched welded joint had a higher resistance to ductile fracture than that of the under matched welded joint. The allowable strength matching level was determined from the relationship between the strength matching and the gauge length strain at the ductile crack initiation detected using the d-c E P method. (author)

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...

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

Effect of niobium and titanium addition on the hot ductility of boron containing steel

International Nuclear Information System (INIS)

Cho, Kyung Chul; Mun, Dong Jun; Koo, Yang Mo; Lee, Jae Sang

2011-01-01

Research highlights: → Addition of only Nb without Ti has little influence in the hot ductility of B steel. → Hot ductility loss of B-Nb steel is due to grain boundary precipitation of BN. → Adding a small amount of Ti improve the hot ductility of B-Nb steel. → In B-Nb-Ti steel, hot ductility improvement is related to presence of TiN particle. → Presence of TiN particles makes the BN precipitates' distribution more homogeneous. - Abstract: Hot ductility of boron containing steel (B steel) with adding Nb (0.03 wt.%) (B-Nb steel) and B-Nb steel with adding Ti (0.0079 wt.%) (B-Nb-Ti steel) was quantified using hot tensile tests. The specimens were solution-treated at 1350 deg. C and cooled at 20 deg. C s -1 to tensile test temperature (T) in the range of 750 ≤ T ≤ 1050 deg. C. After that, they were strained to failure at a strain rate of 2.5 x 10 -3 s -1 . For the B-Nb steel, severe hot ductility loss was observed at 850 ≤ T ≤ 950 deg. C, which covered the low temperature in which austenite (γ) single-phase exists, and the high temperature at which γ and ferrite (α) coexist. Ductility loss in the B-Nb steel was caused by the presence of a network of BN precipitates, rather than by Nb(C, N) precipitates at the γ grain boundaries. In contrast, hot ductility of the B-Nb-Ti steel was remarkably improved at 850 ≤ T ≤ 950 deg. C. In the B-Nb-Ti steel, BN precipitates preferentially on TiN particles, resulting in increased BN precipitation in the γ grain interior and a decrease in the network of BN precipitates at the γ grain boundaries. These changes reduce strain localization at the γ grain boundaries and therefore increase the hot ductility of the steel.

Development of acceptance criteria and damage tolerance analyzes of the ductile iron insert

International Nuclear Information System (INIS)

Dillstroem, Peter; Alverlind, Lars; Andersson, Magnus

2010-01-01

SKB intends to qualify a test system for detection and sizing of defects deemed to be relevant to the ductile iron insert. In support of this qualification, a damage tolerance analysis indicating the current qualification targets, given assumed damage and failure modes. This report describes the damage tolerance analyzes of different types of defects that are considered relevant of the ductile iron insert. The results are reported separately for each test area (zone) and type of insert (BWRs and PWRs)

Nano-modification to improve the ductility of cementitious composites

International Nuclear Information System (INIS)

Yeşilmen, Seda; Al-Najjar, Yazin; Balav, Mohammad Hatam; Şahmaran, Mustafa; Yıldırım, Gürkan; Lachemi, Mohamed

2015-01-01

Effect of nano-sized mineral additions on ductility of engineered cementitious composites (ECC) containing high volumes of fly ash was investigated at different hydration degrees. Various properties of ECC mixtures with different mineral additions were compared in terms of microstructural properties of matrix, fiber-matrix interface, and fiber surface to assess improvements in ductility. Microstructural characterization was made by measuring pore size distributions through mercury intrusion porosimetry (MIP). Hydration characteristics were assessed using thermogravimetric analysis/differential thermal analysis (TGA/DTA), and fiber-matrix interface and fiber surface characteristics were assessed using scanning electron microscopy (SEM) through a period of 90 days. Moreover, compressive and flexural strength developments were monitored for the same period. Test results confirmed that mineral additions could significantly improve both flexural strength and ductility of ECC, especially at early ages. Cheaper Nano-CaCO 3 was more effective compared to nano-silica. However, the crystal structure of CaCO 3 played a very important role in the range of expected improvements

Experimental and theoretical investigation of column - flat slab joint ductility

International Nuclear Information System (INIS)

Iskhakov, I.; Ribakov, Y.; Shah, A.

2009-01-01

Most modern seismic codes use ductility as one of the basic design parameters. Actually, ductility defines the ability of a structure or its elements to absorb energy by plastic deformations. Until the end of the previous century ductility was defined qualitatively. Most research works related to ductility are focused on structural elements' sections. This study was aimed at complex experimental and theoretical investigation of flat slab-column joints ductility. It is one of the first attempts to obtain quantitative values of joint's ductility for the case of high strength concrete columns and normal strength concrete slabs. It was shown that the flat slab-column joint is a three-dimension (3D) element and its ductility in horizontal and vertical directions are different. This is the main difference between ductility of elements and joint ductility. In case of flat slab-column joints, essential contribution to joint's ductility can be obtained due to the slab's confining effect. Based on experimental data, the authors demonstrate that flat slab-column joint's ductility depends on the joint's confining effect in two horizontal and vertical directions. Furthermore, the influence of slab load intensity and slab reinforcement ratio on the joint's ductility is performed in this study. It is also demonstrated that the effect of the ratio between the slab thickness and the column's section dimension on the ductility parameter is significant. Equations for obtaining a quantitative value of a flat slab-column joint's ductility parameter were developed.

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.

Ductile fracture surface morphology of amorphous metallic alloys

NARCIS (Netherlands)

Miskuf, J; Csach, K; Ocelik, [No Value; Bengus, VZ; Tabachnikova, ED; Duhaj, P; Ocelik, Vaclav

1999-01-01

Fracture surfaces of ductile failure of two types bulk amorphous metallic alloys were studied using quantitative and qualitative fractographic analysis. The observed fractographic behaviour of ductile failure in comparison with the ductile failure of amorphous alloy ribbons shows signs of the same

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......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...

The effects of composition and thermal path on hot ductility of forging steels

Science.gov (United States)

Connolly, Brendan M.

This work examines the effects of composition and thermal path on the hot ductility of several forging steels with varied aluminum and nitrogen content. The primary mechanisms and controlling factors related to hot ductility are identified with a focus on the role of precipitates and segregation. The unique thermal paths and solidification structures of large cross-section forging ingots are discussed. Hot ductility testing is performed in a manner that approximates industrial conditions experienced by large cross-section forging ingots. A computer model for precipitation of aluminum nitride and vanadium nitride in austenite is presented. Industrial material is examined for comparison to experimental findings. It is found that increased aluminum and nitrogen content coarsens the as-solidified structure. The combined effects of microsegregation and uphill diffusion during deformation allow for carbide precipitation at prior austenite grain boundaries which reduces the hot ductility.

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.

Effect of long-term thermal exposure on the hot ductility behavior of GH3535 alloy

International Nuclear Information System (INIS)

Han, F.F.; Zhou, B.M.; Huang, H.F.; Leng, B.; Lu, Y.L.; Li, Z.J.; Zhou, X.T.

2016-01-01

The hot ductility behavior of Ni–16Mo–7Cr alloys (named GH3535) exposed at 700 °C for different durations has been investigated by means of tensile test. It was found that the alloy exhibited a constant low ductility within the first 10 h exposure, and then showed an increasing ductility with the exposure time until 1000 h. After that, the ductility of the alloy decreased gradually with the increasing exposure time up to 10000 h. Detailed microstructural investigations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) have shown that the change in the ductility of the alloy with the exposure time could be attributed to the precipitation of M 12 C carbide at the grain boundary. Such precipitates with size of 200 nm, which are formed during the thermal exposure within 1000 h, can significantly restrain the grain boundary sliding and crack initiation, resulting in the high ductility of the alloy. Further exposure will cause the coarsening of the carbides, making them as the source of grain boundary cracks, hence decreases the ductility of the alloy.

Two brittle ductile transitions in subduction wedges, as revealed by topography

Science.gov (United States)

Thissen, C.; Brandon, M. T.

2013-12-01

Subduction wedges contain two brittle ductile transitions. One transition occurs within the wedge interior, and a second transition occurs along the decollement. The decollement typically has faster strain rates, which suggests that the brittle ductile transition along the decollement will be more rearward (deeper) than the transition within the interior. However, the presence of distinct rheologies or other factors such as pore fluid pressure along the decollement may reverse the order of the brittle-ductile transitions. We adopt a solution by Williams et al., (1994) to invert for these brittle ductile transitions using the wedge surface topography. At present, this model does not include an s point or sediment loading atop the wedge. The Hellenic wedge, however, as exposed in Crete presents an ideal setting to test these ideas. We find that the broad high of the Mediterranean ridge represents the coulomb frictional part of the Hellenic wedge. The rollover in topography north of the ridge results from curvature of the down going plate, creating a negative alpha depression in the vicinity of the Strabo, Pliny, and Ionian 'troughs' south of Crete. A steep topographic rise out of these troughs and subsequent flattening reflects the brittle ductile transition at depth in both the decollement and the wedge interior. Crete exposes the high-pressure viscous core of the wedge, and pressure solution textures provide additional evidence for viscous deformation in the rearward part of the wedge. The location of the decollement brittle ductile transition has been previously poorly constrained, and Crete has never experienced a subduction zone earthquake in recorded history. Williams, C. A., et al., (1994). Effect of the brittle ductile transition on the topography of compressive mountain belts on Earth and Venus. Journal of Geophysical Research Solid Earth

Computer model for ductile fracture

International Nuclear Information System (INIS)

Moran, B.; Reaugh, J. E.

1979-01-01

A computer model is described for predicting ductile fracture initiation and propagation. The computer fracture model is calibrated by simple and notched round-bar tension tests and a precracked compact tension test. The model is used to predict fracture initiation and propagation in a Charpy specimen and compare the results with experiments. The calibrated model provides a correlation between Charpy V-notch (CVN) fracture energy and any measure of fracture toughness, such as J/sub Ic/. A second simpler empirical correlation was obtained using the energy to initiate fracture in the Charpy specimen rather than total energy CVN, and compared the results with the empirical correlation of Rolfe and Novak

Effect of sized and specimen geometry on the initiation and propagation of the ductile fracture

International Nuclear Information System (INIS)

Frund, J.M.; Marini, B.; Bethmont, M.

1994-02-01

Strength to the fracture of the pipe in PWR has to be justified with mechanical analyses. These tests are based on the strength to ductile fracture of steels which are tested in lab. The values of resistance to fracture are obtained through tensile tests on CT specimens (determination of J-R curves). The purpose of this study is to justify the sizes of the specimens which have to be used to characterize the strength to ductile fracture of steel in secondary pipes. Tests were conducted on 0,5T-CT, 1T-CT and 2T-CT specimens. Two materials with different suffer contents were studied. The test results show that the JO,2 values gotten from the different specimens are similar. But the strength to ductile fracture in 2T-CT specimens in lower than the one measured in 0,5t-CT and 1T-CT specimens. The surface of fracture of the different specimens displays splits perpendicular to the notch and parallel to the sheet surface. These splits are produced by the separation of the manganese sulfur inclusions. The effect notes on the J-R curves seems to be relevant to these splits. The reason why these splits might be responsible for a decrease of the tearing modulus are not clearly defined up to this point. The results which have been published show the importance of the geometry effects (presence or not of lateral notches...) and the loading mode on the strength to ductile fracture. We note that the curves determined from tests on CT specimens are conservative. A few preliminary studies showed that the geometry effects on resistance to fracture can be studied and explained by using local approach methods. The Rousselier modeling is useful to explain the behaviour of ferritic steels in ductile fracture. (authors). 20 refs., 7 figs., 5 tabs

Rolling Contact Fatigue Failure Mechanisms of Plasma-Nitrided Ductile Cast Iron

Science.gov (United States)

Wollmann, D.; Soares, G. P. P. P.; Grabarski, M. I.; Weigert, N. B.; Escobar, J. A.; Pintaude, G.; Neves, J. C. K.

2017-05-01

Rolling contact fatigue (RCF) of a nitrided ductile cast iron was investigated. Flat washers machined from a pearlitic ductile cast iron bar were quenched and tempered to maximum hardness, ground, polished and divided into four groups: (1) specimens tested as quenched and tempered; (2) specimens plasma-nitrided for 8 h at 400 °C; (3) specimens plasma-nitrided and submitted to a diffusion process for 16 h at 400 °C; and (4) specimens submitted to a second tempering for 24 h at 400 °C. Hardness profiles, phase analyses and residual stress measurements by x-ray diffraction, surface roughness and scanning electron microscopy were applied to characterize the surfaces at each step of this work. Ball-on-flat washer tests were conducted with a maximum contact pressure of 3.6 GPa, under flood lubrication with a SAE 90 API GL-5 oil at 50 °C. Test ending criterion was the occurrence of a spalling. Weibull analysis was used to characterize RCF's lifetime data. Plasma-nitrided specimens exhibited a shorter RCF lifetime than those just quenched and tempered. The effects of nitriding on the mechanical properties and microstructure of the ductile cast iron are discussed in order to explain the shorter endurance of nitrided samples.

A review on ductile mode cutting of brittle materials

Science.gov (United States)

Antwi, Elijah Kwabena; Liu, Kui; Wang, Hao

2018-06-01

Brittle materials have been widely employed for industrial applications due to their excellent mechanical, optical, physical and chemical properties. But obtaining smooth and damage-free surface on brittle materials by traditional machining methods like grinding, lapping and polishing is very costly and extremely time consuming. Ductile mode cutting is a very promising way to achieve high quality and crack-free surfaces of brittle materials. Thus the study of ductile mode cutting of brittle materials has been attracting more and more efforts. This paper provides an overview of ductile mode cutting of brittle materials including ductile nature and plasticity of brittle materials, cutting mechanism, cutting characteristics, molecular dynamic simulation, critical undeformed chip thickness, brittle-ductile transition, subsurface damage, as well as a detailed discussion of ductile mode cutting enhancement. It is believed that ductile mode cutting of brittle materials could be achieved when both crack-free and no subsurface damage are obtained simultaneously.

Effect of hydriding temperature and strain rate on the ductile-brittle transition in β treated Zircaloy-4

International Nuclear Information System (INIS)

Bai, J.B.

1996-01-01

In this paper, the effect of hydriding temperature and strain rate on the ductile-brittle transition in β treated Zircaloy-4 has been investigated. The hydriding temperature used is 700degC, strain rates being 4x10 -4 s -1 and 4x10 -3 s -1 . The results show that at same conditions the ductility of hydrides decreases as the hydriding temperature decreases. There exists a critical temperature (transition temperature) of 250degC for hydriding at 700degC, below which the hydrided specimens (and so for the hydrides) are brittle, while above it they are ductile. This transition temperature is lower than the one mentioned by various authors obtained for hydriding at 400degC. For the same hydriding temperature of 700degC, the specimens tested at 4x10 -3 s -1 are less ductile than those tested at 4x10 -4 s -1 . Furthermore, unlike at a strain rate of 4x10 -4 s -1 , there is no more a clear ductile-brittle transition behaviour. (author)

Characterizing the influence of matrix ductility on damage phenomenology in continuous fiber-reinforced thermoplastic laminates undergoing quasi-static indentation

KAUST Repository

Yudhanto, Arief

2017-12-12

The use of thermoplastic matrix was known to improve the impact properties of laminated composites. However, different ductility levels can exist in a single family of thermoplastic matrix, and this may consequently modify the damage phenomenology of thermoplastic composites. This paper focuses on the effect of matrix ductility on the out-of-plane properties of thermoplastic composites, which was studied through quasi-static indentation (QSI) test that may represent impact problem albeit the speed difference. We evaluated continuous glass-fiber reinforced polypropylene thermoplastic composites (GFPP), and selected homopolymer PP and copolymer PP that represent ductile and less ductile matrices, respectively. Several cross-ply laminates were selected to study the influence of ply thicknesses and relative orientation of interfaces on QSI properties of GFPP. It is expected that GFPP with ductile matrix improves energy absorption of GFPP. However, the damage mechanism is completely different between GFPP with ductile and GFPP with less ductile matrices. GFPP with ductile matrix exhibits smaller damage zone in comparison to the one with less ductile matrix. Higher matrix ductility inhibits the growth of ply cracking along the fiber, and this causes the limited size of delamination. The stacking sequence poses more influence on less ductile composites rather than the ductile one.

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)

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

Toughening MoSi2 with Niobium metal -- Effects of size and orientation of ductile laminae

International Nuclear Information System (INIS)

Shaw, L.; Abbaschian, R.

1994-01-01

Effects of size and orientation of ductile laminae on the toughness of brittle matrix composites have been evaluated using MoSi 2 composites reinforced with Nb laminae. Nb laminae with thicknesses ranging from 0.127 to 1.0 mm were hot pressed with MoSi 2 powder to prepare the composites. Toughness of the composites was measured using four-point bend test on chevron-notched specimens. It was found that the toughness of the composites increased with increasing size of the niobium laminae. Furthermore, toughening was observed at crack propagation directions perpendicular to the laminae plane, indicating that ductile laminae offer two dimensional toughening. A model based on the bridging contribution of the ductile phase has been proposed to analyze the chevron-notched specimens of the ductile-phase-reinforced brittle matrix composites. The analysis showed that the dependence of the toughness of the composites on the size and orientation of the ductile laminae could be interpreted in terms of their bridging capability and bending contributions

Influence of Copper on the Hot Ductility of 20CrMnTi Steel

Science.gov (United States)

Peng, Hong-bing; Chen, Wei-qing; Chen, Lie; Guo, Dong

2015-02-01

The hot ductility of 20CrMnTi steel with x% copper (x = 0, 0.34) was investigated. Results show that copper can reduce its hot ductility, but there is no significant copper-segregation at the boundary tested by EPMA. The average copper content at grain boundaries and substrate is 0.352% and 0.318% respectively in steel containing 0.34% copper tensile-tested at 950 °C. The fracture morphology was examined with SEM and many small and shallow dimples were found on the fracture of steel with copper, and fine copper sulfide was found from carbon extraction replicas using TEM. Additionally, adding 0.34% copper caused an increase in the dynamic recrystallization temperature from 950 °C to 1000 °C, which indicates that copper can retard the dynamic recrystallization (DRX) of austenite. The detrimental influence of copper on hot ductility of 20CrMnTi steel is due mainly to the fine copper sulfide in the steel and its retarding the DRX.

Ductile Tearing Resistance Indexing of Automotive Grade DP 590 Steel Sheets: EWF Testing Using DENT Specimens

Science.gov (United States)

Sahoo, Subhadra; Padmapriya, N.; De, Partha Sarathi; Chakraborti, P. C.; Ray, S. K.

2018-03-01

The essential work of fracture (EWF) method has been explored for indexing the ductile tearing resistance of DP 590 automotive grade dual-phase steel sheet both in longitudinal (L-T) and transverse (T-L) orientations. The simplest possible test and analysis procedures have been adopted. The EWF method is found to be eminently suitable for routine quality control and product development purposes for such materials. Areas for further research for improving the experimental strategy are highlighted. For the investigated steel sheet, the estimated tearing resistance is found to be distinctly higher for the L-T orientation compared to the T-L orientation; the reason thereof merits further investigation.

Characterization of Austempered Ferritic Ductile Iron

Science.gov (United States)

Dakre, Vinayak S.; Peshwe, D. R.; Pathak, S. U.; Likhite, A. A.

2018-04-01

The ductile iron (DI) has graphite nodules enclose in ferrite envelop in pearlitic matrix. The pearlitic matrix in DI was converted to ferritic matrix through heat treatment. This heat treatment includes austenitization of DI at 900°C for 1h, followed by furnace cooling to 750°C & hold for 1h, then again furnace cooling to 690°C hold for 2h, then samples were allowed to cool in furnace. The new heat treated DI has graphite nodules in ferritic matrix and called as ferritic ductile iron (FDI). Both DIs were austenitized at 900°C for 1h and then quenched into salt bath at 325°C. The samples were soaked in salt bath for 60, 120, 180, 240 and 300 min followed by air cooling. The austempered samples were characterized with help of optical microscopy, SEM and X-ray diffraction analysis. Austempering of ferritic ductile iron resulted in finer ausferrite matrix as compared to ADI. Area fraction of graphite, ferrite and austenite were determining using AXIOVISION-SE64 software. Area fraction of graphite was more in FDI than that of as cast DI. The area fraction of graphite remains unaffected due to austempering heat treatment. Ausferritic matrix coarsened (feathered) with increasing in austempering time for both DI and FDI. Bulk hardness test was carried on Rockwell Hardness Tester with load of 150 kgf and diamond indenter. Hardness obtained in as cast DI is 28 HRC which decreased to 6 HRC in FDI due conversion of pearlitic matrix to ferritic matrix. Hardness is improved by austempering process.

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

Science.gov (United States)

Rajnovic, D; Eric, O; Sidjanin, L

2008-12-01

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

Athermal brittle-to-ductile transition in amorphous solids.

Science.gov (United States)

Dauchot, Olivier; Karmakar, Smarajit; Procaccia, Itamar; Zylberg, Jacques

2011-10-01

Brittle materials exhibit sharp dynamical fractures when meeting Griffith's criterion, whereas ductile materials blunt a sharp crack by plastic responses. Upon continuous pulling, ductile materials exhibit a necking instability that is dominated by a plastic flow. Usually one discusses the brittle to ductile transition as a function of increasing temperature. We introduce an athermal brittle to ductile transition as a function of the cutoff length of the interparticle potential. On the basis of extensive numerical simulations of the response to pulling the material boundaries at a constant speed we offer an explanation of the onset of ductility via the increase in the density of plastic modes as a function of the potential cutoff length. Finally we can resolve an old riddle: In experiments brittle materials can be strained under grip boundary conditions and exhibit a dynamic crack when cut with a sufficiently long initial slot. Mysteriously, in molecular dynamics simulations it appeared that cracks refused to propagate dynamically under grip boundary conditions, and continuous pulling was necessary to achieve fracture. We argue that this mystery is removed when one understands the distinction between brittle and ductile athermal amorphous materials.

Irradiation and inhomogeneity effects on ductility and toughness of (ODS)-7 -13Cr steels

International Nuclear Information System (INIS)

Preininger, D.

2007-01-01

Full text of publication follows: The superimposed effect of irradiation defect and structural inhomogeneity formation on tensile ductility and dynamic toughness of ferritic-martensitic 7-13CrW(Mo)VTa(Nb) and oxide dispersion-strengthened (ODS)-7-13CrWVTa(Ti)- RAFM steels has been examined by work hardening and local stress/strain-induced ductile fracture models. Structural inhomogeneities which strongly promoting plastic instability and localized flow might be formed by the applied fabrication process, high dose irradiation and additionally further during deformation by enhanced local dislocation generation around fine particles or due to slip band formation with localized heating at high impact strain rates ε'. The work hardening model takes into account superimposed dislocation multiplication from stored dislocations, dispersions and also grain boundaries as well as annihilation by cross-slip. Analytical relations have been deduced from the model describing uniform ductility and ductile upper shelf energy (USE) observed from Charpy-impact testes. Especially, the influence of different irradiation defects like atomic clusters, dislocation loops and coherent chromium-rich α'- precipitates have been considered together with effects from strain rate as well as irradiation (TI) and test temperature TT. Strengthening by clusters and more pronounced by dislocation loops formed at higher TI>250 deg. C reduces uniform ductility and also distinctly stronger dynamic toughness USE. A superimposed hardening by the α'- formation in higher Cr containing 9-13Cr steels strongly reduces toughness assisted by a combined grain-boundary embrittlement with reduction of the ductile fracture stress. But that improves work hardening and uniform ductility as observed particularly due to nano-scale Y 2 O 3 - dispersions in ODS-RAFM steels. For ODS- steels additionally the strength-induced reduction of toughness is diminished by a combined microstructural-induced increase of the ductile

Influence of temperature and grain size on the tensile ductility of AISI 316 stainless steel

International Nuclear Information System (INIS)

Mannan, S.L.; Samuel, K.G.; Rodriguez, P.

1985-01-01

The influence of tmeperature and grain size on the tensile ductility of AISI 316 stainless steel has been examined in the temperature range 300-1223 K for specimens with grain sizes varying from 0.025 to 0.650 mm at a nominal strain rate of 3 X 10 -4 s -1 . The percentage total elongation and reduction in area at fracture show minimum ductility at an intermediate temperature, and the temperature corresponding to this ductility minimum has been found to increase with increase in grain size. The total elongation is found to decrease with increase in grain size at high temperatures where failures are essentially intergranular in nature. At 300 K, both uniform and total elongation increase with increase in grain size and then show a small decrease for a very coarse grain size. The high ductility observed at low temperatures (300 K) is consistent with the observation of characteristic dimples associated with transgranular ductile fracture. The ductility minimum with respect to temperature is associated with the occurrence of intergranular fracture, as evidenced by optical and scanning electron microscopy. The present results support the suggestion that the ductility minimum coincides with the maximum amount of grain boundary sliding; at temperatures beyond the ductility minimum, grain boundary separation by cavitation is retarded by the occurrence of grain boundary migration, as evidenced by the grain boundary cusps. In tests conducted at various strain rates in the range 10 -3 -10 -6 s -1 at 873 K the ductility was found to decrease with decreasing strain rate, emphasizing the increased importance of grain boundary sliding at lower strain rates. (Auth.)

Ductility of Ni3Al doped with substitutional elements

International Nuclear Information System (INIS)

Hanada, S.; Chiba, A.; Guo, H.Z.; Watanabe, S.

1993-01-01

This paper reports on ductility of B-free Ni 3 Al alloys. Recrystallized Ni 3 Al binary alloys with Ni-rich compositions show appreciable ductility when an environmental effect is eliminated, while the alloys with stoichiometric and Al-rich compositions remain brittle. The ductility in the Ni-rich Ni 3 Al alloys is associated with low ordering energy. The additions of ternary elements, which are classified as γ formers, ductilize ternary Ni 3 Al alloys(Ni-23 at% Al-2 at% X, X = Pd, Pt, Cu and Co), whereas the additions of γ' formers embrittle ternary Ni 3 Al alloys(Ni-23 at% Al-2 at% X, X = Ta, Mo, Nb, Zr, Hf, V, Ti and Si). The additions of small amounts (less than 1 at%) of γ' formers such as Zr and Hf also ductilize as-cast ternary Ni 3 Al alloys. Ductility of Ni 3 Al alloys doped with substitutional elements is discussed in terms of ordering energy and microstructure

The nucleation of austenite in ferritic ductile cast iron

International Nuclear Information System (INIS)

Chou, J.M.; Hon, M.H.; Lee, J.L.

1992-01-01

Austempered ductile cast iron has recently been receiving increasing attention because of its excellent combination of strength and ductility. Since the austenitization process has a significant influence on the mechanical properties of austempered ductile cast iron, several investigations on the nucleation sites of austenite and diffusion paths of carbon from spheroidal graphite have been reported in ferritic ductile cast iron. However, agreement on this subject has not ben reached. The purpose of this paper is to study the preferential nucleation sites of austenite during austenitization at two austenitizing temperatures in ferritic ductile cast iron. An attempt was made to understand the reasons which give rise to preferential austenite nucleation sites. The carbon diffusion paths from spheroidal graphite were also investigated

Neutron irradiation effects on the ductile-brittle transition of ferritic/martensitic steels

Energy Technology Data Exchange (ETDEWEB)

Klueh, R.L.; Alexander, D.J. [Oak Ridge National Lab., TN (United States)

1997-08-01

Ferritic/martensitic steels such as the conventional 9Cr-1MoVNb (Fe-9Cr-1Mo-0.25V-0.06Nb-0.1C) and 12Cr-1MoVW (Fe-12Cr-1Mo-0.25V-0.5W-0.5Ni-0.2C) steels have been considered potential structural materials for future fusion power plants. The major obstacle to their use is embrittlement caused by neutron irradiation. Observations on this irradiation embrittlement is reviewed. Below 425-450{degrees}C, neutron irradiation hardens the steels. Hardening reduces ductility, but the major effect is an increase in the ductile-brittle transition temperature (DBTT) and a decrease in the upper-shelf energy, as measured by a Charpy impact test. After irradiation, DBTT values can increase to well above room temperature, thus increasing the chances of brittle rather than ductile fracture.

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.

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.

Evaluation of static and dynamic fracture toughness in ductile cast iron

International Nuclear Information System (INIS)

Kobayashi, Toshiro; Yamada, Shinya

1994-01-01

Ductile cast irons have been explored as a cask (container for spent nuclear fuel) material because of their low cost and good formability. The cask, which is a huge casting with 400-mm thickness and 100-Mg weight, envelops the nuclear material. Therefore, the fracture toughness of cask must be evaluated not only under the static loading condition but also under the dynamic loading condition to ensure its safety against an accident during the transport. In this article, crack extension behavior and fracture toughness of ductile cast iron were examined by three-point bend tests, where various detection methods of crack initiation under static and dynamic loading conditions were adopted. Loading on the specimens was interrupted at various displacement points, and the final fracture surfaces of the specimen were observed via scanning electron microscopy (SEM). Crack-tip opening displacement (CTOD) obtained under the dynamic loading conditions was smaller than that under the static loading condition in ferritic ductile cast iron, and CTOD additionally decreased with increasing pearlite content in the matrix. The relationship between J(ΔC) obtained by the compliance changing rate method and J(R) established by the intersection of the crack extension resistance curve and the theoretical blunting line varied with pearlite content. The average value of J(ΔC) and J(R), that is J(mid), was proposed to define the fracture toughness of ductile cast iron; J(mid) was considered to be a reasonable measure for the fracture toughness of ductile cast iron, irrespective of loading condition and the pearlite content in the matrix

Prediction of Ductile Fracture Behaviors for 42CrMo Steel at Elevated Temperatures

Science.gov (United States)

Lin, Y. C.; Liu, Yan-Xing; Liu, Ge; Chen, Ming-Song; Huang, Yuan-Chun

2015-01-01

The ductile fracture behaviors of 42CrMo steel are studied by hot tensile tests with the deformation temperature range of 1123-1373 K and strain rate range of 0.0001-0.1 s-1. Effects of deformation temperature and strain rate on the flow stress and fracture strain of the studied steel are discussed in detail. Based on the experimental results, a ductile damage model is established to describe the combined effects of deformation temperature and strain rate on the ductile fracture behaviors of 42CrMo steel. It is found that the flow stress first increases to a peak value and then decreases, showing an obvious dynamic softening. This is mainly attributed to the dynamic recrystallization and material intrinsic damage during the hot tensile deformation. The established damage model is verified by hot forging experiments and finite element simulations. Comparisons between the predicted and experimental results indicate that the established ductile damage model is capable of predicting the fracture behaviors of 42CrMo steel during hot forging.

EVALUATION OF MACHINABILITY OF DUCTILE IRONS ALLOYED WITH Ni AND Cu IN TERMS OF CUTTING FORCES AND SURFACE QUALITY

Directory of Open Access Journals (Sweden)

Yücel AŞKUN

2003-02-01

Full Text Available Due to the enhanced strength, ductility and thoughness of Ductile Iron (DI when compared to the other types cast iron, its machinability is relatively poor. When a steel part is replaced with ductile iron, however, better machinability is considered to be the most important gain. This study presents the results of machining tests of ductile irons alloyed with Ni and Cu at various contents to determine the effect of their microstructure and mechanical properties on cutting forces and surface roughness. Six different specimen groups of ductile iron alloyed with various amounts of nickel and copper were subjected to machining tests and their machinabilities were investigated based on cutting forces and surface roughness criteria. The results were evaluated according to microstructure and mechanical properties of specimens determined before. In terms of both criterion, the best result obtained was specimen added 0.7 % Ni and 0.7 % Cu. When the specimens were evaluated according to their mechanical properties, the specimens alloyed 1 % Ni and 0.65 % Cu seemed promising.

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.

Friction weld ductility and toughness as influenced by inclusion morphology

International Nuclear Information System (INIS)

Eberhard, B.J.; Schaaf, B.W. Jr.; Wilson, A.D.

1983-01-01

Friction welding consistently provides high strength, freedom from fusion defects, and high productivity. However, friction welds in carbon steel exhibit impact toughness and bend ductility that are significantly lower than that of the base metal. The inclusion content and morphology were suspected to be major contributors to the reduction in weld ductility. For this reason, four electric furnace steels - three types of ASTM A516 Grade 70, and an ASTM A737 Grade B steel - were investigated. Friction welds were made by both the inertia and direct drive process variations and the welds evaluated. It was shown that friction welds of inclusion-controlled steels exhibited much improved toughness and bend ductility were demonstrated. Upper shelf impact energy was equivalent to or greater than that of the base metal in the short transverse direction. The transition temperature range for all four materials was shifted to higher temperatures for both types of friction welds. Under the conditions of this test, the direct drive friction welds showed a greater shift than the inertia friction welds. The ductility and toughness of welds in A737 Grade B steel were superior to welds in A516 Grade 70 steels, reflecting the superior properties of the base metal. Welds of the A737 material had usable Charpy V-notch impact toughness of 20 to 30 ft-lb (27 to 41 J) at temperatures as low as -40 0 F (-40 0 C). All the welds had an acicular structure. The differences in properties between the inertia and direct drive friction welds appear associated with microstructural variations. These variations resulted from the different heat inputs and cooling rates of the two process variations were demonstrated. The beneficial effects of inclusion control on toughness and ductility. In addition, it also indicates that additional improvements may be attainable through control of the as-welded microstructure by process manipulation

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.

Ductility Enhancement of Molybdenum Phase by Nano-sized Oxide Dispersions

Energy Technology Data Exchange (ETDEWEB)

Kang, Bruce

2008-07-18

were evaluated, however, the Mo alloys produced showed little improvement of room-temperature ductility. Finally, toward the end of the research project, a particle mixing process (Hosokawa mechano chemical bonding technology) was applied and the sample Mo alloys showed much improved room-temperature ductility. Follow-up mechanical properties evaluations on the as-processed Mo alloys were carried out using an in-house developed micro-indentation technique which is suitable for in-situ material mechanical properties measurement and ductility/brittle evaluation on small-size sample alloys. Relevant experimental results of the micro-indentation tests are presented.

Estimation scheme for unstable ductile fracture of pressure vessel

International Nuclear Information System (INIS)

Takahashi, Jun; Okamura, Hiroyuki; Sakai, Shinsuke

1990-01-01

This paper presents a new scheme for the estimation of unstable ductile fracture using the J-integral. The proposed method uses a load-versus-displacement diagram which is generated using fully plastic solutions. By this method, the phenomena of the ductile fracture can be grasped visually. Thus, the parametrical survey can be executed far more easily than before. Then, using the proposed method, unstable ductile fracture is analyzed for single-edge cracked plates under both uniform tension and pure bending. In addition, several parametrical surveys are performed concerning (1) J-controlled crack growth, (2) compliance of the structure, (3) ductility of the material (i.e., J-resistance curve), and (4) scale of the structure (i.e., screening criterion). As a result, it is shown that the proposed method is especially effective for the paramtrical study of unstable ductile fracture. (author)

Hot Ductility and Compression Deformation Behavior of TRIP980 at Elevated Temperatures

Science.gov (United States)

Zhang, Mei; Li, Haiyang; Gan, Bin; Zhao, Xue; Yao, Yi; Wang, Li

2018-02-01

The hot ductility tests of a kind of 980 MPa class Fe-0.31C (wt pct) TRIP steel (TRIP980) with the addition of Ti/V/Nb were conducted on a Gleeble-3500 thermomechanical simulator in the temperatures ranging from 873 K to 1573 K (600 °C to 1300 °C) at a constant strain rate of 0.001 s-1. It is found that the hot ductility trough ranges from 873 K to 1123 K (600 °C to 850 °C). The recommended straightening temperatures are from 1173 K to 1523 K (900 °C to 1250 °C). The isothermal hot compression deformation behavior was also studied by means of Gleeble-3500 in the temperatures ranging from 1173 K to 1373 K (900 °C to 1100 °C) at strain rates ranging from 0.01 s-1 to 10 s-1. The results show that the peak stress decreases with the increasing temperature and the decreasing strain rate. The deformation activation energy of the test steel is 436.7 kJ/mol. The hot deformation equation of the steel has been established, and the processing maps have been developed on the basis of experimental data and the principle of dynamic materials model (DMM). By analyzing the processing maps of strains of 0.5, 0.7, and 0.9, it is found that dynamic recrystallization occurs in the peak power dissipation efficiency domain, which is the optimal area of hot working. Finally, the factors influencing hot ductility and thermal activation energy of the test steel were investigated by means of microscopic analysis. It indicates that the additional microalloying elements play important roles both in the loss of hot ductility and in the enormous increase of deformation activation energy for the TRIP980 steel.

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

OpenAIRE

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 inn...

From brittle to ductile fracture in disordered materials.

Science.gov (United States)

Picallo, Clara B; López, Juan M; Zapperi, Stefano; Alava, Mikko J

2010-10-08

We introduce a lattice model able to describe damage and yielding in heterogeneous materials ranging from brittle to ductile ones. Ductile fracture surfaces, obtained when the system breaks once the strain is completely localized, are shown to correspond to minimum energy surfaces. The similarity of the resulting fracture paths to the limits of brittle fracture or minimum energy surfaces is quantified. The model exhibits a smooth transition from brittleness to ductility. The dynamics of yielding exhibits avalanches with a power-law distribution.

Ductility of brazing assemblies with high-temperature materials

International Nuclear Information System (INIS)

Colbus, J.; De Paoli, A.

1977-01-01

Brazing assemblies with the high temperature materials X8CrNiNb1613, X12CrNiMo12 and X8NiCrAlTiMo7020 have been produced using different solder metals. These brazing assemblies have been studied with the emphasis on the interrelation between microstructure and ductility. Besides the ordinary impact bend tests of notched and unnotched brazed joints, the impact bend tests of unnotched brazed joints with drawing of a Strength-Way-Diagram have been added for better results. (GSC) [de

Influence of strain-rate on the flow stress and ductility of copper and tantalum

International Nuclear Information System (INIS)

Regazzoni, G.; Montheillet, F.; Dormeval, R.; Stelly, M.

1981-09-01

Tensile experiments were carried out at strain-rates in a range from epsilon = 6.10 -5 to 3.10 3 s -1 at 293 K and 673 K or 773 K. Two types of copper (FCC) and pure tantalum (BCC) were tested. The variations of ductility have been investigated in relation with the σ - epsilon equations of the materials and the examinations of fracture surfaces. They can be explained in terms of stability and intrinsic ductility

Characterization of molybdenum particles reinforced Al6082 aluminum matrix composites with improved ductility produced using friction stir processing

Energy Technology Data Exchange (ETDEWEB)

Selvakumar, S., E-mail: lathaselvam1963@gmail.com [Department of Mechanical Engineering, Nehru Institute of Technology, Coimbatore 641105, Tamil Nadu (India); Department of Mechanical Engineering, Anna University, Chennai 600025, Tamil Nadu (India); Dinaharan, I., E-mail: dinaweld2009@gmail.com [Department of Mechanical Engineering Science, University of Johannesburg, Auckland Park Kingsway Campus, Johannesburg 2006 (South Africa); Palanivel, R., E-mail: rpalanivelme@gmail.com [Department of Mechanical Engineering Science, University of Johannesburg, Auckland Park Kingsway Campus, Johannesburg 2006 (South Africa); Ganesh Babu, B., E-mail: profbgb@gmail.com [Department of Mechanical Engineering, Roever College of Engineering and Technology, Perambalur 621212, Tamil Nadu (India)

2017-03-15

Aluminum matrix composites (AMCs) reinforced with various ceramic particles suffer a loss in ductility. Hard metallic particles can be used as reinforcement to improve ductility. The present investigation focuses on using molybdenum (Mo) as potential reinforcement for Mo(0,6,12 and 18 vol.%)/6082Al AMCs produced using friction stir processing (FSP). Mo particles were successfully retained in the aluminum matrix in its elemental form without any interfacial reaction. A homogenous distribution of Mo particles in the composite was achieved. The distribution was independent upon the region within the stir zone. The grains in the composites were refined considerably due to dynamic recrystallization and pinning effect. The tensile test results showed that Mo particles improved the strength of the composite without compromising on ductility. The fracture surfaces of the composites were characterized with deeply developed dimples confirming appreciable ductility. - Highlights: •Molybdenum particles used as reinforcement for aluminum composites to improve ductility. •Molybdenum particles were retained in elemental form without interfacial reaction. •Homogeneous dispersion of molybdenum particles were observed in the composite. •Molybdenum particles improved tensile strength without major loss in ductility. •Deeply developed dimples on the fracture surfaces confirmed improved ductility.

Characterization of molybdenum particles reinforced Al6082 aluminum matrix composites with improved ductility produced using friction stir processing

International Nuclear Information System (INIS)

Selvakumar, S.; Dinaharan, I.; Palanivel, R.; Ganesh Babu, B.

2017-01-01

Aluminum matrix composites (AMCs) reinforced with various ceramic particles suffer a loss in ductility. Hard metallic particles can be used as reinforcement to improve ductility. The present investigation focuses on using molybdenum (Mo) as potential reinforcement for Mo(0,6,12 and 18 vol.%)/6082Al AMCs produced using friction stir processing (FSP). Mo particles were successfully retained in the aluminum matrix in its elemental form without any interfacial reaction. A homogenous distribution of Mo particles in the composite was achieved. The distribution was independent upon the region within the stir zone. The grains in the composites were refined considerably due to dynamic recrystallization and pinning effect. The tensile test results showed that Mo particles improved the strength of the composite without compromising on ductility. The fracture surfaces of the composites were characterized with deeply developed dimples confirming appreciable ductility. - Highlights: •Molybdenum particles used as reinforcement for aluminum composites to improve ductility. •Molybdenum particles were retained in elemental form without interfacial reaction. •Homogeneous dispersion of molybdenum particles were observed in the composite. •Molybdenum particles improved tensile strength without major loss in ductility. •Deeply developed dimples on the fracture surfaces confirmed improved ductility.

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...

Ductile mandrel and parting compound facilitate tube drawing

Science.gov (United States)

Burt, W. R., Jr.; Mayfield, R. M.; Polakowski, N. H.

1966-01-01

Refractory tubing is warm drawn over a solid ductile mandrel with a powder parting compound packed between mandrel and the tubes inner surface. This method applies also to the coextrusion of a billet and a ductile mandrel.

Ductile-regime turning of germanium and silicon

Science.gov (United States)

Blake, Peter N.; Scattergood, Ronald O.

1989-01-01

Single-point diamond turning of silicon and germanium was investigated in order to clarify the role of cutting depth in coaxing a ductile chip formation in normally brittle substances. Experiments based on the rapid withdrawal of the tool from the workpiece have shown that microfracture damage is a function of the effective depth of cut (as opposed to the nominal cutting depth). In essence, damage created by the leading edge of the tool is removed several revolutions later by lower sections of the tool edge, where the effective cutting depth is less. It appears that a truly ductile cutting response can be achieved only when the effective cutting depth, or critical chip thickness, is less than about 20 nm. Factors such as tool rake angle are significant in that they will affect the actual value of the critical chip thickness for transition from brittle to ductile response. It is concluded that the critical chip thickness is an excellent parameter for measuring the effects of machining conditions on the ductility of the cut and for designing tool-workpiece geometry in both turning and grinding.

System Reliability of Timber Structures with Ductile Behaviour

DEFF Research Database (Denmark)

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

2011-01-01

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....... 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...

Hot ductility and flow stress of AISI 4130 and 52100-type steels

Energy Technology Data Exchange (ETDEWEB)

Barbier, Damien [Vallourec Research Center France, F-59620 Aulnoye-Aymeries (France); Guérin, Jean-Dominique, E-mail: jean-dominique.guerin@univ-valenciennes.fr [UVHC, LAMIH UMR CNRS 8201, F-59313 Valenciennes (France); Univ Lille Nord de France, F-59000 Lille (France); Dubar, Mirentxu [UVHC, LAMIH UMR CNRS 8201, F-59313 Valenciennes (France); Univ Lille Nord de France, F-59000 Lille (France); Bénard, Thierry; Bonneau, Sébastien [Vallourec Research Center France, F-59620 Aulnoye-Aymeries (France); Cabrera, Eli Saùl Puchi [School of Metallurgical Engineering and Materials Science, Universidad Central de Venezuela (Venezuela, Bolivarian Republic of)

2017-04-06

The present communication reports the main findings of an investigation that has been conducted in order to examine the ductility of both the AISI 4130 and 52100 steel grades, in a wide range of temperatures, spanning from room temperature up to 1250 °C, deformed in tension at strain rates of approximately 0.005 s{sup −1}. The ductility of the investigated alloys has been determined employing two different methodologies. The first one is based on the classical definition of this property, as determined from the reduction in the cross sectional area of the tensile specimen after fracture. The second method, which is proposed in this work, is based on the measurement of the energy under the engineering stress-strain curve and the decomposition of the total deformation energy into the uniform plastic and non-uniform or fracture energy components. Complementary axisymmetric compression tests have also been carried out in the temperature range of 600 °Cto 900 °C, in order to determine the strain related to the onset of dynamic recrystallization (DRX) at temperatures above 800 °C, as well as the strain corresponding to the occurrence of necking at these temperatures. The ductility values determined from both methods are observed to increase from approximately 10–80% when the testing temperature increases from room temperature to 1200 °C. Both measurements are also observed to agree up to temperatures of about 600 °C. Also, it has been determined that above this temperature, the ductility values derived from the energy criterion are somewhat higher than those computed from the reduction in the cross section area of the specimens. It has been shown that the onset of DRX gives rise to an improvement in the ductility of both steels, which is also related to a significant increase in the strain for the beginning of necking. The advantage of the energy criterion, in comparison with that based on the area reduction after fracture, is discussed.

On the notch ductility of a magnesium-rare earth alloy

Energy Technology Data Exchange (ETDEWEB)

Kondori, B., E-mail: bkondori.13034@tamu.edu [Department of Materials Science & Engineering, Texas A& M University, College Station, TX 77843 (United States); Benzerga, A.A. [Department of Materials Science & Engineering, Texas A& M University, College Station, TX 77843 (United States); Department of Aerospace Engineering, Texas A& M University, College Station, TX 77843 (United States)

2015-10-28

The room-temperature notch ductility of magnesium-rare earth alloy WE43 is investigated for two loading orientations. This material is endowed with quasi-isotropic plastic flow properties, higher strength and similar uniaxial ductility in comparison with other commercially available Mg alloys. The authors have recently shown that the notch ductility of a Mg–Al–Zn alloy is greater than its uniaxial ductility over a wide range of notch geometries. This paper investigates whether the same trends hold for WE43, discusses the orientation dependence of ductility and the propensity for intergranular fracture at high levels of hydrostatic tension. The latter mode of fracture is analyzed by means of detailed fractography in order to elucidate the role of grain-boundary particles and precipitates in the fracture process.

Enhanced hot ductility of a Cr–Mo low alloy steel by rare earth cerium

International Nuclear Information System (INIS)

Jiang, X.; Song, S.-H.

2014-01-01

The hot ductility of a 1Cr–0.5Mo low alloy steel is investigated over a temperature range of 700–1050 °C using a Gleeble thermomechanical simulator in conjunction with various characterization techniques. The steel samples undoped and doped with cerium are heated at 1300 °C for 3 min and then cooled with a rate of 5 K s −1 down to different test temperatures, followed by tensile deformation until fracture. The results show that the hot ductility of the steel, evaluated by the reduction in area, can be substantially enhanced by a minor addition of cerium, especially in the range 800–1000 °C. In the austenite–ferrite dual-phase region, cerium may delay the formation of proeutectoid ferrite layers along austenite grain boundaries, thereby increasing the hot ductility of the steel. In the single austenite region, grain boundary segregation of cerium may increase the grain boundary cohesion, toughening the steel and thus raising the resistance to grain boundary sliding as well as promoting dynamic recrystallization. Consequently, the hot ductility of the steel is enhanced

On key factors influencing ductile fractures of dual phase (DP) steels

International Nuclear Information System (INIS)

Sun, X.; Choi, K.S.; Soulami, A.; Liu, W.N.; Khaleel, M.A.

2009-01-01

In this paper, we examine the key factors influencing ductile failure of various grades of dual phase (DP) steels using the microstructure-based modeling approach. Various microstructure-based finite element models are generated based on the actual microstructures of DP steels with different martensite volume fractions. These models are, then, used to investigate the influence of ductility of the constituent ferrite phase and also the influence of voids introduced in the ferrite phase on the overall ductility of DP steels. It is found that with volume fraction of martensite in the microstructure less than 15%, the overall ductility of the DP steels strongly depends on the ductility of the ferrite matrix, hence pre-existing micro-voids in the microstructure significantly reduce the overall ductility of the steel. When the volume fraction of martensite is above 15%, the pre-existing voids in the ferrite matrix does not significantly reduce the overall ductility of the DP steels, and the overall ductility is more influenced by the mechanical property disparity between the two phases. The applicability of the phase inhomogeneity driven ductile failure of DP steels is then discussed based on the obtained computational results for various grades of DP steels, and the experimentally obtained scanning electron microscopy (SEM) pictures of the corresponding grades of DP steels near fracture surface are used as evidence for result validations.

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)

Influence of mean stress on fatigue strength of ferritic-pearlite ductile cast iron with small defects

Science.gov (United States)

Deguchi, T.; Kim, H. J.; Ikeda, T.; Yanase, K.

2017-05-01

Because of their excellent mechanical properties, low cost and good workability, the application of ductile cast iron has been increased in various industries such as the automotive, construction and rail industries. For safety designing of the ductile cast iron component, it is necessary to understand the effect of stress ratio, R, on fatigue limit of ductile cast iron in the presence of small defects. Correspondingly in this study, rotating bending fatigue tests at R = -1 and tension-compression fatigue tests at R = -1 and 0.1 were performed by using a ferritic-pearlitic ductile cast iron. To study the effects of small defects, we introduced a small drilled hole at surface of a specimen. The diameter and depth of a drilled hole were 50, 200 and 500 μm, respectively. The non-propagating cracks emanating from graphite particles and holes edge were observed at fatigue limit, irrespective of the value of stress ratio. From the microscopic observation of crack propagation behavior, it can be concluded that the fatigue limit is determined by the threshold condition for propagation of a small crack. It was found that the effect of stress ratio on the fatigue limit of ductile cast iron with small defects can be successfully predicted based on \\sqrt {area} parameter model. Furthermore, a use of the tensile strength, σ B, instead of the Vickers hardness, HV, is effective for fatigue limit prediction.

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.

The “ductility exhaustion” method for static strength assessment of fusion structures

Energy Technology Data Exchange (ETDEWEB)

Thompson, Vaughan, E-mail: vaughan.thompson@ccfe.ac.uk; Vizvary, Zsolt

2015-10-15

Graphical abstract: - Highlights: • Reduced conservatism and more complex geometry. • Assessment process simplified. • Gives insight into real material behaviour – virtual proof test. • Leads onto structural failure modelling. • Ductility exhaustion and global plastic collapse structural assessment. - Abstract: The traditional method for static strength assessment of structures uses elastic stresses computed along critical ligaments and then divided into categories depending on their nature e.g. bending/membrane and primary/secondary. More recently, highly realistic plastic simulations are possible using FE (finite elements) which offer useful advantages over the traditional approach including (a) more accurate modelling of complex geometries, (b) a more straightforward assessment process and (c) a less conservative approach. The plastic analysis must consider both global and local effects, and the paper looks in detail at the “ductility exhaustion” method for the latter. Simple test cases show how the method can be applied in both the Abaqus and ANSYS FE Codes and for the case of a JET beryllium tile, the method has improved reserve factors for disruption loads considerably to the point where the lower operating temperature can be safely lowered from 200 °C to 100 °C where the low ductility of beryllium is an issue.

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)

Effects of chemical composition and test parameters on the hot ductility of C-Mn-Al steels; Efeito da composicao quimica e parametros de ensaios sobre a ductilidade a quente de acos C-Mn-Al

Energy Technology Data Exchange (ETDEWEB)

Macedo, Marcelo C.S. de; Comineli, Osvaldo G; Pancieri, Jose G.P.; Oliveira, Maria A.L. de [Espirito Santo Univ., Vitoria, ES (Brazil). Dept. de Engenharia Mecanica; Souza Lima Cardoso, Geraldo I. de [Companhia Siderurgica de Tubarao (CST), Serra, ES (Brazil); Mintz, Barry [The City Univ., London (United Kingdom)

1987-12-31

The effects of Al content, as well as hot tensile test parameters on hot ductility of two C-Mn-Al steels are presented. Thermal cycle were carried out to study the influence of thermal oscillations during those compositions cooling, consisting of heating the samples up to a solubilization temperature, high enough to dissolve any phase which could possibly be present in the original ingot, and also to produce a coarser grain size. After 5 minutes at 1330 deg C, the steels were cooled in three different ways to reach test temperature and samples remain at this temperature for 5 minutes for stabilization before testing. Further, a preliminary comparison between hot ductility results, obtained when samples are molten and continuously cooled at two different rates, and those obtained for solution treated samples which are cooled at an intermediate cooling rate. For the two composition solution treated, a ductility was observed trough displaced from each other about 50 deg C, being the Al content the responsible for this difference. (author) 14 refs., 11 figs., 1 tab.

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.

Ductile alloy and process for preparing composite superconducting wire

Science.gov (United States)

Verhoeven, J.D.; Finnemore, D.K.; Gibson, E.D.; Ostenson, J.E.

An alloy for the commercial production of ductile superconducting wire is prepared by melting together copper and at least 15 weight percent niobium under non-oxygen-contaminating conditions, and rapidly cooling the melt to form a ductile composite consisting of discrete, randomly distributed and oriented dendritic-shaped particles of niobium in a copper matrix. As the wire is worked, the dendritic particles are realigned parallel to the longitudinal axis and when drawn form a plurality of very fine ductile superconductors in a ductile copper matrix. The drawn wire may be tin coated and wound into magnets or the like before diffusing the tin into the wire to react with the niobium. Impurities such as aluminum or gallium may be added to improve upper critical field characteristics.

Hot Ductility Behaviors in the Weld Heat-Affected Zone of Nitrogen-Alloyed Fe-18Cr-10Mn Austenitic Stainless Steels

Science.gov (United States)

Moon, Joonoh; Lee, Tae-Ho; Hong, Hyun-Uk

2015-04-01

Hot ductility behaviors in the weld heat-affected zone (HAZ) of nitrogen-alloyed Fe-18Cr-10Mn austenitic stainless steels with different nitrogen contents were evaluated through hot tension tests using Gleeble simulator. The results of Gleeble simulations indicated that hot ductility in the HAZs deteriorated due to the formation of δ-ferrite and intergranular Cr2N particles. In addition, the amount of hot ductility degradation was strongly affected by the fraction of δ-ferrite.

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.

Brittle-to-Ductile Transition in Metallic Glass Nanowires.

Science.gov (United States)

Şopu, D; Foroughi, A; Stoica, M; Eckert, J

2016-07-13

When reducing the size of metallic glass samples down to the nanoscale regime, experimental studies on the plasticity under uniaxial tension show a wide range of failure modes ranging from brittle to ductile ones. Simulations on the deformation behavior of nanoscaled metallic glasses report an unusual extended strain softening and are not able to reproduce the brittle-like fracture deformation as found in experiments. Using large-scale molecular dynamics simulations we provide an atomistic understanding of the deformation mechanisms of metallic glass nanowires and differentiate the extrinsic size effects and aspect ratio contribution to plasticity. A model for predicting the critical nanowire aspect ratio for the ductile-to-brittle transition is developed. Furthermore, the structure of brittle nanowires can be tuned to a softer phase characterized by a defective short-range order and an excess free volume upon systematic structural rejuvenation, leading to enhanced tensile ductility. The presented results shed light on the fundamental deformation mechanisms of nanoscaled metallic glasses and demarcate ductile and catastrophic failure.

Determination of Ductile Tearing Resistance Curve in Weld Joints

International Nuclear Information System (INIS)

Marie, S.; Gilles, P.; Ould, P.

2010-01-01

Steels present in the ductile domain a tearing resistance which increase with the crack propagation up to the failure. This ductile tearing resistance is in general characterised with curves giving the variation of a global parameter (opening displacement at the crack tip delta, integral J) versus the crack extension Delta a. These global approaches depend more or less on the specimen geometry and on the type of the imposed loading. Local approaches based on the description of the ductile tearing mechanisms provide reliable solution to the transferability problem (from the lab specimen to the component) but are complex and costly to use and are not codified. These problems get worse in the case of a weld joint where no standard is available for the measurement of their ductile tearing resistance. But the welded joints are often the weak point of the structure because of greater risk of defects, the heterogeneity of the microstructure of the weld, deformation along the interface between two materials with different yield stress (mismatch).... After briefly recalling the problems of transferability of the ductile tearing resistance curves obtained on lab specimen to the case of components, this article identifies the factors complicating the determination of the toughness in the welded joints and gives recommendations for the experimental determination of ductile tearing resistance curves of welded joints

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

Ductility in hot isostatically pressed 250-grade maraging steel

International Nuclear Information System (INIS)

German, R.M.; Smugeresky, J.E.

1978-01-01

Prealloyed 250-grade maraging steel powder produced by the rotating electrode process was fully consolidated by hot isostatic pressing (HIP) at 1100 and 1200 0 C. The strength following aging (3 h at 480 0 C) equalled that of wrought material; however, ductility was negligible. This lack of ductility in the powder metallurgy product was traced to titanium segregation which occurred at the powder surface during power production. The formation of a titanium intermetallic at the prior particle boundaries during aging caused failure at low plastic strains. Altered aging treatments successfully broke up the embrittling film and resulted in a significant ductility recovery for the HIP material. Analysis of the fracture process indicates that further ductility gains are possible by reducing the titanium content, refining the particle size, and optimizing the thermal cycles

Irradiation effects on tensile ductility and dynamic toughness of ferritic-martensitic 7-12 Cr steels

International Nuclear Information System (INIS)

Preininger, D.

2006-01-01

The superimposed effect of irradiation-induced hardening by small defects (clusters, dislocation loops) and chromium-rich - precipitate formations on tensile ductility and Charpy-impact behaviour of various ferritic-martensitic (7-13)CrWVTa(Ti)-RAFM steels have been examined by micro-mechanical deformation and ductile/dynamic fracture models. Analytical relations have been deduced describing irradiation-induced changes of uniform ductility and fracture strain as well as ductile-to-brittle transition temperature DBTT and ductile upper shelf energy USE observed from impact tests. The models apply work-hardening with competitive action of relevant dislocation multiplication and annihilation reactions. The impact model takes into account stress intensity with local plasticity and fracture within the damage zone of main crack. Especially, the influences of radiation-induced changes in ductile and dynamic fracture stresses have been considered together with effects from strain rate sensitivity of strength, precipitate morphology as mean size dp and volume fraction fv as well as deformation temperature and strain rate. For these, particularly the correlation between tensile ductility and impact properties have been examined. Strengthening by clusters and loops generally reduces uniform ductility, and more stronger fracture strain as well as ductile upper shelf energy USE and additionally increases DBTT for constant fracture stresses. A superimposed precipitation hardening by formation of 3-6 nm, f v 6 nm, which clear above the sharable limit of coherent precipitates increases with increasing fraction fv and but strongly reduces with increasing matrix strength due to full martensitic structure, higher C, N alloying contents and pronounced hardening by irradiation-induced cluster and loop formations. A combined increase of fracture stresses due to irradiation-induced changes of the grain boundary structure diminishes the strength-induced increase in DBTT and more stronger

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.

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.

Effect of the hydrogen concentration on the ductility of Zry-4

International Nuclear Information System (INIS)

Domizzi, G.; Ovejero Garcia, J.

1996-01-01

After many years in service, zirconium alloys employed in nuclear reactors may reach high contents of hydride particles, exceeding the hydrogen solid solubility at the service temperature. The brittle character of zirconium hydride promotes the alloy embrittlement. In order to predict the critical hydrogen concentration which causes a ductile-brittle transition in a Zry-4 foil, 0.02mm thick, tensile test specimens were hydride by gaseous charging. To obtain uniform hydride distribution the specimens were electroplated with a film of copper prior to gaseous charge. In absence of oxide film, the foils retained its ductility up to high hydrogen concentration (950 Og/g). The critical hydrogen concentration was attained at 2900-3100 Og/g. (author). 4 refs., 2 figs., 1 tab

Hot ductility behavior of a low carbon advanced high strength steel (AHSS) microalloyed with boron

OpenAIRE

Mejía, Ignacio; Bedolla Jacuinde, Arnoldo; Maldonado, Cuauhtémoc; Cabrera Marrero, José M.

2011-01-01

The current study analyses the influence of boron addition on the hot ductility of a low carbon advanced high strength NiCrVCu steel. For this purpose hot tensile tests were carried out at different temperatures (650, 750, 800, 900 and 1000 ◦C) at a constant true strain rate of 0.001 s−1. Experimental results showed a substantial improvement in hot ductility for the low carbon advanced high strength steel when microalloyed with boron compared with that without boron addition. Nevertheless,...

Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock

Science.gov (United States)

Wenning, Quinn C.; Madonna, Claudio; de Haller, Antoine; Burg, Jean-Pierre

2018-05-01

This study characterizes the elastic and fluid flow properties systematically across a ductile-brittle fault zone in crystalline rock at the Grimsel Test Site underground research laboratory. Anisotropic seismic velocities and permeability measured every 0.1 m in the 0.7 m across the transition zone from the host Grimsel granodiorite to the mylonitic core show that foliation-parallel P- and S-wave velocities systematically increase from the host rock towards the mylonitic core, while permeability is reduced nearest to the mylonitic core. The results suggest that although brittle deformation has persisted in the recent evolution, antecedent ductile fabric continues to control the matrix elastic and fluid flow properties outside the mylonitic core. The juxtaposition of the ductile strain zone next to the brittle zone, which is bounded inside the two mylonitic cores, causes a significant elastic, mechanical, and fluid flow heterogeneity, which has important implications for crustal deformation and fluid flow and for the exploitation and use of geothermal energy and geologic waste storage. The results illustrate how physical characteristics of faults in crystalline rocks change in fault zones during the ductile to brittle transitions.

Brittle versus ductile behaviour of nanotwinned copper: A molecular dynamics study

International Nuclear Information System (INIS)

Pei, Linqing; Lu, Cheng; Zhao, Xing; Zhang, Liang; Cheng, Kuiyu; Michal, Guillaume; Tieu, Kiet

2015-01-01

Nanotwinned copper (Cu) exhibits an unusual combination of ultra-high yield strength and high ductility. A brittle-to-ductile transition was previously experimentally observed in nanotwinned Cu despite Cu being an intrinsically ductile metal. However, the atomic mechanisms responsible for brittle fracture and ductile fracture in nanotwinned Cu are still not clear. In this study, molecular dynamics (MD) simulations at different temperatures have been performed to investigate the fracture behaviour of a nanotwinned Cu specimen with a single-edge-notched crack whose surface coincides with a twin boundary. Three temperature ranges are identified, indicative of distinct fracture regimes, under tensile straining perpendicular to the twin boundary. Below 1.1 K, the crack propagates in a brittle fashion. Between 2 K and 30 K a dynamic brittle-to-ductile transition is observed. Above 40 K the crack propagates in a ductile mode. A detailed analysis has been carried out to understand the atomic fracture mechanism in each fracture regime

A diffraction based study of the deformation mechanisms in anomalously ductile B2 intermetallics

Science.gov (United States)

Mulay, Rupalee Prashant

For many decades, the brittle nature of most intermetallic compounds (e.g. NiAl) has been the limiting factor in their practical application. Many B2 (CsCl prototypical structure) intermetallics are known to exhibit slip on the {110} slip mode, which provides only 3 independent slip systems and, hence, is unable to satisfy the von Mises (a.k.a. Taylor) criterion for polycrystalline ductility. As a result, inherent polycrystalline ductility is unexpected. Recent discovery of a number of ductile B2 intermetallics has raised questions about possible violation of the von Mises criterion by these alloys. These ductile intermetallic compounds are MR (metal (M) combined with a rare earth metal or group IV refractory metal (R)) alloys and are stoichiometric, ordered compounds. Single crystal slip trace analyses have only identified the presence of {011} or {010} slip systems. More than 100 other B2 MR compounds are known to exist and many of them have already been shown to be ductile (e.g., CuY, AgY, CuDy, CoZr, CoTi, etc.). Furthermore, these alloys exhibit a large Bauschinger effect. The present work uses several diffraction based techniques including electron back scattered diffraction (EBSD), X-ray diffraction (XRD) and in-situ neutron diffraction; in conjunction with scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical testing, and crystal plasticity modeling, to elucidate the reason for ductility in select B2 alloys, explore the spread of this ductility over the B2 family, and understand the Bauschinger effect in these alloys. Several possible explanations (e.g., slip of dislocations, strong texture, phase transformations and twinning) for the anomalous ductility were explored. An X-ray diffraction based analysis ruled out texture, phase purity and departure from order as explanations for the anomalous ductility in MR alloys. In-situ neutron diffraction and post deformation SEM, EBSD, and TEM were unable to detect any evidence for

Influence of the surface roughness on the fatigue properties in ausferritic ductile irons (ADI

Directory of Open Access Journals (Sweden)

Svenningsson Roger

2014-06-01

Full Text Available Heat treatment of cast ductile iron (DI to ausferritic ductile iron (ADI is known to increase fatigue properties. However, the surface roughness of the cast material is also of significant importance. In this investigation, test rods with seven different surface qualities were cast from the same melt i.e. with same chemical composition. The surfaces of the test rods were varied by a number of parameters; grain size of the moulding sand, coated or non-coated mould surfaces, as-cast or machined and polished, shot peened or not. In addition, a reference material in conventional DI was cast and tested. All eight series were subjected to high-cycle fatigue bending tests. The results show that surface defects, such as micro porosity and minor inclusions drastically decrease the fatigue properties. For some ADI materials the stress amplitude limit was actually lower compared to the non-heat treated DI. The machined, polished and shot-peened material demonstrated the best fatigue properties, which is as expected.

A study on the effects of artifacts on fatigue limit of ductile cast iron with ferritic structure

International Nuclear Information System (INIS)

Kim, Jin Hak; Kim, Min Gun

2000-01-01

In this study, fatigue tests were performed to examine the effects of micro drill hole on fatigue limit of as cast and Austempered Ductile cast Iron (ADI) using the rotary bending fatigue tester. As results, micro drill holes (diameter≤0.4mm) did not influence the fatigue limit of ADI, compared to annealed ductile cast iron; the critical defect size of crack initiation, in ADI was larger than as cast. If the √areas of micro drill hole and graphite nodule in ADI are comparable, crack initiates at the graphite nodule. When the ruggedness develops through austempering treatment process, microstructure on crack initiation at micro drill hole is tougher than that of as cast ductile cast iron

Effect of silicon content and defects on the lifetime of ductile cast iron

Directory of Open Access Journals (Sweden)

Alhussein Akram

2014-06-01

Full Text Available In this work, the influence of microstructure on the mechanical properties has been studied for different grades of ferritic ductile cast iron. Mechanical tests were carried out and the effect of silicon on the resistance of material was well noticed. An increasing silicon content increases the strength and decreases the ductility of material. The lifetime and endurance limit of material were affected by the presence of defects in material and microstructure heterogeneity. Metallurgical characterizations showed that the silicon was highly segregated around graphite nodules which leads to the initiation of cracks. The presence of defects causes the stress concentration and leads to the initiation and propagation of cracks.

Relationship between Microstructure and Ductility Dip Cracking resistance of Alloy 600/690 weld metals

Energy Technology Data Exchange (ETDEWEB)

Ryu, Jae Yong; Lee, Chang Hee [Hanyang University, Seoul (Korea, Republic of); Kim, Min Chul; Lee, Ho Jin; Kim, Keoung Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Kwang Soo; Shim, Deog Nam [Doosan HEAVY Industries and Construction, Seoul (Korea, Republic of)

2009-10-15

Ni-Cr-Fe alloys are used extensively in nuclear power systems for their resistance to general corrosion, localized corrosion, and environmentally assisted cracking. However, concerns with stress corrosion cracking of moderate chromium (14.22 wt-%) alloys such as Alloy 600 and its filler metals(FMs) (E-182 and EN82) have driven the application of higher chromium (28.30 wt-%) alloys like Alloy 690. While Alloy 690 and its FMs show outstanding resistance to environmentally assisted cracking in most water-reactor environments, these alloys are prone to welding defects, most notably to ductility dip cracking(DDC). The DDC occurs at temperatures between 0.5 and 0.8 of their melting temperature. This ductility drop may result in intergranular elevated temperature cracking often referred to as DDC. The DDC may occur during the high temperature processing of these alloys or during welding if the imposed strain exhausts the available ductility within this temperature range. Several alloy systems including Ni-base alloys, Ni.Cu alloys, Cu alloys, stainless steels and steels, have been reported to be susceptible to DDC. A complete understanding of the DDC mechanism does not exist, which makes DDC control in actual production conditions a very difficult task. In this study, the DDC resistance was evaluated with different FMs which have different chemical composition. The microstructural features of FMs such as precipitation behavior and grain boundaries morphology were observed, and it were correlated with the DDC susceptibility. The hot ductility test and strainto- fracture test was used to evaluate the DDC susceptibility at high temperature.

Relationship between Microstructure and Ductility Dip Cracking resistance of Alloy 600/690 weld metals

International Nuclear Information System (INIS)

Ryu, Jae Yong; Lee, Chang Hee; Kim, Min Chul; Lee, Ho Jin; Kim, Keoung Ho; Park, Kwang Soo; Shim, Deog Nam

2009-01-01

Ni-Cr-Fe alloys are used extensively in nuclear power systems for their resistance to general corrosion, localized corrosion, and environmentally assisted cracking. However, concerns with stress corrosion cracking of moderate chromium (14.22 wt-%) alloys such as Alloy 600 and its filler metals(FMs) (E-182 and EN82) have driven the application of higher chromium (28.30 wt-%) alloys like Alloy 690. While Alloy 690 and its FMs show outstanding resistance to environmentally assisted cracking in most water-reactor environments, these alloys are prone to welding defects, most notably to ductility dip cracking(DDC). The DDC occurs at temperatures between 0.5 and 0.8 of their melting temperature. This ductility drop may result in intergranular elevated temperature cracking often referred to as DDC. The DDC may occur during the high temperature processing of these alloys or during welding if the imposed strain exhausts the available ductility within this temperature range. Several alloy systems including Ni-base alloys, Ni.Cu alloys, Cu alloys, stainless steels and steels, have been reported to be susceptible to DDC. A complete understanding of the DDC mechanism does not exist, which makes DDC control in actual production conditions a very difficult task. In this study, the DDC resistance was evaluated with different FMs which have different chemical composition. The microstructural features of FMs such as precipitation behavior and grain boundaries morphology were observed, and it were correlated with the DDC susceptibility. The hot ductility test and strainto- fracture test was used to evaluate the DDC susceptibility at high temperature

Impact of ductility on hydraulic fracturing in shales

Science.gov (United States)

MacMinn, Chris; Auton, Lucy

2016-04-01

Hydraulic fracturing is a method for extracting natural gas and oil from low-permeability rocks such as shale via the high-pressure injection of fluid into the bulk of the rock. The goal is to initiate and propagate fractures that will provide hydraulic access deeper into the reservoir, enabling gas or oil to be collected from a larger region of the rock. Fracture is the tensile failure of a brittle material upon reaching a threshold tensile stress, but some shales have a high clay content and may yield plastically before fracturing. Plastic deformation is the shear failure of a ductile material, during which stress relaxes through irreversible rearrangements of the particles of the material. Here, we investigate the impact of the ductility of shales on hydraulic fracturing. We first consider a simple, axisymmetric model for radially outward fluid injection from a wellbore into a ductile porous rock. We use this model to show that plastic deformation greatly reduces the maximum tensile stress, and that this maximum stress does not always occur at the wellbore. We then complement these results with laboratory experiments in an analogue system, and with numerical simulations based on the discrete element method (DEM), both of which suggest that ductile failure can indeed dramatically change the resulting deformation pattern. These results imply that hydraulic fracturing may fail in ductile rocks, or that the required injection rate for fracking may be much larger than the rate predicted from models that assume purely elastic mechanical behavior.

Creep strength and rupture ductility of creep strength enhanced ferritic steels

Energy Technology Data Exchange (ETDEWEB)

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

2010-07-01

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

Ductility loss of ion-irradiated zircaloy-2 in iodine

International Nuclear Information System (INIS)

Shimada, M.; Terasawa, M.; Yamamoto, S.; Kamei, H.; Koizumi, K.

1981-01-01

An ion bombardment simulation technique for neutron irradiation was applied to 'thick' materials to study the effect of radiation damage on the ductility change in Zircaloy-2 in an iodine environment. Specimens were prepared from actual cladding tubes and, prior to the irradiation, they were heat-treated in vacuo at 450, 580, and 700/degree/C for 2 h. Irradiation was performed by 52-MeV alpha particles up to the 0.32 displacements per atom (dpa) at 340/degree/C. Ductility loss begins to appear after 0.03 dpa irradiation, both in iodine and argon gas environments. The iodine presence resulted in ductility reduction, compared with the argon result in all irradiation dose ranges examined. The stress applied during irradiation caused ductility loss to commence at lower dosage than in the case of stress-free irradiation. These results are discussed in relation to the existing stress corrosion cracking models

Prediction of fracture toughness based on experiments with sub-size specimens in the brittle and ductile regimes

Energy Technology Data Exchange (ETDEWEB)

Mahler, Michael, E-mail: Michael.Mahler@kit.edu; Aktaa, Jarir

2016-04-15

For determination of fracture toughness in the brittle regime or ductile fracture in the upper shelf region, special standard specifications are in use e.g. ASTM E399 or ASTM E1820. Due to the rigorous size requirements for specimen testing, it is necessary to use big specimens. To circumvent this problem an approach based on finite element (FE) simulations using the cohesive zone model (CZM) is used. The parameters of the cohesive zone model have been determined using sub-size specimens. With the identified parameters, simulations of standard-size specimens have been performed to successfully predict fracture toughness of standard-size specimens in the brittle and ductile regimes. The objective is to establish small size testing technology for the determination of fracture toughness. - Highlights: • Prediction of fracture toughness on standard-size specimens. • Valid fracture toughness based on sub-size specimens. • Triaxiality dependent cohesive zone model. • Approach works independent on fracture appearance (brittle, ductile).

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.

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.

Bend testing for miniature disks

International Nuclear Information System (INIS)

Huang, F.H.; Hamilton, M.L.; Wire, G.L.

1982-01-01

A bend test was developed to obtain ductility measurements on a large number of alloy variants being irradiated in the form of miniature disks. Experimental results were shown to be in agreement with a theoretical analysis of the bend configuration. Disk specimens fabricated from the unstrained grip ends of previously tested tensile specimens were used for calibration purposes; bend ductilities and tensile ductilities were in good agreement. The criterion for estimating ductility was judged acceptable for screening purposes

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

International Nuclear Information System (INIS)

Kim, Min Gun; Lim, Bok Kyu; Hwang, Jung Gak; Kim, Dong Youl

2005-01-01

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 α+γ is prepared to investigate the static strength and fatigue properties in comparison with fully austempered ductile iron (is treated from γ). 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

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)

Cyclic behavior, development, and characteristics of a ductile hybrid fiber-reinforced polymer (DHFRP) for reinforced concrete members

Science.gov (United States)

Hampton, Francis Patrick

Reinforced concrete (R/C) structures especially pavements and bridge decks that constitute vital elements of the infrastructure of all industrialized societies are deteriorating prematurely. Structural repair and upgrading of these structural elements have become a more economical option for constructed facilities especially in the United States and Canada. One method of retrofitting concrete structures is the use of advanced materials. Fiber reinforced polymer (FRP) composite materials typically are in the form of fabric sheets or reinforcing bars. While the strength and stiffness of the FRP is high, composites are inherently brittle, with limited or no ductility. Conventional FRP systems cannot currently meet ductility demand, and therefore, may fail in a catastrophic failure mode. The primary goal of this research was to develop an optimized prototype 10-mm diameter DHFRP bar. The behavior of the bar under full load reversals to failure was investigated. However, this bar first needed to be designed and manufactured in the Fibrous Materials Research at Drexel University. Material properties were determined through testing to categorize the strength properties of the DHFRP. Similitude was used to demonstrate the scaling of properties from the original model bars. The four most important properties of the DHFRP bars are sufficient strength and stiffness, significant ductility for plasticity to develop in the R/C section, and sufficient bond strength for the R/C section to develop its full strength. Once these properties were determined the behavior of reinforced concrete members was investigated. This included the testing of prototype-size beams under monotonic loading and model and prototype beam-columns under reverse cyclic loading. These tests confirmed the large ductility exhibited by the DHFRP. Also the energy absorption capacity of the bar was demonstrated by the hysteretic behavior of the beam-columns. Displacement ductility factors in the range of 3

Thermoelastic martensite and shape memory effect in ductile Cu-Al-Mn alloys

Science.gov (United States)

Kainuma, R.; Takahashi, S.; Ishida, K.

1996-08-01

Ductile shape memory (SM) alloys of the Cu-AI-Mn system have been developed by controlling the degree of order in the β phase. Additions of Mn to the binary Cu-Al alloy stabilize the β phase and widen the single-phase region to lower temperature and lower Al contents. It is shown that Cu-Al-Mn alloys with low Al contents have either the disordered A2 structure or the ordered L21 structure with a lower degree of order and that they exhibit excellent ductility. The disordered A2 phase martensitically transforms to the disordered Al phase with a high density of twins. The martensite phase formed from the ordered L21 phase has the 18R structure. The SM effect accompanies both the A2 → Al and L21 → 18R martensitic transformations. These alloys exhibit 15 pct strain to failure, 60 to 90 pct rolling reduction without cracking, and 80 to 90 pct recovery from bend test in the martensitic condition. Experimental results on the microstructure, crystal structure, mechanical properties, and shape memory behavior in the ductile Cu-AI-Mn alloys are presented and discussed.

Development of acceptance criteria and damage tolerance analyzes of the ductile iron insert; Framtagning av acceptanskriterier samt skadetaalighetsanalyser av segjaernsinsatsen

Energy Technology Data Exchange (ETDEWEB)

Dillstroem, Peter; Alverlind, Lars; Andersson, Magnus (Inspecta Technology AB (Sweden))

2010-01-15

SKB intends to qualify a test system for detection and sizing of defects deemed to be relevant to the ductile iron insert. In support of this qualification, a damage tolerance analysis indicating the current qualification targets, given assumed damage and failure modes. This report describes the damage tolerance analyzes of different types of defects that are considered relevant of the ductile iron insert. The results are reported separately for each test area (zone) and type of insert (BWRs and PWRs)

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.

Ductile electroactive biodegradable hyperbranched polylactide copolymers enhancing myoblast differentiation.

Science.gov (United States)

Xie, Meihua; Wang, Ling; Guo, Baolin; Wang, Zhong; Chen, Y Eugene; Ma, Peter X

2015-12-01

Myotube formation is crucial to restoring muscular functions, and biomaterials that enhance the myoblast differentiation into myotubes are highly desirable for muscular repair. Here, we report the synthesis of electroactive, ductile, and degradable copolymers and their application in enhancing the differentiation of myoblasts to myotubes. A hyperbranched ductile polylactide (HPLA) was synthesized and then copolymerized with aniline tetramer (AT) to produce a series of electroactive, ductile and degradable copolymers (HPLAAT). The HPLA and HPLAAT showed excellent ductility with strain to failure from 158.9% to 42.7% and modulus from 265.2 to 758.2 MPa. The high electroactivity of the HPLAAT was confirmed by UV spectrometer and cyclic voltammogram measurements. These HPLAAT polymers also showed improved thermal stability and controlled biodegradation rate compared to HPLA. Importantly, when applying these polymers for myotube formation, the HPLAAT significantly improved the proliferation of C2C12 myoblasts in vitro compared to HPLA. Furthermore, these polymers greatly promoted myogenic differentiation of C2C12 cells as measured by quantitative analysis of myotube number, length, diameter, maturation index, and gene expression of MyoD and TNNT. Together, our study shows that these electroactive, ductile and degradable HPLAAT copolymers represent significantly improved biomaterials for muscle tissue engineering compared to HPLA. Copyright © 2015 Elsevier Ltd. All rights reserved.

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...

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

Simultaneous improvement of strength, ductility and corrosion resistance of Al2024 alloy processed by cryoforging followed by ageing

International Nuclear Information System (INIS)

Kumar Singh, Amit; Ghosh, Sumit; Mula, Suhrit

2016-01-01

The aim of the present study is to simultaneous improvement of strength and ductility as well as corrosion resistance of ultrafine grained 2024 Al-alloy processed by multiaxial cryoforging (MAF) and cryorolling followed by ageing. The evolution of ultrafine grained microstructure during MAF followed by ageing is investigated using optical and transmission electron microscopy. Both multiaxially forged (MAFed) and cryorolled (CRed) samples showed an improvement in yield strength (YS) with a corresponding decrease in the ductility. Aging treatment not only improved the YS, but also its ductility. Improvement in the ductility after ageing is confirmed by the fractography analysis. Corrosion resistance of the MAFed+aged samples found to be higher compared to that of the MAFed and coarse grained counterpart. The corrosion behavior has been analyzed in the light of open circuit potential (OCP), solutionizing, grain size and precipitation strengthening mechanisms. SEM images of the corroded samples also corroborated the corrosion test results.

Brittle and ductile rupture of 16MND5 steel. Irradiation effect

International Nuclear Information System (INIS)

Al Mundheri, M.; Soulat, P.; Pineau, A.

1986-06-01

Toughness tests have been made on 16MND5 steel (A508Cl3 steel) - before and after irradiation at 290 0 C (3.10 19 n/cm 2 , E > 1 MeV). It is shown that toughness is lowered following the irradiation and that it is a decreasing function of the thickness of the test pieces. In parallel, tests on three geometries of entailed specimens, prepared in the non-irradiated material, have been made at different temperatures to apply the methodology of local approach of ductile-brittle rupture [fr

Ductile-brittle transition behaviour of PLA/o-MMT films during the physical aging process

Directory of Open Access Journals (Sweden)

M. Ll. Maspoch

2015-03-01

Full Text Available The ductile-brittle transition behaviour of organo modified montmorillonite-based Poly(lactic acid films (PLA/o-MMT was analysed using the Essential Work of Fracture (EWF methodology, Small Punch Tests (SPT and Enthalpy relaxation analysis. While the EWF methodology could only be applied successfully to de-aged samples, small punch test (SPT was revealed as more effective for a mechanical characterization during the transient behaviour from ductile to brittle. According to differential scanning calorimetry (DSC results, physical aging at 30°C of PLA/o-MMT samples exhibited slower enthalpy relaxation kinetics as compared to the pristine polymer. Although all samples exhibited an equivalent thermodynamic state after being stored one week at 30°C, significant differences were observed in the mechanical performances. These changes could be attributed to the toughening mechanisms promoted by o-MMT.

Effect of Temperature Reversion on Hot Ductility and Flow Stress-Strain Curves of C-Mn Continuously Cast Steels

Science.gov (United States)

Dong, Zhihua; Li, Wei; Long, Mujun; Gui, Lintao; Chen, Dengfu; Huang, Yunwei; Vitos, Levente

2015-08-01

The influence of temperature reversion in secondary cooling and its reversion rate on hot ductility and flow stress-strain curve of C-Mn steel has been investigated. Tensile specimens were cooled at various regimes. One cooling regime involved cooling at a constant rate of 100 °C min-1 to the test temperature, while the others involved temperature reversion processes at three different reversion rates before deformation. After hot tensile test, the evolution of mechanical properties of steel was analyzed at various scales by means of microstructure observation, ab initio prediction, and thermodynamic calculation. Results indicated that the temperature reversion in secondary cooling led to hot ductility trough occurring at higher temperature with greater depth. With increasing temperature reversion rate, the low temperature end of ductility trough extended toward lower temperature, leading to wider hot ductility trough with slightly reducing depth. Microstructure examinations indicated that the intergranular fracture related to the thin film-like ferrite and (Fe,Mn)S particles did not changed with varying cooling regimes; however, the Widmanstatten ferrite surrounding austenite grains resulted from the temperature reversion process seriously deteriorated the ductility. In addition, after the temperature reversion in secondary cooling, the peak stress on the flow curve slightly declined and the peak of strain to peak stress occurred at higher temperature. With increasing temperature reversion rate, the strain to peak stress slightly increased, while the peak stress showed little variation. The evolution of plastic modulus and strain to peak stress of austenite with varying temperature was in line with the theoretical prediction on Fe.

Multiscale modeling of ductile failure in metallic alloys

Science.gov (United States)

Pardoen, Thomas; Scheyvaerts, Florence; Simar, Aude; Tekoğlu, Cihan; Onck, Patrick R.

2010-04-01

Micromechanical models for ductile failure have been developed in the 1970s and 1980s essentially to address cracking in structural applications and complement the fracture mechanics approach. Later, this approach has become attractive for physical metallurgists interested by the prediction of failure during forming operations and as a guide for the design of more ductile and/or high-toughness microstructures. Nowadays, a realistic treatment of damage evolution in complex metallic microstructures is becoming feasible when sufficiently sophisticated constitutive laws are used within the context of a multilevel modelling strategy. The current understanding and the state of the art models for the nucleation, growth and coalescence of voids are reviewed with a focus on the underlying physics. Considerations are made about the introduction of the different length scales associated with the microstructure and damage process. Two applications of the methodology are then described to illustrate the potential of the current models. The first application concerns the competition between intergranular and transgranular ductile fracture in aluminum alloys involving soft precipitate free zones along the grain boundaries. The second application concerns the modeling of ductile failure in friction stir welded joints, a problem which also involves soft and hard zones, albeit at a larger scale.

Effect of the crack-starter weld condition on the nil-ductility transition temperature

International Nuclear Information System (INIS)

Satoh, Masanobu; Funada, Tatsuo; Tomimatsu, Minoru

1985-01-01

In ASME Code Sec. III, the value of the reference nil-ductility temperature RT sub(EDT) has an important significance to determine the result of the fracture mechanics evaluation. While in the standard both the drop-weight test and Charpy impact test are required to determine the RT sub(NDT), in practice it is normally determined only by the nil-ductility transition temperature (T sub(EDT)) obtained by the drop-weight test. The cases of data scatter in T sub(NDT) were investigated to establish appropriate conditions of crack-starter bead welding. Drop-weight tests were carried out for nuclear vessel steels by changing welding conditions to examine the effects of welding amperage and shapes of welding table on T sub(NDT). The results show that the preparation of crack-starter bead by small welding amperage should not be allowed, because it makes the measured T sub(NDT) non-conservative, and that it is important to use a welding table which increases the cooling rate of specimen. Furthermore, the authors proposed methods for estimating T sub(NDT) of nuclear vessel steels by using Charpy transition temperatures. (author)

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.

Turbulent breakage of ductile aggregates.

Science.gov (United States)

Marchioli, Cristian; Soldati, Alfredo

2015-05-01

In this paper we study breakage rate statistics of small colloidal aggregates in nonhomogeneous anisotropic turbulence. We use pseudospectral direct numerical simulation of turbulent channel flow and Lagrangian tracking to follow the motion of the aggregates, modeled as sub-Kolmogorov massless particles. We focus specifically on the effects produced by ductile rupture: This rupture is initially activated when fluctuating hydrodynamic stresses exceed a critical value, σ>σ(cr), and is brought to completion when the energy absorbed by the aggregate meets the critical breakage value. We show that ductile rupture breakage rates are significantly reduced with respect to the case of instantaneous brittle rupture (i.e., breakage occurs as soon as σ>σ(cr)). These discrepancies are due to the different energy values at play as well as to the statistical features of energy distribution in the anisotropic turbulence case examined.

Unstable propagation behavior of a ductile crack in SUS-304 stainless steel under high compliance tensile loading

International Nuclear Information System (INIS)

Tomoda, Yoshio

1981-01-01

In relation to the safe maintenance of nuclear power plants, it is necessary to prevent reactor coolant pipings from burst type failure caused by the unstable propagation of defects and cracks, such as stress corrosion cracking and fatigue cracks. In ductile materials, crack propagation is stable in tensile loading under fixed grip condition, when a specimen is controlled to deform in proportion to the increase of tensile load. However, it has been known that the instability of ductile cracks occurs after tensile load reached the maximum, especially under constant loading condition arising in the loading devices with high compliance or low tensile rigidity. In order to confirm the reliability of SUS 304 stainless pipes subjected to SCC, the crack propagation behavior was examined with the specimens having center cracks, using both testing machines with high compliance and low compliance. The instability of ductile cracks and the propagation velocity of unstable cracks were analyzed, and the calculated results were compated with the experimental results. Not only the compliance of testing machines but also the conditions of specimens affected the propagation of cracks. (Kako, I.)

From brittle to ductile: a structure dependent ductility of diamond nanothread.

Science.gov (United States)

Zhan, Haifei; Zhang, Gang; Tan, Vincent B C; Cheng, Yuan; Bell, John M; Zhang, Yong-Wei; Gu, Yuantong

2016-06-07

As a potential building block for the next generation of devices/multifunctional materials that are spreading in almost every technology sector, one-dimensional (1D) carbon nanomaterial has received intensive research interests. Recently, a new ultra-thin diamond nanothread (DNT) has joined this palette, which is a 1D structure with poly-benzene sections connected by Stone-Wales (SW) transformation defects. Using large-scale molecular dynamics simulations, we found that this sp(3) bonded DNT can transition from brittle to ductile behaviour by varying the length of the poly-benzene sections, suggesting that DNT possesses entirely different mechanical responses than other 1D carbon allotropes. Analogously, the SW defects behave like a grain boundary that interrupts the consistency of the poly-benzene sections. For a DNT with a fixed length, the yield strength fluctuates in the vicinity of a certain value and is independent of the "grain size". On the other hand, both yield strength and yield strain show a clear dependence on the total length of DNT, which is due to the fact that the failure of the DNT is dominated by the SW defects. Its highly tunable ductility together with its ultra-light density and high Young's modulus makes diamond nanothread ideal for the creation of extremely strong three-dimensional nano-architectures.

A new insight into ductile fracture of ultrafine-grained Al-Mg alloys.

Science.gov (United States)

Yu, Hailiang; Tieu, A Kiet; Lu, Cheng; Liu, Xiong; Liu, Mao; Godbole, Ajit; Kong, Charlie; Qin, Qinghua

2015-04-08

It is well known that when coarse-grained metals undergo severe plastic deformation to be transformed into nano-grained metals, their ductility is reduced. However, there are no ductile fracture criteria developed based on grain refinement. In this paper, we propose a new relationship between ductile fracture and grain refinement during deformation, considering factors besides void nucleation and growth. Ultrafine-grained Al-Mg alloy sheets were fabricated using different rolling techniques at room and cryogenic temperatures. It is proposed for the first time that features of the microstructure near the fracture surface can be used to explain the ductile fracture post necking directly. We found that as grains are refined to a nano size which approaches the theoretical minimum achievable value, the material becomes brittle at the shear band zone. This may explain the tendency for ductile fracture in metals under plastic deformation.

Origin of the extra low creep ductility of copper without phosphorus

Energy Technology Data Exchange (ETDEWEB)

Sandstroem, Rolf [Corrosion and Metals Research Inst., Materials Science and Engineering, Royal Inst. of Technology, Stockholm (Sweden); Rui Wu [Corrosion and Metals Research Inst., Stockholm (Sweden)

2007-02-15

Around 1990 it was discovered that pure copper could have extra low creep ductility in the temperature interval 180 to 250 deg C. If 50 ppm phosphorus was added to the material the low creep ductility disappeared. A creep cavitation model is presented that can quantitatively describe the observed creep ductility for copper with and without phosphorus. A new model called the double ledge model has been introduced that explains why the nucleation rate of creep cavities is often proportional to the creep rate. The phosphorus agglomerates at the grain boundaries, locks their sliding and thereby reduces the formation and growth of cavities. This is the main reason why extra low creep ductility does not occur in phosphorus alloyed copper.

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.

Miniaturization of specimens for mechanical testing

International Nuclear Information System (INIS)

Harling, O.K.; Kohse, G.

1987-01-01

The development of mechanical property tests based on bending of a 3 mm diameter by (typically) 0.25 mm thick disk is described. Slow strain rate testing of such a disk is used to obtain tensile properties. Finite element computer modelling is used to extract yield stress values with accuracies of at least +- 10% of uniaxial tensile test values for a variety of materials. Analytical estimates of ductility from disk bend test values are possible for low-ductility materials. Work directed toward finite element calculations for ductility and ultimate tensile strength is also discussed. Preliminary data indicating the feasibility of high strain rate testing for estimation of ductile-to-brittle transition temperatures, and an example of the successful application of miniature bend testing in obtaining relative fatigue information are also presented. (author)

Effect of mechanical properties on erosion resistance of ductile materials

Science.gov (United States)

Levin, Boris Feliksovih

Solid particle erosion (SPE) resistance of ductile Fe, Ni, and Co-based alloys as well as commercially pure Ni and Cu was studied. A model for SPE behavior of ductile materials is presented. The model incorporates the mechanical properties of the materials at the deformation conditions associated with SPE process, as well as the evolution of these properties during the erosion induced deformation. An erosion parameter was formulated based on consideration of the energy loss during erosion, and incorporates the material's hardness and toughness at high strain rates. The erosion model predicts that materials combining high hardness and toughness can exhibit good erosion resistance. To measure mechanical properties of materials, high strain rate compression tests using Hopkinson bar technique were conducted at strain rates similar to those during erosion. From these tests, failure strength and strain during erosion were estimated and used to calculate toughness of the materials. The proposed erosion parameter shows good correlation with experimentally measured erosion rates for all tested materials. To analyze subsurface deformation during erosion, microhardness and nanoindentation tests were performed on the cross-sections of the eroded materials and the size of the plastically deformed zone and the increase in materials hardness due to erosion were determined. A nanoindentation method was developed to estimate the restitution coefficient within plastically deformed regions of the eroded samples which provides a measure of the rebounding ability of a material during particle impact. An increase in hardness near the eroded surface led to an increase in restitution coefficient. Also, the stress rates imposed below the eroded surface were comparable to those measured during high strain-rate compression tests (10sp3-10sp4 ssp{-1}). A new parameter, "area under the microhardness curve" was developed that represents the ability of a material to absorb impact energy. By

Study of austempering reaction in austempered ductile iron

International Nuclear Information System (INIS)

Ja'far Farhan Al-Sharab; Sharma, D.G.R.; Samsul Bahar Sadli

1996-01-01

Austempered Ductile Iron (ADI) is an important engineering material which is gaining popularity. The conventional belief that austempered ductile iron, when heat treated satisfactorily, contains bainite, is now disproved by recent experiments. Our present work on the study of the reaction products of heat treated ADI by x-ray diffraction confirms the recent view. The results of x-ray diffraction studies on the structural constituents od ADI for various durations of austempering are presented and discussed

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...... degree than we have seen previously. It is the aim of the present paper to present ductile iron as a modern engineering material and present the many different possibilities that the material hides. Focus will be on the latest research in solidification and melt treatment. But for completeness...

Ductile fracture theories for pressurised pipes and containers

Science.gov (United States)

Erdogan, F.

1976-01-01

Two mechanisms of fracture are distinguished. Plane strain fractures occur in materials which do not undergo large-scale plastic deformations prior to and during a possible fracture deformation. Plane stress or high energy fractures are generally accompanied by large inelastic deformations. Theories for analyzing plane stress are based on the concepts of critical crack opening stretch, K(R) characterization, J-integral, and plastic instability. This last is considered in some detail. The ductile fracture process involves fracture initiation followed by a stable crack growth and the onset of unstable fracture propagation. The ductile fracture propagation process may be characterized by either a multiparameter (discrete) model, or some type of a resistance curve which may be considered as a continuous model expressed graphically. These models are studied and an alternative model is also proposed for ductile fractures which cannot be modeled as progressive crack growth phenomena.

Forced tearing of ductile and brittle thin sheets.

Science.gov (United States)

Tallinen, T; Mahadevan, L

2011-12-09

Tearing a thin sheet by forcing a rigid object through it leads to complex crack morphologies; a single oscillatory crack arises when a tool is driven laterally through a brittle sheet, while two diverging cracks and a series of concertinalike folds forms when a tool is forced laterally through a ductile sheet. On the other hand, forcing an object perpendicularly through the sheet leads to radial petallike tears in both ductile and brittle materials. To understand these different regimes we use a combination of experiments, simulations, and simple theories. In particular, we describe the transition from brittle oscillatory tearing via a single crack to ductile concertina tearing with two tears by deriving laws that describe the crack paths and wavelength of the concertina folds and provide a simple phase diagram for the morphologies in terms of the material properties of the sheet and the relative size of the tool.

Prediction of hot-ductility of steels during continuous casting using artificial neural networks

International Nuclear Information System (INIS)

Liu, W.J.; Emadi, D.; Essadiqi, E.

2000-01-01

During continuous casting, transversal cracks can be developed due to tensile stress in temperature regions where the steel exhibits a low ductility. The cracking tendency during continuous casting depends on the steel chemistry and the casting parameters such as lubrication, mold type, secondary cooling and bending/unbending temperatures. To prevent cracking one needs to predict the hot-ductility of a material under continuous-casting conditions. However, hot-ductility is one of the poorly understood material behaviors and cannot be readily modeled using conventional techniques. In the present study, we used an alternative method, namely Artificial Neural Networks (ANN), to model the ductility of a steel under continuous casting conditions. A hot-ductility database was established based on published literature. Several standard three-layer ANN models were then trained using data randomly selected from the database. The outputs of the ANN models were subsequently compared with the remaining data in the database. The results indicate that ANN is a suitable modelling technique for hot-ductility prediction. (author)

Effects of Alloying Elements (Mo, Ni, and Cu on the Austemperability of GGG-60 Ductile Cast Iron

Directory of Open Access Journals (Sweden)

Erkan Konca

2017-08-01

Full Text Available The interest in austempered ductile irons (ADI is continuously increasing due to their various advantageous properties over conventional ductile irons and some steels. This study aimed to determine the roles of alloying elements Ni, Cu, and Mo, on the austemperability of GGG-60 ductile cast iron. Two different sets of GGG-60 (EN-GJS-600-3 samples, one set alloyed with Ni and Cu and the other set alloyed with Mo, Ni, and Cu, were subjected to austempering treatments at 290 °C, 320 °C, and 350 °C. A custom design heat treatment setup, consisting of two units with the top unit (furnace serving for austenitizing and the 200 L capacity bottom unit (stirred NaNO2-KNO3 salt bath serving for isothermal treatment, was used for the experiments. It was found that austempering treatment at 290 °C increased the hardness of the Ni-Cu alloyed GGG-60 sample by about 44% without causing a loss in its ductility. In the case of the Mo-Ni-Cu alloyed sample, the increase in hardness due to austempering reached to almost 80% at the same temperature while some ductility was lost. Here, the microstructural investigation and mechanical testing results of the austempered samples are presented and the role of alloying elements (Mo, Ni, and Cu on the austemperability of GGG-60 is discussed.

Robustness Analysis of a Wide-Span Timber Structure with Ductile Behaviour

DEFF Research Database (Denmark)

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

2010-01-01

This paper considers robustness evaluation of a wide span timber truss structure where the ductile behavior is taken into account. The robustness analysis is based on a structural reliability framework used on a simplified mechanical system modelling a timber truss system. A measure of ductile...... behaviour is introduced and for different values of this measure the robustness indices are estimated. The results indicate that the robustness of a timber truss system can be increased by taking the ductile behavior into....

Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride

Science.gov (United States)

2015-08-01

ARL-RP-0528 ● AUG 2015 US Army Research Laboratory Sample Size Induced Brittle-to- Ductile Transition of Single-Crystal Aluminum...originator. ARL-RP-0528 ● AUG 2015 US Army Research Laboratory Sample Size Induced Brittle-to- Ductile Transition of Single-Crystal...Sample Size Induced Brittle-to- Ductile Transition of Single-Crystal Aluminum Nitride 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

Ductility and resistance to deformation of EhP975 alloy during hot plastic working

International Nuclear Information System (INIS)

Baturin, A.I.; Martynov, A.I.

1982-01-01

Results of investigations into ductility and resistance to deformation of the EhP975 most heat-resistant difficult-to-form alloy of commercial melting in 1000-1200 deg C temperature range and at deformation rates epsilon = 0.1 - 25 s - 1 are presented. It is shown that ductility of EhP975 alloy grows rather slowly with increase of temperature approximately up to 1075 deg C, then sharp growth of ductility up to the maximum at 1120-1125 deg C is observed; ductility decreases above this temperature zone. It was also established that ductility of EhP975 alloy grows with increase of preliminary deformation degree. It is marked that high temperature annealing increases ductility of EhP975 alloy in comparison with (cast state), especially noticeably at high deformation rates

Effect of alloying elements on the shape memory properties of ductile Cu-Al-Mn alloys

International Nuclear Information System (INIS)

Sutou, Y.; Kainuma, R.; Ishida, K.

1999-01-01

The effect of alloying elements on the M s temperature, ductility and the shape memory properties of Cu-Al-Mn ductile shape memory (SM) alloys was investigated by differential scanning calorimetry, cold-rolling and tensile test techniques. It was found that the addition of Au, Si and Zn to the Cu 73 -Al 17 -Mn 10 alloy stabilized the martensite (6M) phase increasing the M s temperature, while the addition of Ag, Co, Cr, Fe, Ni, Sn and Ti decreased the stability of the martensite phase, decreasing the M s temperature. The SM properties were improved by the addition of Co, Ni, Cr and Ti. (orig.)

Prediction of creep-fatigue life by use of creep rupture ductility

International Nuclear Information System (INIS)

Yamaguchi, Koji; Suzuki, Naoyuki; Ijima, Kiyoshi; Kanazawa, Kenji

1985-01-01

It was clarified that tension strain hold reduced creep-fatigue life of many engineering materials in different degrees depending on material, temperature and test duration. However the reduction in the life due to holding for various durations could be correlated to the fraction of intergranular facets on fracture surfaces which was considered to be an index of the damage introduced during strain hold. This fraction of intergranular facets by creep-fatigue failure exhibited a direct relation to the creep rupture ductility of the material tested at the same temperature and for the same creep-fatigue life-time. From these results an empirical equation has been derived as follow; (Δ sub(epsilonsub(i)))/Dsub(c).(N sub(h sup(α))) = C, where Δ sub(epsilonsub(i)) is inelastic strain range, Dsub(c) is the creep rupture ductility for the same duration as creep-fatigue life time, Nsub(h) is the creep-fatigue life under tension strain hold conditions, and α and C are constants depending on the material and testing temperature. From the equation the life prediction is possible for a given inelastic strain range Δ sub(epsilonsub(i)) if the constants α and C, and Dsub(c) are known. The value of α was found to be 0.62 and 0.74 for various austenitic stainless steels and NCF800 at 600 0 C and 700 0 C, respectively, and 0.69 for 1 1/4Cr-1/2Mo steel at 600 0 C. The value of C was found to be 0.50 and 0.59 for various austenitic stainless steels and NCF800 at 600 0 C and 700 0 C, respectively, and 0.49 for 1 1/4Cr-1/2Mo steel at 600 0 C. The creep rupture ductility Dsub(c) is available in the NRIM Creep Data Sheets up to 10 5 h for multi-heats of many kinds of heat resistant alloys. (author)

Fracture of longitudinally cracked ductile tubes

International Nuclear Information System (INIS)

Larsson, H.; Bernard, J.

1978-01-01

Various bulging factor and plasticity correction factor formulations are discussed and a new plasticity correction factor leading to a simple failure law is proposed. Failure stresses predicted by the usual Linear Elastic Fracture Mechanics formula corrected for plasticity are shown to be identical with the Dowling and Townley two-criteria approach if the relevant parameters are chosen in a suitable manner. Burst tests on AISI 304 stainless steel tubes performed at the Joint Research Centre, Ispra are described. The strengthening effect of the sealing patch was taken into account by replacing the Folias bulging factor by a smaller empirical factor determined by Bernard and Henry from fatigue crack growth tests. A flow stress sigma and a toughness Ksub(c) were derived which apply to the prediction of the onset of stable crack growth in 304 stainless steel tubes at room temperature. For other ductile materials and temperatures tentative formulae are proposed. (author)

The quantification of specimen size effects in the ductile-brittle transition for C-Mn steel

International Nuclear Information System (INIS)

Knee, N.; Worthington, P.J.; Moskovic, R.

1989-02-01

It is now generally accepted that the temperature range of the brittle to ductile transition, determined using fracture mechanics specimens, is dependent of the specimen size for ferritic steels. This size effect arises through increasing constraint at the crack tip as the specimen thickness increases together with an increasing volume of material sampled. The size effect can be quantified in terms of a shift in temperature for a given toughness level. This was determined in the present work from fracture toughness/temperature curves obtained by performing fracture toughness tests on eight 100 mm thick compact tension specimens and 40 25 mm thick compact tension specimens over the ductile-brittle transition range of a C-Mn steel. The emphasis is on the development of a practical methodology to quantify the size effect from a limited but still appreciable number of tests. (author)

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.)

Highly ductile UV-shielding polymer composites with boron nitride nanospheres as fillers.

Science.gov (United States)

Fu, Yuqiao; Huang, Yan; Meng, Wenjun; Wang, Zifeng; Bando, Yoshio; Golberg, Dmitri; Tang, Chengchun; Zhi, Chunyi

2015-03-20

Polymer composites with enhanced mechanical, thermal or optical performance usually suffer from poor ductility induced by confined mobility of polymer chains. Herein, highly ductile UV-shielding polymer composites are successfully fabricated. Boron nitride (BN) materials, with a wide band gap of around ∼6.0 eV, are used as fillers to achieve the remarkably improved UV-shielding performance of a polymer matrix. In addition, it is found that spherical morphology BN as a filler can keep the excellent ductility of the composites. For a comparison, it is demonstrated that traditional fillers, including conventional BN powders can achieve the similar UV-shielding performance but dramatically decrease the composite ductility. The mechanism behind this phenomenon is believed to be lubricant effects of BN nanospheres for sliding of polymer chains, which is in consistent with the thermal analyses. This study provides a new design to fabricate UV-shielding composite films with well-preserved ductility.

Brittle to ductile transition in densified silica glass.

Science.gov (United States)

Yuan, Fenglin; Huang, Liping

2014-05-22

Current understanding of the brittleness of glass is limited by our poor understanding and control over the microscopic structure. In this study, we used a pressure quenching route to tune the structure of silica glass in a controllable manner, and observed a systematic increase in ductility in samples quenched under increasingly higher pressure. The brittle to ductile transition in densified silica glass can be attributed to the critical role of 5-fold Si coordination defects (bonded to 5 O neighbors) in facilitating shear deformation and in dissipating energy by converting back to the 4-fold coordination state during deformation. As an archetypal glass former and one of the most abundant minerals in the Earth's crest, a fundamental understanding of the microscopic structure underpinning the ductility of silica glass will not only pave the way toward rational design of strong glasses, but also advance our knowledge of the geological processes in the Earth's interior.

A kinematic measurement for ductile and brittle failure of materials using digital image correlation

Directory of Open Access Journals (Sweden)

M.M. Reza Mousavi

2016-12-01

Full Text Available This paper addresses some material level test which is done on quasi-brittle and ductile materials in the laboratory. The displacement control experimental program is composed of mortar cylinders under uniaxial compression shows quasi-brittle behavior and seemingly round-section aluminum specimens under uniaxial tension represents ductile behavior. Digital Image Correlation gives full field measurement of deformation in both aluminum and mortar specimens. Likewise, calculating the relative displacement of two points located on top and bottom of virtual LVDT, which is virtually placed on the surface of the specimen, gives us the classical measure of strain. However, the deformation distribution is not uniform all over the domain of specimens mainly due to imperfect nature of experiments and measurement devices. Displacement jumps in the fracture zone of mortar specimens and strain localization in the necking area for the aluminum specimen, which are reflecting different deformation values and deformation gradients, is compared to the other regions. Since the results are inherently scattered, it is usually non-trivial to smear out the stress of material as a function of a single strain value. To overcome this uncertainty, statistical analysis could bring a meaningful way to closely look at scattered results. A large number of virtual LVDTs are placed on the surface of specimens in order to collect statistical parameters of deformation and strain. Values of mean strain, standard deviation and coeffcient of variations for each material are calculated and correlated with the failure type of the corresponding material (either brittle or ductile. The main limiters for standard deviation and coeffcient of variations for brittle and ductile failure, in pre-peak and post-peak behavior are established and presented in this paper. These limiters help us determine whether failure is brittle or ductile without determining of stress level in the material.

Process for improving the low temperature ductility of tungsten-base composites

International Nuclear Information System (INIS)

Zukas, E.G.

1975-05-01

At temperatures below about 100 0 C, liquid-phase-sintered tungsten-base composites fail in a brittle manner because of the formation of cleavage cracks in the tungsten spheroids. Improving the ductility, then, would require some alloying addition or treatment which would improve the ductility of these spheroids, or some method of changing the stress distribution, such as putting the surface in compression, which would reduce stress concentrations and thereby require a higher load to initiate fracture. The ductilizing process used here consists of coating the composite with a ductile metal followed by heat treating at a high enough temperature to insure sufficient diffusion so that the coat and base become integral. The ductile coat is now the 'piece' surface, and the initiation of cleavage cracks requires much greater stresses. Coats of copper, nickel, gold, and cobalt have been used successfully. A possible added advantage is that the surface properties can now be controlled if certain reflective properties or corrosion resistance are needed. Also soldering or low temperature brazing operations are feasible, allowing the construction or assembly of intricate shapes which could not be accomplished previously. (U.S.)

Energetic approach for ductile tearing

International Nuclear Information System (INIS)

Marie, St.

1999-01-01

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 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 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 i and G 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)

Influence of rare earths on shrinkage porosity in thin walled ductile cast iron

DEFF Research Database (Denmark)

Pedersen, Karl Martin; Tiedje, Niels Skat

2009-01-01

Ductile cast iron has been cast in test bars with thickness from 2 to 10 mm. The rare earth elements La and Ce have been added to some of the castings to evaluate their influence on microstructure and shrinkage tendency. Both La and Ce increased the graphite nodule count, especially for thickness...

A study on the corrosion and erosion behavior of electroless nickel and TiAlN/ZrN duplex coatings on ductile iron

Energy Technology Data Exchange (ETDEWEB)

Lin, Chung-Kwei [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China); Hsu, Cheng-Hsun, E-mail: chhsu@ttu.edu.tw [Department of Materials Engineering, Tatung University, Taipei 104, Taiwan (China); College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Cheng, Yin-Hwa [Department of Materials Engineering, Tatung University, Taipei 104, Taiwan (China); Ou, Keng-Liang [College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Department of Mechanical Engineering, National Central University, Taoyuan 320, Taiwan (China); Lee, Sheng-Long [Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China)

2015-01-01

Highlights: • Electroless nickel was used as an interlayer for TiAlZrN-coated ductile iron. • The duplex coatings evidently improved corrosion resistance of ductile iron. • The duplex coated ductile iron showed a good erosion resistance. - Abstract: This study utilized electroless nickel (EN) and cathodic arc evaporation (CAE) technologies to deposit protective coatings onto ductile iron. Polarization corrosion tests were performed in 3.5 wt.% sodium chloride, and also erosion tests were carried out by using Al{sub 2}O{sub 3} particles (∼177 μm in size and Mohr 7 scale) of about 5 g. Surface morphologies of the corroded and eroded specimens were observed separately. To further understand the coating effects on both the corrosive and erosive behavior of ductile iron, coating structure, morphology, and adhesion were analyzed using X-ray diffractormeter, scanning electron microscopy, and Rockwell-C indenter, respectively. The results showed that the EN exhibited an amorphous structure while the CAE-TiAlN/ZrN coating was a multilayered nanocrystalline. When the TiAlN/ZrN coated specimen with EN interlayer could effectively increase the adhesion strength between the CAE coating and substrate. Consequently, the combination of TiAlN/ZrN and EN delivered a better performance than did the monolithic EN or TiAlN/ZrN for both corrosion and erosion protection.

A study on the corrosion and erosion behavior of electroless nickel and TiAlN/ZrN duplex coatings on ductile iron

International Nuclear Information System (INIS)

Lin, Chung-Kwei; Hsu, Cheng-Hsun; Cheng, Yin-Hwa; Ou, Keng-Liang; Lee, Sheng-Long

2015-01-01

Highlights: • Electroless nickel was used as an interlayer for TiAlZrN-coated ductile iron. • The duplex coatings evidently improved corrosion resistance of ductile iron. • The duplex coated ductile iron showed a good erosion resistance. - Abstract: This study utilized electroless nickel (EN) and cathodic arc evaporation (CAE) technologies to deposit protective coatings onto ductile iron. Polarization corrosion tests were performed in 3.5 wt.% sodium chloride, and also erosion tests were carried out by using Al 2 O 3 particles (∼177 μm in size and Mohr 7 scale) of about 5 g. Surface morphologies of the corroded and eroded specimens were observed separately. To further understand the coating effects on both the corrosive and erosive behavior of ductile iron, coating structure, morphology, and adhesion were analyzed using X-ray diffractormeter, scanning electron microscopy, and Rockwell-C indenter, respectively. The results showed that the EN exhibited an amorphous structure while the CAE-TiAlN/ZrN coating was a multilayered nanocrystalline. When the TiAlN/ZrN coated specimen with EN interlayer could effectively increase the adhesion strength between the CAE coating and substrate. Consequently, the combination of TiAlN/ZrN and EN delivered a better performance than did the monolithic EN or TiAlN/ZrN for both corrosion and erosion protection

Review of current research and application of ductile cast iron quality monitoring technologies in Chinese foundry industry

Directory of Open Access Journals (Sweden)

Da-yong Li

2015-07-01

Full Text Available There is a long history of studying and making use of ductile cast iron in China. Over the years, the foundrymen in China have carried out a lot of valuable research and development work for measuring parameters and controlling the quality in ductile cast iron production. Many methods, such as rapid metallographic phase, thermal analysis, eutectic expansion ratio, surface tension measurement, melt electrical resistivity, oxygen and sulfur activity measurement, ultrasonic measurement and sound frequency measurement, have been used and have played important roles in Chinese casting production in the past. These methods can be generally classified as liquid testing and solid testing according to the sample state. Based on the analysis of the present situation of these methods applied in the Chinese metal casting industry, the authors consider that there are two difficult technical problems to be currently solved in monitoring ductile iron quality. One is to seek an effective method for quickly evaluating the nodularizing result through on-the-spot sample analysis before the liquid iron is poured into the mould. The other is to find a nondestructive method for accurately identifying casting quality before castings are delivered.

Multi-scale modeling of ductile failure in metallic alloys

International Nuclear Information System (INIS)

Pardoen, Th.; Scheyvaerts, F.; Simar, A.; Tekoglu, C.; Onck, P.R.

2010-01-01

Micro-mechanical models for ductile failure have been developed in the seventies and eighties essentially to address cracking in structural applications and complement the fracture mechanics approach. Later, this approach has become attractive for physical metallurgists interested by the prediction of failure during forming operations and as a guide for the design of more ductile and/or high-toughness microstructures. Nowadays, a realistic treatment of damage evolution in complex metallic microstructures is becoming feasible when sufficiently sophisticated constitutive laws are used within the context of a multilevel modelling strategy. The current understanding and the state of the art models for the nucleation, growth and coalescence of voids are reviewed with a focus on the underlying physics. Considerations are made about the introduction of the different length scales associated with the microstructure and damage process. Two applications of the methodology are then described to illustrate the potential of the current models. The first application concerns the competition between intergranular and transgranular ductile fracture in aluminum alloys involving soft precipitate free zones along the grain boundaries. The second application concerns the modeling of ductile failure in friction stir welded joints, a problem which also involves soft and hard zones, albeit at a larger scale. (authors)

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.

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

Thermal effects on the enhanced ductility in non-monotonic uniaxial tension of DP780 steel sheet

Science.gov (United States)

Majidi, Omid; Barlat, Frederic; Korkolis, Yannis P.; Fu, Jiawei; Lee, Myoung-Gyu

2016-11-01

To understand the material behavior during non-monotonic loading, uniaxial tension tests were conducted in three modes, namely, the monotonic loading, loading with periodic relaxation and periodic loading-unloadingreloading, at different strain rates (0.001/s to 0.01/s). In this study, the temperature gradient developing during each test and its contribution to increasing the apparent ductility of DP780 steel sheets were considered. In order to assess the influence of temperature, isothermal uniaxial tension tests were also performed at three temperatures (298 K, 313 K and 328 K (25 °C, 40 °C and 55 °C)). A digital image correlation system coupled with an infrared thermography was used in the experiments. The results show that the non-monotonic loading modes increased the apparent ductility of the specimens. It was observed that compared with the monotonic loading, the temperature gradient became more uniform when a non-monotonic loading was applied.

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...

The effects of boro-tempering heat treatment on microstructural properties of ductile iron

International Nuclear Information System (INIS)

Kayali, Yusuf; Yalcin, Yilmaz

2011-01-01

In this study, the effects of boro-tempering heat treatment on microstructural properties of ductile iron were investigated. Test samples with dimensions of 10 x 10 x 55 mm were boronized at 900 o C for 1, 3 and 5 h and then tempered at four different temperatures (250, 300, 350 and 450 o C) for 1 h. Both optical microscopy and scanning electron microscopy were used to reveal the microstructural details of coating and matrix of boro-tempered ductile iron. X-ray diffraction was used to determine the constituents of the coating layer. The boride layer formed on the surface of boro-tempered ductile cast iron is tooth shape form and consisted of FeB and Fe 2 B phases. The thickness of boride layer increases as the boronizing time increases and tempering temperature decreases. Tempering temperature is more effective than boronizing time on the matrix structure. Boro-tempering heat treatment reduces the formation of lower and upper ausferritic matrix temperature according to classical austempering. This causes formation of upper ausferritic matrix in the sample when tempered at 300 o C. This is in contrast to general case which is the formation of lower ausferritic matrix via austempering at this temperature.

Influence of the static strain ageing on the ductile-to-brittle transition in C-Mn steel

International Nuclear Information System (INIS)

Marais, A.

2012-01-01

Ferritic steels for industrial structures have a brittle-ductile transition toughness and impact energy with temperature. Their resistance to the brittle fracture plays an essential role in the safety certification of industrial structures. Nowadays, the performance and the durability are key issues for major players such as EDF. In these approaches ductile-to-brittle transition toughness and impact energy, toughness is predicted from resilience. Several previous studies have shown that the probability of cleavage fracture can be adequately described in brittle plateau by a local approach to fracture. However, these studies assume that the material does not undergo strain aging, which is rarely relevant for low carbon steels and low calmed down. The work consisted firstly to characterize the behavior and secondly to propose a robust and explicit modeling of the observed phenomena. Characterization consisted of performing tensile tests between -150 C and 20 C for several strain rates. A model able to simulate the static aging is identified by implementing an appropriate and systematic strategy. Impact resistance test allows us to build the curve of ductile-to-brittle transition of the material for different conditions to understand and observe the influence of static strain aging on the failure. Finally, the modeling of the brittle fracture has been described for all experimental conditions tested using the model developed and identified in the previous section to predict the transition for different material conditions. (author)

Scratch deformation behavior of thermoplastic materials with significant differences in ductility

International Nuclear Information System (INIS)

Hadal, R.S.; Misra, R.D.K.

2005-01-01

A comparative study of the scratch deformation behavior of neat ethylene-propylene copolymers and polypropylene with significant differences in ductility is made by combining morphological examination by electron microscopy and scratch deformation parameters by atomic force microscopy. Also, the deformation behavior during scratch tests is examined for their respective long and short chain polymers. The ability of polymeric materials to resist scratch deformation under identical scratch test conditions follows the sequence (from maximum resistance to minimum resistance): short chain polypropylene > long chain polypropylene > short chain ethylene-propylene > long chain ethylene-propylene. The scratch tracks in ethylene-propylene copolymers were characterized by a consecutive parabolic pattern containing voids, while polypropylenes exhibited zig-zag periodic scratch tracks. The greater plastic flow in ethylene-propylene copolymers is encouraged by the high ductility of the copolymer and the ability to nucleate microvoids. The quasi-static periodic scratch tracks are a consequence of sequential accumulation and release of tangential force and represents the stick-slip process. The susceptibility to scratch deformation is discussed in terms of modulus, elastic recovery, scratch hardness, and entanglement density of polymeric materials. A higher effective entanglement density and percentage crystallinity of short chain polymers is helpful in enhancing scratch resistance as compared to their respective long chain polymers

Dislocation dynamics modelling of the ductile-brittle-transition

International Nuclear Information System (INIS)

Hennecke, Thomas; Haehner, Peter

2009-01-01

Many materials like silicon, tungsten or ferritic steels show a transition between high temperature ductile fracture with stable crack grow and high deformation energy absorption and low temperature brittle fracture in an unstable and low deformation mode, the ductile-brittle-transition. Especially in steels, the temperature transition is accompanied by a strong increase of the measured fracture toughness over a certain temperature range and strong scatter in the toughness data in this transition regime. The change in fracture modes is affected by dynamic interactions between dislocations and the inhomogeneous stress fields of notches and small cracks. In the present work a dislocation dynamics model for the ductile-brittle-transition is proposed, which takes those interactions into account. The model can explain an increase with temperature of apparent toughness in the quasi-brittle regime and different levels of scatter in the different temperature regimes. Furthermore it can predict changing failure sites in materials with heterogeneous microstructure. Based on the model, the effects of crack tip blunting, stress state, external strain rate and irradiation-induced changes in the plastic flow properties can be discussed.

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 iron mains. 192.369 Section 192.369 Transportation Other Regulations Relating to Transportation... ductile iron mains. (a) Each service line connected to a cast iron or ductile iron main must be connected...

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

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)

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

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)

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

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

Chemically vapor-deposited tungsten: its high temperature strength and ductility

International Nuclear Information System (INIS)

Bryant, W.A.

1977-01-01

The high temperature tensile ductility (as measured by total elongation normal to the growth direction) of chemically vapor-deposited tungsten was found to be significantly greater than previously reported. A correlation was found between ductility and void content. However, voids were found to have essentially no effect on the high temperature strength of this material, which is considerably weaker than powder metallurgy tungsten. (Auth.)

Mechanical properties of ductile cast iron and cast steel for intermediate level waste transport containers

International Nuclear Information System (INIS)

Gray, I.L.S.; Sievwright, R.W.T.; Egid, B.; Ajayi, F.; Donelan, P.

1994-01-01

UK Nirex Ltd is developing Type B re-usable shielded transport containers (RSTCs) in a range of shielding thicknesses to transport intermediate level radioactive waste (ILW) to a deep repository. The designs are of an essentially monolithic construction and rely principally on the plastic flow of their material to absorb the energies involved in impact events. Nirex has investigated the feasibility of manufacturing the RSTCs from ductile cast iron (DCI) or cast steel instead of from forgings, since this would bring advantages of reduced manufacturing time and costs. However, cast materials are perceived to lack toughness and ductility and it is necessary to show that sufficient fracture toughness can be obtained to preclude brittle failure modes, particularly at low temperatures. The mechanical testing carried out as part of that programme is described. It shows how the measured properties have been used to demonstrate avoidance of brittle fracture and provide input to computer modelling of the drop tests. (author)

Heterogeneous multi-layered IF steel with simultaneous high strength and good ductility

Science.gov (United States)

Zhang, Ling; Jiang, Xiaojuan; Wang, Yuhui; Chen, Qiang; Chen, Zhen; Zhang, Yonghong; Huang, Tianlin; Wu, Guilin

2017-07-01

Multi-layered IF steel samples were designed and fabricated by hot compression followed by cold forging of an alternating stack of cold-rolled and annealed IF steel sheets, with an aim to improve the strength of the material without losing much ductility. A very good combination of strength and ductility was achieved by proper annealing after deformation. Microstructural analysis by electron back-scatter diffraction revealed that the good combination of strength and ductility is related to a characteristic hierarchical structure that is characterized by layered and lamella structures with different length scales.

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.

Effect of boron on the hot ductility of 2.25Cr1Mo steel

International Nuclear Information System (INIS)

Song, S.-H.; Guo, A.-M.; Shen, D.-D.; Yuan, Z.-X.; Liu, J.; Xu, T.-D.

2003-01-01

The effect of boron on the hot ductility of 2.25Cr1Mo steel is investigated by means of a Gleeble 2000 thermomechanical simulator. There is a trough in the hot ductility-temperature curve, which is located between 1000 and 700 deg. C. The ductility trough shifts to lower temperatures with increasing boron content and the hot brittle range becomes shallow and narrow. In general, boron may improve the steel hot ductility in that it may retard the formation of pro-eutectoid ferrite and increase grain boundary cohesion. These effects may be related to the segregation of boron to austenite grain boundaries

Influence of intercritical austempering on the microstructure and mechanical properties of austempered ductile cast iron (ADI)

International Nuclear Information System (INIS)

Panneerselvam, Saranya; Putatunda, Susil K.; Gundlach, Richard; Boileau, James

2017-01-01

The focus of this investigation was to examine the influence of intercritical austempering process on the microstructure and mechanical properties of low-alloyed austempered ductile cast iron (ADI). The investigation also examined the influence of intercritical austempering process on the plane strain fracture toughness of the material. The effect of both austenitization and austempering temperature on the microstructure and mechanical properties was examined. The microstructural analysis was carried out using optical microscopy, scanning electron microscopy and X-ray diffraction. The test results indicate that by intercritical austempering it is possible to produce proeutectoid ferrite in the matrix microstructure. Lower austenitizing temperature produces more proeutectoid ferrite in the matrix. Furthermore, the yield, tensile strength and the fracture toughness of the ADI decreases with decrease in austenitizing temperature. A considerable increase in ductility was observed in the samples with higher proeutectoid ferrite content. The fracture surfaces of the ADI samples revealed that dimple ductile fracture produced higher fracture toughness of 60±5 MPa√m in this intercritically austempered ADI.

Influence of intercritical austempering on the microstructure and mechanical properties of austempered ductile cast iron (ADI)

Energy Technology Data Exchange (ETDEWEB)

Panneerselvam, Saranya [Wayne State University, Detroit, MI (United States); Putatunda, Susil K., E-mail: sputa@eng.wayne.edu [Wayne State University, Detroit, MI (United States); Gundlach, Richard [Element Materials Technology, MI (United States); Boileau, James [Ford Motor Company, Dearborn, MI (United States)

2017-05-10

The focus of this investigation was to examine the influence of intercritical austempering process on the microstructure and mechanical properties of low-alloyed austempered ductile cast iron (ADI). The investigation also examined the influence of intercritical austempering process on the plane strain fracture toughness of the material. The effect of both austenitization and austempering temperature on the microstructure and mechanical properties was examined. The microstructural analysis was carried out using optical microscopy, scanning electron microscopy and X-ray diffraction. The test results indicate that by intercritical austempering it is possible to produce proeutectoid ferrite in the matrix microstructure. Lower austenitizing temperature produces more proeutectoid ferrite in the matrix. Furthermore, the yield, tensile strength and the fracture toughness of the ADI decreases with decrease in austenitizing temperature. A considerable increase in ductility was observed in the samples with higher proeutectoid ferrite content. The fracture surfaces of the ADI samples revealed that dimple ductile fracture produced higher fracture toughness of 60±5 MPa√m in this intercritically austempered ADI.

A ductile fracture analysis using a local damage model

Energy Technology Data Exchange (ETDEWEB)

Benseddiq, N. [Laboratoire de Mecanique et de Rheologie de Tours, Ecole Nationale d' Ingenieurs du Val de Loire (ENIVL), Rue de la Chocolaterie, 41000 Blois Cedex (France)], E-mail: nbensedd@polytech-lille.fr; Imad, A. [Laboratoire de Mecanique de Lille (UMR CNRS 8107), USTL, Ecole Polytechnique Universitaire de Lille Cite Scientifique, Avenue P. Langevin, 59655 Villeneuve d' Ascq Cedex (France)

2008-04-15

In this study, the Gurson-Tvergaard-Needleman (GTN) model is used to investigate ductile tearing. The sensitivity of the model parameters has been examined from literature data. Three types of parameters have been reported: the 'constitutive parameters'q{sub 1}, q{sub 2} and q{sub 3}, the 'initial material and nucleation parameters' and the 'critical and final failure parameters'. Each parameter in this model has been analysed in terms of various results in the literature. Both experimental and numerical results have been obtained for notched round and CT specimens to characterize ductile failure in a NiCr steel (12NC6) with a small initial void volume fraction f{sub 0} (f{sub 0}=0.001%). Ductile crack growth, defined by the J-{delta}a curve, has been correctly simulated using the numerical calculations by adjusting the different parameters of the GTN model in the calibration procedure.

A brittle-fracture methodology for three-dimensional visualization of ductile deformation micromechanisms

NARCIS (Netherlands)

Tasan, C.C.; Hoefnagels, J.P.M.; Geers, M.G.D.

2009-01-01

An improved experimental methodology is developed and successfully evaluated to visualize deformation-induced microevents in ductile sheet metal. This easy-to-use methodology consists in a well-controlled brittle separation of samples previously deformed in a ductile manner, whereby a

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.

Influence of TiC precipitation in austenitic stainless steel on strength, ductility and helium embrittlement

International Nuclear Information System (INIS)

Kesternich, W.; Matta, M.K.; Rothaut, J.

1984-01-01

Creep experiments were performed on 1.4970 (German DIN standard) and 316 (AISI standard) type austenitic steels after various thermomechanical pretreatments and after α-implantation. The microstructure introduced by the pretreatments was characterized by transmission electron microscopy and the behaviour of strength and ductility is correlated to the dislocation and precipitate distributions. He embrittlement can be suppressed in these simulation experiments when dispersive TiC precipitate distributions are produced by the proper pretreatments or are allowed to form during creep testing. It is shown that adequate pretreatment results in a significantly superior behaviour of the 1.4970 steel as compared to the 316 type steel in all three investigated properties, i.e. strength, ductility and resistance to He embrittlement. (orig.)

New Mechanism on Synergistic Effect of Nitrite and Triethanolamine Addition on the Corrosion of Ductile Cast Iron

Directory of Open Access Journals (Sweden)

K. T. Kim

2016-01-01

Full Text Available In general, we compared the different inhibition mechanisms of organic inhibitor with that of anodic inhibitor. When triethanolamine or nitrite was added separately to tap water for inhibiting the corrosion of ductile cast iron, large amounts of inhibitor were needed. This is because the corrosion inhibitors had to overcome the galvanic corrosion that occurs between graphite and matrix. In this work, we investigated the corrosion of ductile cast iron in tap water with/without inhibitors. The corrosion rate was measured using chemical immersion test and electrochemical methods, including anodic polarization test. The inhibited surface was analyzed using EPMA and XPS. Test solutions were analyzed by performing FT-IR measurement. When triethanolamine and nitrite coexisted in tap water, synergistic effect built up, and the inhibition effect was ca. 30 times more effective than witnessed with single addition. This work focused on the synergistic effect brought about by nitrite and triethanolamine and its novel mechanism was also proposed.

Mechanistic origin and prediction of enhanced ductility in magnesium alloys

Science.gov (United States)

Wu, Zhaoxuan; Ahmad, Rasool; Yin, Binglun; Sandlöbes, Stefanie; Curtin, W. A.

2018-01-01

Development of ductile magnesium alloys is key to their use in reducing the weight of vehicles and other applications. Wu et al. tackle this issue by determining the underlying mechanisms in unprocessed magnesium alloys. Dilute amounts of solutes enhanced certain ductility-improving mechanisms over ones that cause brittle fracture. From this, the authors developed a theory that may be helpful for screening the large number of potential magnesium alloy compositions.

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.

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.

Plastic strain induced damage evolution and martensitic transformation in ductile materials at cryogenic temperatures

International Nuclear Information System (INIS)

Garion, C.; Skoczen, B.T.

2002-01-01

The Fe-Cr-Ni stainless steels are well known for their ductile behavior at cryogenic temperatures. This implies development and evolution of plastic strain fields in the stainless steel components subjected to thermo-mechanical loads at low temperatures. The evolution of plastic strain fields is usually associated with two phenomena: ductile damage and strain induced martensitic transformation. Ductile damage is described by the kinetic law of damage evolution. Here, the assumption of isotropic distribution of damage (microcracks and microvoids) in the Representative Volume Element (RVE) is made. Formation of the plastic strain induced martensite (irreversible process) leads to the presence of quasi-rigid inclusions of martensite in the austenitic matrix. The amount of martensite platelets in the RVE depends on the intensity of the plastic strain fields and on the temperature. The evolution of the volume fraction of martensite is governed by a kinetic law based on the accumulated plastic strain. Both of these irreversible phenomena, associated with the dissipation of plastic power, are included into the constitutive model of stainless steels at cryogenic temperatures. The model is tested on the thin-walled corrugated shells (known as bellows expansion joints) used in the interconnections of the Large Hadron Collider, the new proton storage ring being constructed at present at CERN

Revealing the extra-high ductility and toughness of micro+duplex medium+Mn steel in a large temperature range from 200 ℃ to -196 ℃

DEFF Research Database (Denmark)

Cao, Wenquan; Hu, Jun; Dong, Han

2014-01-01

A medium-Mn steel (0.2C5Mn) was processed by intercritical annealing at different temperature (625℃ and 650℃) after forging and hot rolling. The microstructures were characterized by transmission electron microscopy and the mechanical properties were measured by tensile tests and impact tests...... at different temperatures. It was found that an ultrafine grained micro-duplex structure existed with austenite and ferrite laths formed by means of an austenite reverse transformation during intercritical annealing (shortly called ART-annealing). Ultrahigh ductility (total elongation larger than 30%) could...... be obtained in the temperature range from 200℃ to -196℃. And significantly delayed transition from ductile to brittle and no less than 200J impact toughness at -40℃ could be obtained in the ART-annealed medium-Mn steel. Based on the analysis of microstructure and mechanical properties, the enhanced ductility...

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.

An approach to ductile fracture resistance modelling in pipeline steels

Energy Technology Data Exchange (ETDEWEB)

Pussegoda, L.N.; Fredj, A. [BMT Fleet Technology Ltd., Kanata (Canada)

2009-07-01

Ductile fracture resistance studies of high grade steels in the pipeline industry often included analyses of the crack tip opening angle (CTOA) parameter using 3-point bend steel specimens. The CTOA is a function of specimen ligament size in high grade materials. Other resistance measurements may include steady state fracture propagation energy, critical fracture strain, and the adoption of damage mechanisms. Modelling approaches for crack propagation were discussed in this abstract. Tension tests were used to calibrate damage model parameters. Results from the tests were then applied to the crack propagation in a 3-point bend specimen using modern 1980 vintage steels. Limitations and approaches to overcome the difficulties associated with crack propagation modelling were discussed.

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.)

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.

Ultimate strength and ductility of steel reinforced concrete beam-columns

International Nuclear Information System (INIS)

Shohara, Ryoichi

1991-01-01

The ultimate strength and ductility of SRC beam-columns are investigated using the data gathered in Architectural Institute of Japan. Though the simple superposed strength formula in AIJ standard underestimates the strength of SRC beam-column failed in flexure, the generalized superposed strength formula estimates it satisfactory. The strength formula in AIJ standard does not good agreement with test data. The SRC beam-column failed in shear has almost equalductility with that failed in flexure owing to the encased steel. Author presents the formulas which estimate the ultimate deformation angle for SRC beam-columns. (author)

Ductile cast irons: microstructure influence on fatigue crack propagation resistance

Directory of Open Access Journals (Sweden)

Mauro Cavallini

2010-07-01

Full Text Available Microstructure influence on fatigue crack propagation resistance in five different ductile cast irons (DCI was investigated. Four ferrite/pearlite volume fractions were considered, performing fatigue crack propagation tests according to ASTM E647 standard (R equals to 0.1, 0.5 and 0.75, respectively. Results were compared with an austempered DCI. Damaging micromechanisms were investigated according to the following procedures: - “traditional” Scanning Electron Microscope (SEM fracture surfaces analysis; - SEM fracture surface analysis with 3D quantitative analysis; - SEM longitudinal crack profile analysis - Light Optical Microscope (LOM transversal crack profile analysis;

Microstructure and wear behaviors of WC–12%Co coating deposited on ductile iron by electric contact surface strengthening

International Nuclear Information System (INIS)

Qi, Xiaoben; Zhu, Shigen; Ding, Hao; Zhu, Zhengkun; Han, Zhibing

2013-01-01

WC–12%Co powders deposited on ductile iron by electric contact strengthening were studied. This technology was based on the application of the contact resistance heating between the electrode and work piece to form a wear resistant layer on ductile iron. The microstructure, microhardness distribution, phase transformation and wear behaviors of the coating were investigated using optical microscope, scanning electron microscope, Vickers hardness (HV 0.5 ), X-ray diffraction, rolling contact wear tests. The results showed that the WC–12%Co coating by electric contact strengthening was metallurgically bonded to the ductile iron. Additionally, the effect of experimental parameters on microhardness and wear resistance of coatings were studied using orthogonal experiment. The results showed that compared with (A) electric current and (B) rotating speed, (C) contact force displays the most significant effect on microhardness and wear resistance of coatings. The coatings produced at A = 19 kA, B = 0.3 r/min and C = 700 N possessed highest microhardness of 1073 HV 0.5 and wear resistance.

Influence of creep ductility on creep-fatigue behaviour of 20%Cr/25%Ni/Nb stainless steel

International Nuclear Information System (INIS)

Gladwin, D.; Miller, D.A.

1985-01-01

The influence of creep ductility on creep-fatigue endurance of 20%Cr/25%Ni/Nb stainless steel has been examined. In order to induce different creep ductilities in the 20/25/Nb stainless steel, three different thermo-mechanical routes were employed. These resulted in a range of ductilities (3-36%) being obtained at the strain rates of interest. Strain controlled slow-fast creep-fatigue cycles were used with strain rates of 10 -6 s -1 , 10 -7 s -1 in tension and 10 -3 s -1 in compression. It was found that creep ductility strongly influenced the creep-fatigue endurance of the 20/25/Nb stainless steel. When failure was creep dominated endurance was found to be directly proportional to the creep ductility. A ductility exhaustion model has been used to successfully predict creep-fatigue endurance when failure was creep dominated. (author)

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......Experimental observations have shown that the roughness of fracture surfaces exhibit certain characteristic scaling properties. Here, calculations are carried out to explore the extent to which a ductile damage/fracture constitutive relation can be used to model fracture surface roughness scaling...... 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...

Evaluation of ductile-brittle transition behavior with neutron irradiation in nuclear reactor pressure vessel steels using small punch test

International Nuclear Information System (INIS)

Kim, M. C.; Lee, B. S.; Oh, Y. J.

2003-01-01

A Small Punch (SP) test was performed to evaluate the ductile-brittle transition temperature before and after neutron irradiation in Reactor Pressure Vessel (RPV) steels produced by different manufacturing (refining) processes. The results were compared to the standard transition temperature shifts from the Charpy test and Master Curve fracture toughness test in accordance with the ASTM standard E1921. The samples were taken from 1/4t location of the vessel thickness and machined into a 10x10x0.5mm dimension. Irradiation of the samples was carried out in the research reactor at KAERI (HANARO) at about 290 .deg. C of the different fluence levels respectively. SP tests were performed in the temperature range of RT to -196 .deg. C using a 2.4mm diameter ball. For the materials before and after irradiation, SP transition temperatures (T sp ), which are determined at the middle of the upper and lower SP energies, showed a linear correlation with the Charpy index temperature, T 41J . T sp from the irradiated samples was increased as the fluence level increased and was well within the deviation range of the unirradiated data. The TSP had a correlation with the reference temperature (T 0 ) from the master curve method using a pre-cracked Charpy V-notched (PCVN) specimen

The causes of geometry effects in ductile tearing

International Nuclear Information System (INIS)

Dexter, R.J.; Griesbach, T.J.

1993-01-01

An adequate understanding of geometry effects in ductile tearing can only be achieved when the different causes of the effects are distinguished and these geometry effects are linked to particular micromechanical fracture processes or global deformation mechanisms. It is shown that the micromechanical process of ductile (fibrous) fracture is dependent on achieving a critical strain, which is only slightly dependent on the stress state for the range of triaxiality conditions in pressure vessels and through-cracked plates. Under certain conditions, the crack tip strain can be shown to scale with the value of the J integral and there is a direct connection between J and the underlying micro mechanical process. This connection is lost for significant crack extension or large-scale plasticity. Nevertheless the J integral may still be use on an empirical basis under some conditions. Under fully-plastic conditions the primary source of geometry dependence in the J-R curves is due to the geometry dependence of the shape and volume of the plastic region that develops around the uncracked ligament. This occurs because J is essentially proportional to the total plastic work done on the specimen. If it can be assured that the fracture mode in both the test specimen and the structure will remain fully fibrous, it is conservative to extrapolate J-R curves generated from small compact specimens for the analysis of pressure vessel crack stability. 132 refs., 12 figs., 3 tabs

Behaviour of porous ductile solids at low stress triaxiality in different modes of deformation

DEFF Research Database (Denmark)

Tvergaard, Viggo

2015-01-01

The effect of low stress triaxiality on ductile failure is investigated for a material subject to pure shear or to stress states in the vicinity of pure shear. Many recent studies of ductile failure under low hydrostatic tension have focused on shear with superposed tension, which can result...... that the behaviour of a porous ductile material at low stress triaxiality depends a great deal on the mode of deformation....

Effects of composition and heat treatments on the strength and ductility of Fe-Cr-Co alloys

International Nuclear Information System (INIS)

Kubarych, K.G.

1980-06-01

The relationship between the microstructure and mechanical properties of spinodally decomposed Fe-Cr-Co ductile permanent magnet alloys was investigated using transmission electron microscopy, electron diffraction, tensile testing, and Charpy impact testing. Isothermal aging and step aging of four alloys (Fe-28 wt % Cr-15 wt % Co, Fe-23 wt % Cr-15-wt % Co-5 wt % V, Fe-23 wt % Cr-15 wt % Co-3 wt % V-2 wt % Ti, and Fe-31 wt % Cr-23 % Co) resulted in decomposition into two phases, an Fe-Co rich (α 1 ) phase and a Cr rich (α 2 ) phase. The microstructural features of the decomposition products were consistent with those expected from a spinodal reaction and agree with the reported work on the Fe-Cr-Co system. An Fe-23 wt % Cr-15 wt % Co-5 wt % V alloy was found to have, among the four alloys, the best combinations of strength and ductility

Modelling of ductile and cleavage fracture by local approach

International Nuclear Information System (INIS)

Samal, M.K.; Dutta, B.K.; Kushwaha, H.S.

2000-08-01

This report describes the modelling of ductile and cleavage fracture processes by local approach. It is now well known that the conventional fracture mechanics method based on single parameter criteria is not adequate to model the fracture processes. It is because of the existence of effect of size and geometry of flaw, loading type and rate on the fracture resistance behaviour of any structure. Hence, it is questionable to use same fracture resistance curves as determined from standard tests in the analysis of real life components because of existence of all the above effects. So, there is need to have a method in which the parameters used for the analysis will be true material properties, i.e. independent of geometry and size. One of the solutions to the above problem is the use of local approaches. These approaches have been extensively studied and applied to different materials (including SA33 Gr.6) in this report. Each method has been studied and reported in a separate section. This report has been divided into five sections. Section-I gives a brief review of the fundamentals of fracture process. Section-II deals with modelling of ductile fracture by locally uncoupled type of models. In this section, the critical cavity growth parameters of the different models have been determined for the primary heat transport (PHT) piping material of Indian pressurised heavy water reactor (PHWR). A comparative study has been done among different models. The dependency of the critical parameters on stress triaxiality factor has also been studied. It is observed that Rice and Tracey's model is the most suitable one. But, its parameters are not fully independent of triaxiality factor. For this purpose, a modification to Rice and Tracery's model is suggested in Section-III. Section-IV deals with modelling of ductile fracture process by locally coupled type of models. Section-V deals with the modelling of cleavage fracture process by Beremins model, which is based on Weibulls

Seismic Performance of RC Beam-Column Connections with Continuous Rectangular Spiral Transverse Reinforcements for Low Ductility Classes

Directory of Open Access Journals (Sweden)

Mohammadamin Azimi

2014-01-01

Full Text Available The seismic performance of RC columns could be significantly improved by continuous spiral reinforcement as a result of its adequate ductility and energy dissipation capacity. Due to post-earthquake brittle failure observations in beam-column connections, the seismic behaviour of such connections could greatly be improved by simultaneous application of this method in both beams and columns. In this study, a new proposed detail for beam to column connection introduced as “twisted opposing rectangular spiral” was experimentally and numerically investigated and its seismic performance was compared against normal rectangular spiral and conventional shear reinforcement systems. In this study, three full scale beam to column connections were first designed in conformance with Eurocode (EC2-04 for low ductility class connections and then tested by quasistatic cyclic loading recommended by ACI Building Code (ACI 318-02. Next, the experimental results were validated by numerical methods. Finally, the results revealed that the new proposed connection could improve the ultimate lateral resistance, ductility, and energy dissipation capacity.

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.

Effects of neutron irradiation and fatigue on ductility of stainless steel DIN 1.4948

International Nuclear Information System (INIS)

Vries, M.I. de; Schaaf, B. van der; Staal, H.U.; Elen, J.D.

1978-10-01

Test specimens of stainless steel DIN 1.4948, which is similar to AISI type 304, have been irradiated at 723 K and 823 K up to fluences of 1.10 23 neutrons (n).m -2 and 5.10 24 n.m -2 (E > 0.1 MeV). These are representative conditions for the SNR-300 reactor vessel and inner components after 16 years of operation. High temperature (723 K to 1023 K) tensile tests at strain rates (depsilon/dt) from 10 -7 s -1 to 10 s -1 show a considerable decrease of tensile ductility. The extent depends on helium content, test temperature and strain rate. The atomic helium fractions of 3.10 -7 and 7.10 -6 result from the reactions of thermal neutrons with the 14 ppm boron, present in the steel. Helium embrittlement sets in at strain rates below 1 s -1 to 10 s -1 (the range of interest for Bethe-Tait accident analyses). A minimum total elongation value of 6% is shown at 923 K. The post-irradiation fatigue life is reduced by up to about 50% due to intergranular cracking. The combination of irradiation and fatigue causes a decrease of ductility after a smaller number of prior fatigue cycles than in the case of unirradiated material. (Auth.)

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

Directory of Open Access Journals (Sweden)

Myszka D.

2015-04-01

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

Unexpected pressure induced ductileness tuning in sulfur doped polycrystalline nickel metal

Directory of Open Access Journals (Sweden)

Cheng Guo

2018-02-01

Full Text Available The sulfur induced embrittlement of polycrystalline nickel (Ni metal has been a long-standing mystery. It is suggested that sulfur impurity makes ductile Ni metal brittle in many industry applications due to various mechanisms, such as impurity segregation and disorder-induced melting etc. Here we report an observation that the most ductile measurement occurs at a critical sulfur doping concentration, 14 at.% at pressure from 14 GPa up to 29 GPa through texture evolution analysis. The synchrotron-based high pressure texturing measurements using radial diamond anvil cell (rDAC X-ray diffraction (XRD techniques reveal that the activities of slip systems in the polycrystalline nickel metal are affected by sulfur impurities and external pressures, giving rise to the changes in the plastic deformation of the nickel metal. Dislocation dynamics (DD simulation on dislocation density and velocity further confirms the pressure induced ductilization changes in S doped Ni metal. This observation and simulation suggests that the ductilization of the doped polycrystalline nickel metal can be optimized by engineering the sulfur concentration under pressure, shedding a light on tuning the mechanical properties of this material for better high pressure applications.

Unexpected pressure induced ductileness tuning in sulfur doped polycrystalline nickel metal

Science.gov (United States)

Guo, Cheng; Yang, Yan; Tan, Liuxi; Lei, Jialin; Guo, Shengmin; Chen, Bin; Yan, Jinyuan; Yang, Shizhong

2018-02-01

The sulfur induced embrittlement of polycrystalline nickel (Ni) metal has been a long-standing mystery. It is suggested that sulfur impurity makes ductile Ni metal brittle in many industry applications due to various mechanisms, such as impurity segregation and disorder-induced melting etc. Here we report an observation that the most ductile measurement occurs at a critical sulfur doping concentration, 14 at.% at pressure from 14 GPa up to 29 GPa through texture evolution analysis. The synchrotron-based high pressure texturing measurements using radial diamond anvil cell (rDAC) X-ray diffraction (XRD) techniques reveal that the activities of slip systems in the polycrystalline nickel metal are affected by sulfur impurities and external pressures, giving rise to the changes in the plastic deformation of the nickel metal. Dislocation dynamics (DD) simulation on dislocation density and velocity further confirms the pressure induced ductilization changes in S doped Ni metal. This observation and simulation suggests that the ductilization of the doped polycrystalline nickel metal can be optimized by engineering the sulfur concentration under pressure, shedding a light on tuning the mechanical properties of this material for better high pressure applications.

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.

Ductility behavior of irradiated path B alloys

International Nuclear Information System (INIS)

Yang, W.J.S.; Hamilton, M.L.

1983-01-01

The objective of this study was to assess the practicality of using five Path B alloys in their current form as structural materials in the Fusion First-Wall/Blanket by evaluating both their postirradiation ductility and the corresponding microstructures

Ductile thermoset polymers via controlling network flexibility.

Science.gov (United States)

Hameed, N; Salim, N V; Walsh, T R; Wiggins, J S; Ajayan, P M; Fox, B L

2015-06-18

We report the design and synthesis of a polymer structure from a cross-linkable epoxy-ionic liquid system which behaves like a hard and brittle epoxy thermoset, perfectly ductile thermoplastic and an elastomer, all depending on controllable network compositions.

Influence of radiation-induced segregation on ductility of a nickel-silicon alloy

International Nuclear Information System (INIS)

Packan, N.H.; Schroeder, H.; Kesternich, W.

1986-01-01

Flat tensile specimens 60 μm thick of Ni-8 at. % Si were irradiated to bulk damage levels of 0.1 to 0.3 dpa with either 7 MeV protons or 28 MeV alpha particles at 750 K. The alpha bombarded specimens incurred 750 at. ppM He per 0.1 dpa in the course of their damage-generating irradiation. Radiation-induced silicon segregation gave rise to Ni 3 Si layers at internal and external surfaces. Postirradiation tensile tests conducted either at 300 K or 720 K revealed fully ductile (chisel-edged) transgranular fracture profiles. There were no significant differences between the proton-bombarded specimens and the unbombarded controls, both exhibiting >25% total elongations, while the alpha-bombarded specimens showed ductile fractures with somewhat lower (17 to 18%) elongation values probably due to hardening caused by small helium bubbles. Certain specimens that were preimplanted with 250 to 1000 at. ppM He at 970 K to encourage intergranular failure and expose grain boundaries did fail intergranularly. It is concluded that radiation-induced silicon segregation does not cause intrinsic embrittlement

Influence of Casting Section Thickness on Fatigue Strength of Austempered Ductile Iron

Science.gov (United States)

Olawale, J. O.; Ibitoye, S. A.

2017-10-01

The influence of casting section thickness on fatigue strength of austempered ductile iron was investigated in this study. ASTM A536 65-45-12 grade of ductile iron was produced, machined into round samples of 10, 15, 20 and 25 mm diameter, austenitized at a temperature of 820 °C, quenched into an austempering temperature (TA) of 300 and 375 °C and allowed to be isothermally transformed at these temperatures for a fixed period of 2 h. From the samples, fatigue test specimens were machined to conform to ASTM E-466. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) methods were used to characterize microstructural morphology and phase distribution of heat-treated samples. The fatigue strength decreases as the section thickness increases. The SEM image and XRD patterns show a matrix of acicular ferrite and carbon-stabilized austenite with ferrite coarsening and volume fraction of austenite reducing as the section thickness increases. The study concluded that the higher the value of carbon-stabilized austenite the higher the fatigue strength while it decreases as the ausferrite structure becomes coarse.

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......-deformation response and crack development of representative sections of the reinforced composites, and iv) detailing, designing and testing of large scale prefabricated link slab elements. In addition, an application of ductile Engineered Cementitious Composite (ECC) in prefabricated floor panels is presented...... crack widths and crack spacing measurements are obtained, which can characterize the tensile behavior of ECC. In chapter 3 on interfacial bond, the bond slip behavior and crack development, between the reinforcement and surrounding cementitious matrix is investigated in a unique test setup with special...

Comparing the Structure and Mechanical Properties of Welds on Ductile Cast Iron (700 MPa under Different Heat Treatment Conditions

Directory of Open Access Journals (Sweden)

Ronny M. Gouveia

2018-01-01

Full Text Available The weldability of ductile iron, as widely known, is relatively poor, essentially due to its typical carbon equivalent value. The present study was developed surrounding the heat treatability of welded joints made with a high strength ductile cast iron detaining an ultimate tensile strength of 700 MPa, and aims to determine which heat treatment procedures promote the best results, in terms of microstructure and mechanical properties. These types of alloys are suitable for the automotive industry, as they allow engineers to reduce the thickness of parts while maintaining mechanical strength, decreasing the global weight of vehicles and providing a path for more sustainable development. The results allow us to conclude that heat treatment methodology has a large impact on the mechanical properties of welded joints created from the study material. However, the thermal cycles suffered during welding promote the formation of ledeburite areas near the weld joint. This situation could possibly be dealt through the implementation of post-welding heat treatments (PWHT with specific parameters. In contrast to a ductile cast iron tested in a previous work, the bull-eye ductile cast iron with 700 MPa ultimate tensile strength presented better results during the post-welding heat treatment than during preheating.

Fatigue limit prediction of ferritic-pearlitic ductile cast iron considering stress ratio and notch size

Science.gov (United States)

Deguchi, T.; Kim, H. J.; Ikeda, T.

2017-05-01

The mechanical behavior of ductile cast iron is governed by graphite particles and casting defects in the microstructures, which can significantly decrease the fatigue strength. In our previous study, the fatigue limit of ferritic-pearlitic ductile cast iron specimens with small defects ((\\sqrt{{area}}=80˜ 1500{{μ }}{{m}})) could successfully be predicted based on the \\sqrt{{area}} parameter model by using \\sqrt{{area}} as a geometrical parameter of defect as well as the tensile strength as a material parameter. In addition, the fatigue limit for larger defects could be predicted based on the conventional fracture mechanics approach. In this study, rotating bending and tension-compression fatigue tests with ferritic-pearlitic ductile cast iron containing circumferential sharp notches as well as smooth specimens were performed to investigate quantitatively the effects of defect. The notch depths ranged 10 ˜ 2500 μm and the notch root radii were 5 and 50 μm. The stress ratios were R = -1 and 0.1. The microscopic observation of crack propagation near fatigue limit revealed that the fatigue limit was determined by the threshold condition for propagation of a small crack emanating from graphite particles. The fatigue limit could be successfully predicted as a function of R using a method proposed in this study.

Effects of chloride ions on corrosion of ductile iron and carbon steel in soil environments.

Science.gov (United States)

Song, Yarong; Jiang, Guangming; Chen, Ying; Zhao, Peng; Tian, Yimei

2017-07-31

Chloride is reported to play a significant role in corrosion reactions, products and kinetics of ferrous metals. To enhance the understanding of the effects of soil environments, especially the saline soils with high levels of chloride, on the corrosion of ductile iron and carbon steel, a 3-month corrosion test was carried out by exposing ferrous metals to soils of six chloride concentrations. The surface morphology, rust compositions and corrosion kinetics were comprehensively studied by visual observation, scanning electron microscopy (SEM), X-Ray diffraction (XRD), weight loss, pit depth measurement, linear polarization and electrochemical impedance spectroscopy (EIS) measurements. It showed that chloride ions influenced the characteristics and compositions of rust layers by diverting and participating in corrosion reactions. α-FeOOH, γ-FeOOH and iron oxides were major corrosion products, while β-Fe 8 O 8 (OH) 8 Cl 1.35 rather than β-FeOOH was formed when high chloride concentrations were provided. Chloride also suppressed the decreasing of corrosion rates, whereas increased the difficulty in the diffusion process by thickening the rust layers and transforming the rust compositions. Carbon steel is more susceptible to chloride attacks than ductile iron. The corrosion kinetics of ductile iron and carbon steel corresponded with the probabilistic and bilinear model respectively.

General notes on ductility in timber structures

NARCIS (Netherlands)

Jorissen, A.J.M.; Fragiacomo, M.

2011-01-01

The paper discusses the implications of ductility in design of timber structures under static and dynamic loading including earthquakes. Timber is a material inherently brittle in bending and in tension, unless reinforced adequately. However connections between timber members can exhibit significant

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.

Preliminary microstructural examination of high and low ductility type 316 creep rupture specimens

International Nuclear Information System (INIS)

Bolton, C.J.; Cordwell, J.E.; Hooper, A.J.; Marshall, P.; Steeds, J.; Wickens, A.

1977-09-01

A preliminary report is presented dealing with the examination of creep specimens from five casts of AISI Type 316 stainless steel which ruptured with variable ductility. Specimen microstructures and attempts to identify factors responsible for high or low creep ductility are discussed. (author)

Atomistic aspects of ductile responses of cubic silicon carbide during nanometric cutting.

Science.gov (United States)

Goel, Saurav; Luo, Xichun; Reuben, Robert L; Rashid, Waleed Bin

2011-11-11

Cubic silicon carbide (SiC) is an extremely hard and brittle material having unique blend of material properties which makes it suitable candidate for microelectromechanical systems and nanoelectromechanical systems applications. Although, SiC can be machined in ductile regime at nanoscale through single-point diamond turning process, the root cause of the ductile response of SiC has not been understood yet which impedes significant exploitation of this ceramic material. In this paper, molecular dynamics simulation has been carried out to investigate the atomistic aspects of ductile response of SiC during nanometric cutting process. Simulation results show that cubic SiC undergoes sp3-sp2 order-disorder transition resulting in the formation of SiC-graphene-like substance with a growth rate dependent on the cutting conditions. The disorder transition of SiC causes the ductile response during its nanometric cutting operations. It was further found out that the continuous abrasive action between the diamond tool and SiC causes simultaneous sp3-sp2 order-disorder transition of diamond tool which results in graphitization of diamond and consequent tool wear.

The effect of pre-deformation on the ductility of chromium

International Nuclear Information System (INIS)

Wadsack, R.; Pippan, R.; Schedler, B.

2002-01-01

Full text: Due to their low neutron-induced radioactivity chromium based materials are considered to be candidates as structure materials in fusion technology. Drawbacks for the application of these materials in industrial design are their brittleness at room temperature and their high Ductile to Brittle Transition Temperatures (DBTT). In this paper mechanical and fractographical investigations are presented of pure chromium (DUCROPUR) with a purity of about 99.97 % and the dispersion strengthened chromium alloy Cr 5 Fe 1 Y 2 O 3 (DUCROLLOY). The investigated specimens have been produced in a powder metallurgical route. They have been tested in the as HIPped condition (recrystallized) and after different pre-deformations. DUCROPUR and DUCROLLOY with as HIPped microstructures show in bending tests and tension tests brittle behavior at RT. Plastic deformations are obtained between 200 o C and 250 o C and above 400 o C, respectively. The K Q value of DUCROPUR increases from 12 MPam 1/2 at 290 o C up to a value of 500 MPam 1/2 at 320 o C. In spite of the large fracture toughness value at 320 o C the final fracture occurs again in a cleavage mode. DUCROLLOY shows up to 740 o C only a slight increase of fracture toughness with increasing temperature. An improvement in ductility and a significant increase in fracture strength have been induced by pre-deformation in tension, in bending, by Equal Channel Angular Extrusion (ECAE) and by Cyclic Channel Die Compression (CCDC). The developed microstructures of the samples have been investigated in the Scanning Electron Microscope (SEM) by means of different techniques. In order to determine the typical microstructure sizes Back Scattered Electrons (BSE) imaging has been applied. To differ if the boundaries are large or low angle boundaries the degree of misorientation has been determined with the Electron Back Scatter Diffraction (EBSD) method. (author)

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)

Fracture toughness for materials of low ductility

International Nuclear Information System (INIS)

Barzilay, S.; Karp, B.; Perl, M.

1998-05-01

The results of a survey of methods for evaluating fracture toughness characteristics for semi-brittle and brittle materials are presented in this report. These methods differ considerably from those used for ductile materials by the specimen configurations, the methodology of the experiments and by the problems occurring while using these methods. The survey yields several important findings A. It is possible to create steady state crack growth by cyclic loading in several semi-brittle materials. B. The need for pre-cracking is not yet clear, nevertheless it is recommended to evaluate fracture toughens with pre-cracked specimen. C. As crack length and ligament size may effect fracture toughness results it is necessary to define minimum specimen dimensions to avoid this effect. D. The specimen thickness hardly affects the fracture toughens. E. Loading rate for the test is not well defined. It is commonly accepted to end the test in one minute. F. The main mechanism that causes inelastic deformation in semi-brittle materials is related to the generation of micro-cracks

Strong, Ductile, and Thermally Stable bcc-Mg Nanolaminates.

Science.gov (United States)

Pathak, Siddhartha; Velisavljevic, Nenad; Baldwin, J Kevin; Jain, Manish; Zheng, Shijian; Mara, Nathan A; Beyerlein, Irene J

2017-08-15

Magnesium has attracted attention worldwide because it is the lightest structural metal. However, a high strength-to-weight ratio remains its only attribute, since an intrinsic lack of strength, ductility and low melting temperature severely restricts practical applications of Mg. Through interface strains, the crystal structure of Mg can be transformed and stabilized from a simple hexagonal (hexagonal close packed hcp) to body center cubic (bcc) crystal structure at ambient pressures. We demonstrate that when introduced into a nanocomposite bcc Mg is far more ductile, 50% stronger, and retains its strength after extended exposure to 200 C, which is 0.5 times its homologous temperature. These findings reveal an alternative solution to obtaining lightweight metals critically needed for future energy efficiency and fuel savings.

Probing the structure and mechanical properties of the graphite nodules in ductile cast irons via nano-indentation

DEFF Research Database (Denmark)

Andriollo, Tito; Fæster, Søren; Winther, Grethe

2018-01-01

Little is known today about the mechanical properties of the graphite nodules, despite the key influence these particles have on the performance of ductile cast irons. To address this issue, nano-indentation tests were performed on the cross-section of a nodule whose sub-surface morphology...

A program to qualify ductile cast iron for use as a containment material for type B transport cask

International Nuclear Information System (INIS)

Golliher, K.G.; Sorenson, K.B.; Witt, C.R.

1990-01-01

This paper reports on the Department of Energy (DOE) investigations for the use of ductile cast iron (DCI) as a candidate material for radioactive material transportation cask construction. The investigation will include materials testing and full-scale cask testing. The major effort will focus on materials qualification and cask evaluation of the 9 meter and puncture drop test events. Interaction by contract with the private industry, the American Society for Testing and Materials (ASTM) Committee A4.04, and the Electric Power Research Institute (EPRI) will be actively pursued to establish material specification acceptance criteria for ductile iron use as a cask material in the United States of America (USA). All test results will be documented in the safety analysis report for packaging for submission to the U.S. Nuclear Regulatory Commission (NRC). The goal of this program is a certificate of compliance for DCI from the NRC to transport high-level radioactive materials. The acceptance of DCI within the USA cask design community will offer an alternative to present-day materials for cask construction, and its entry has the potential of providing significant cost-savings

Nanowire failure: long = brittle and short = ductile.

Science.gov (United States)

Wu, Zhaoxuan; Zhang, Yong-Wei; Jhon, Mark H; Gao, Huajian; Srolovitz, David J

2012-02-08

Experimental studies of the tensile behavior of metallic nanowires show a wide range of failure modes, ranging from ductile necking to brittle/localized shear failure-often in the same diameter wires. We performed large-scale molecular dynamics simulations of copper nanowires with a range of nanowire lengths and provide unequivocal evidence for a transition in nanowire failure mode with change in nanowire length. Short nanowires fail via a ductile mode with serrated stress-strain curves, while long wires exhibit extreme shear localization and abrupt failure. We developed a simple model for predicting the critical nanowire length for this failure mode transition and showed that it is in excellent agreement with both the simulation results and the extant experimental data. The present results provide a new paradigm for the design of nanoscale mechanical systems that demarcates graceful and catastrophic failure. © 2012 American Chemical Society

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)

Analysis Strategy for Fracture Assessment of Defects in Ductile Materials

Energy Technology Data Exchange (ETDEWEB)

Dillstroem, Peter; Andersson, Magnus; Sattari-Far, Iradj; Weilin Zang (Inspecta Technology AB, Stockholm (Sweden))

2009-06-15

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

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

Tensile testing

CERN Document Server

2004-01-01

A complete guide to the uniaxial tensile test, the cornerstone test for determining the mechanical properties of materials: Learn ways to predict material behavior through tensile testing. Learn how to test metals, alloys, composites, ceramics, and plastics to determine strength, ductility and elastic/plastic deformation. A must for laboratory managers, technicians, materials and design engineers, and students involved with uniaxial tensile testing. Tensile Testing , Second Edition begins with an introduction and overview of the test, with clear explanations of how materials properties are determined from test results. Subsequent sections illustrate how knowledge gained through tensile tests, such as tension properties to predict the behavior (including strength, ductility, elastic or plastic deformation, tensile and yield strengths) have resulted in improvements in materals applications. The Second Edition is completely revised and updated. It includes expanded coverage throughout the volume on a variety of ...

Effect of Boron and Titanium Addition on the Hot Ductility of Low-Carbon Nb-Containing Steel

Science.gov (United States)

Liu, Wei-Jian; Li, Jing; Shi, Cheng-Bin; Huo, Xiang-Dong

2015-12-01

The effect of boron and titanium addition on the hot ductility of Nb-containing steel was investigated using hot tensile tests. The fracture surface and the quenched longitudinal microstructure were examined by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that both steel samples had the similar change from 1,100°C to 700°C. The hot ductility of Nb-containing steel with boron and titanium addition was higher than the steel without boron and titanium in the temperature range of 900-750°C. Because the formation of intergranular ferrite was inhibited by solute boron segregating on the grain boundary, the formation of TiN changed the distribution of Nb- and boron-containing precipitates and improved the amount of intragranular ferrite.

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.

Effect of Structure Factor on High-Temperature Ductility of Pipe Steels

Science.gov (United States)

Kolbasnikov, N. G.; Matveev, M. A.; Mishnev, P. A.

2016-05-01

Effects of various factors such as the grain size, the morphology of nonmetallic inclusions, and joint microalloying with boron and titanium on the high-temperature ductility of pipe steels are studied. Physical modeling of the conditions of cooling of the skin of a continuous-cast preform in the zone of secondary cooling in a Gleeble facility is performed. Technical recommendations are given for raising the hot ductility of steels under industrial conditions.

Determination of the initiation of ductile tearing in cracked branch pipes on the basis of a pre-determined criterion using small specimens

International Nuclear Information System (INIS)

Chapuliot, S.; Marie, S.

1999-01-01

This article describes an experimental and numerical study of the initiation conditions of ductile tearing in ferritic materials. An initial criterion J i is determined experimentally using a sufficiently thick CT specimen. The numerical and experimental aspects are then discussed for thinner CT specimen and a method is proposed for determining it in thin test samples. The local ductile tear initiation criterion, which was determined on the basis of 3D finite element calculations, was applied to a cracked branch pipe geometry subjected to out-of-plane bending to compare the load estimates at the start of propagation and the values measured during the test. The results of the comparison were highly satisfactory: the criterion is predictive. (orig.)

MIT miniaturized disk bend test

International Nuclear Information System (INIS)

Harling, O.K.; Lee, M.; Sohn, D.S.; Kohse, G.; Lau, C.W.

1983-01-01

A miniaturized disk bend test (MDBT) using transmission electron microscopy specimens for the determination of various mechanical properties is being developed at MIT. Recent progress in obtaining strengths and ductilities of highly irradiated metal alloys is reviewed. Other mechanical properties can also be obtained using the MDBT approach. Progress in fatigue testing and in determination of the ductile-to-brittle transition temperature is reviewed briefly. 11 figures

Plasticity of ductile metallic glasses: a self-organized critical state.

Science.gov (United States)

Sun, B A; Yu, H B; Jiao, W; Bai, H Y; Zhao, D Q; Wang, W H

2010-07-16

We report a close correlation between the dynamic behavior of serrated flow and the plasticity in metallic glasses (MGs) and show that the plastic deformation of ductile MGs can evolve into a self-organized critical state characterized by the power-law distribution of shear avalanches. A stick-slip model considering the interaction of multiple shear bands is presented to reveal complex scale-free intermittent shear-band motions in ductile MGs and quantitatively reproduce the experimental observations. Our studies have implications for understanding the precise plastic deformation mechanism of MGs.

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.

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 multi-scale correlative investigation of ductile fracture

International Nuclear Information System (INIS)

Daly, M.; Burnett, T.L.; Pickering, E.J.; Tuck, O.C.G.; Léonard, F.; Kelley, R.; Withers, P.J.; Sherry, A.H.

2017-01-01

The use of novel multi-scale correlative methods, which involve the coordinated characterisation of matter across a range of length scales, are becoming of increasing value to materials scientists. Here, we describe for the first time how a multi-scale correlative approach can be used to investigate the nature of ductile fracture in metals. Specimens of a nuclear pressure vessel steel, SA508 Grade 3, are examined following ductile fracture using medium and high-resolution 3D X-ray computed tomography (CT) analyses, and a site-specific analysis using a dual beam plasma focused ion beam scanning electron microscope (PFIB-SEM). The methods are employed sequentially to characterise damage by void nucleation and growth in one volume of interest, allowing for the imaging of voids that ranged in size from less than 100 nm to over 100 μm. This enables the examination of voids initiated at carbide particles to be detected, as well as the large voids initiated at inclusions. We demonstrate that this multi-scale correlative approach is a powerful tool, which not only enhances our understanding of ductile failure through detailed characterisation of microstructure, but also provides quantitative information about the size, volume fractions and spatial distributions of voids that can be used to inform models of failure. It is found that the vast majority of large voids nucleated at MnS inclusions, and that the volume of a void varied according to the volume of its initiating inclusion raised to the power 3/2. The most severe voiding was concentrated within 500 μm of the fracture surface, but measurable damage was found to extend to a depth of at least 3 mm. Microvoids associated with carbides (carbide-initiated voids) were found to be concentrated around larger inclusion-initiated voids at depths of at least 400 μm. Methods for quantifying X-ray CT void data are discussed, and a procedure for using this data to calibrate parameters in the Gurson-Tvergaard Needleman (GTN

Effects of neutron irradiation and fatigue on ductility of stainless steel DIN-1-4948

International Nuclear Information System (INIS)

de Vries, M.I.; van der Schaaf, B.; Staal, H.U.; Elen, J.D.

1978-01-01

Test specimens of stainless steel DIN 1.4948, which is similar to AISI Type 304, have been irradiated at 723 and 823 K up to fluences of 1*10$sup 23$ neutrons (n)*m$sup -2$ and 5*10$sup 24$ n*m$sup -2$ (E>0.1 MeV). These are representative conditions for the reactor vessel and inner components of the liquid metal fast breeder reactor SNR-300 after 16 years of operation. High-temperature (723 to 1023 K) tension tests at strain rates ($epsilon$) from 10$sup -7$ to 10 s$sup -1$ show a considerable decrease of tensile ductility. The extent depends on helium content, test temperature, and strain rate. The atomic helium fractions of 3*10$sup -7$ and 7*10$sup -6$ result from the reactions of thermal neutrons with the 14 ppm boron present in the steel. Helium embrittlement sets in at strain rates below 1 to 10 s$sup -1$ (the range of interest for Bethe-Tait accident analyses). A minimum total elongation value of 6 percent is shown at 923 K. The postirradiation fatigue life is reduced by up to about 50 percent due to intergranular cracking. The combination of irradiation and fatigue causes a decrease of ductility after a smaller number of prior fatigue cycles than in the case of unirradiated material. 8 refs

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

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.

Ductile damage evolution and strain path dependency

NARCIS (Netherlands)

Tasan, C.C.; Hoefnagels, J.P.M.; Peerlings, R.H.J.; Geers, M.G.D.; Horn, ten C.H.L.J.; Vegter, H.; Cueto, E.; Chinesta, F.

2007-01-01

Forming limit diagrams are commonly used in sheet metal industry to define the safe forming regions. These diagrams are built to define the necking strains of sheet metals. However, with the rise in the popularity of advance high strength steels, ductile fracture through damage evolution has also

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.)

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)

Enhancement of shear strength and ductility for reinforced concrete wide beams due to web reinforcement

Directory of Open Access Journals (Sweden)

M. Said

2013-12-01

Full Text Available The shear behavior of reinforced concrete wide beams was investigated. The experimental program consisted of nine beams of 29 MPa concrete strength tested with a shear span-depth ratio equal to 3.0. One of the tested beams had no web reinforcement as a control specimen. The flexure mode of failure was secured for all of the specimens to allow for shear mode of failure. The key parameters covered in this investigation are the effect of the existence, spacing, amount and yield stress of the vertical stirrups on the shear capacity and ductility of the tested wide beams. The study shows that the contribution of web reinforcement to the shear capacity is significant and directly proportional to the amount and spacing of the shear reinforcement. The increase in the shear capacity ranged from 32% to 132% for the range of the tested beams compared with the control beam. High grade steel was more effective in the contribution of the shear strength of wide beams. Also, test results demonstrate that the shear reinforcement significantly enhances the ductility of the wide beams. In addition, shear resistances at failure recorded in this study are compared to the analytical strengths calculated according to the current Egyptian Code and the available international codes. The current study highlights the need to include the contribution of shear reinforcement in the Egyptian Code requirements for shear capacity of wide beams.

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

Microstructure feature of friction stir butt-welded ferritic ductile iron

International Nuclear Information System (INIS)

Chang, Hung-Tu; Wang, Chaur-Jeng; Cheng, Chin-Pao

2014-01-01

Highlights: • Defect-free ferritic ductile iron joints is fabricated by FSW. • The welding nugget is composed of graphite, martensite, and recrystallized ferrite. • The graphite displays a striped pattern in the surface and advancing side. • The ferritic matrix transforms into martensite structure during welding. • High degree of plastic deformation is found on the advancing side. - Abstract: This study conducted friction stir welding (FSW) by using the butt welding process to join ferritic ductile iron plates and investigated the variations of microsturcture in the joined region formed after welding. No defects appeared in the resulting experimental weld, which was formed using a 3-mm thick ductile iron plate and tungsten carbide alloy stir rod to conduct FSW at a rotational speed of 982 rpm and traveling speed of 72 mm/min. The welding region was composed of deformed graphite, martensite phase, and dynamically recrystallized ferrite structures. In the surface region and on the advancing side (AS), the graphite displayed a striped configuration and the ferritic matrix transformed into martensite. On the retreating side (RS), the graphite surrounded by martensite remained as individual granules and the matrix primarily comprised dynamically recrystallized ferrite. After welding, diffusion increased the carbon content of the austenite around the deformed graphite nodules, which transformed into martensite during the subsequent cooling process. A micro Vickers hardness test showed that the maximum hardness value of the martensite structures in the weld was approximately 800 HV. An analysis using an electron probe X-ray microanalyzer (EPMA) indicated that its carbon content was approximately 0.7–1.4%. The peak temperature on the RS, 8 mm from the center of the weld, measured 630 °C by the thermocouple. Overall, increased severity of plastic deformation and process temperature near the upper stir zone (SZ) resulted in distinct phase transformation

Effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material

Science.gov (United States)

Zhu, J.; Zheng, W. Z.; Qin, C. Z.; Xu, Z. Z.; Wu, Y. Q.

2018-01-01

The effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material (AASCM) is studied. The research contents include: fiber type (plant fiber, polypropylene fiber), fiber content, mechanical property index, tensile stress-strain relationship curve, treating time. The test results showed that the compressive strength of two fibers reinforced AASCM was about 90 ~ 110MPa, and the tensile strength was about 3 ~ 5MPa. The reinforcement effect of polypropylene fiber is superior to that of plant fiber, and the mechanical properties of polypropylene fiber reinforced AASCM are superior to those of plant fiber, According to the comparison of SEM pictures, the plant fiber and polypropylene fiber are both closely bound with the matrix, and the transition zones are complete and close. Thus, it is proved that plant fiber and polypropylene fiber delay the crack extension and enhance the ductility of AASCM.

Implications of radiation-induced reductions in ductility to the design of austenitic stainless steel structures

International Nuclear Information System (INIS)

Lucas, G.E.; Billone, M.; Pawel, J.E.; Hamilton, M.L.

1995-01-01

In the dose and temperature range anticipated for ITER, austenitic stainless steels exhibit significant hardening with a concomitant loss in work hardening and uniform elongation. However, significant post-necking ductility may still be retained. When uniform elongation (e u ) is well defined in terms of a plastic instability criterion, e u is found to sustain reasonably high values out to about 7 dpa in the temperature range 250-350 C, beyond which it decreases to about 0.3% for 316LN. This loss of ductility has significant implications to fracture toughness and the onset of new failure modes associated with hear instability. However, the retention of a significant reduction in area at failure following irradiation indicates a less severe degradation of low-cycle fatigue life in agreement with a limited amount of data obtained to date. Suggestions are made for incorporating these results into design criteria and future testing programs

Ductile shear failure or plug failure of spot welds modelled by modified Gurson model

DEFF Research Database (Denmark)

Nielsen, Kim Lau; Tvergaard, Viggo

2010-01-01

For resistance spot welded shear-lab specimens, interfacial failure under ductile shearing or ductile plug failure are analyzed numerically, using a shear modified Gurson model. The interfacial shear failure occurs under very low stress triaxiality, where the original Gurson model would predict...

Parametric study of irradiation effects on the ductile damage and flow stress behavior in ferritic-martensitic steels

International Nuclear Information System (INIS)

Chakraborty, Pritam; Biner, S.Bulent

2015-01-01

Ferritic-martensitic steels are currently being considered as structural materials in fusion and Gen-IV nuclear reactors. These materials are expected to experience high dose radiation, which can increase their ductile to brittle transition temperature and susceptibility to failure during operation. Hence, to estimate the safe operational life of the reactors, precise evaluation of the ductile to brittle transition temperatures of ferritic-martensitic steels is necessary. Owing to the scarcity of irradiated samples, particularly at high dose levels, micro-mechanistic models are being employed to predict the shifts in the ductile to brittle transition temperatures. These models consider the ductile damage evolution, in the form of nucleation, growth and coalescence of voids; and the brittle fracture, in the form of probabilistic cleavage initiation, to estimate the influence of irradiation on the ductile to brittle transition temperature. However, the assessment of irradiation dependent material parameters is challenging and influences the accuracy of these models. In the present study, the effects of irradiation on the overall flow stress and ductile damage behavior of two ferritic-martensitic steels is parametrically investigated. The results indicate that the ductile damage model parameters are mostly insensitive to irradiation levels at higher dose levels though the resulting flow stress behavior varies significantly.

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.

Gradient twinned 304 stainless steels for high strength and high ductility

Energy Technology Data Exchange (ETDEWEB)

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

2016-06-14

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

Microstructural basis and crack growth theories for post-irradiation ductility loss in Nimonic PE16

International Nuclear Information System (INIS)

Chang, A.L.

1982-01-01

A study has been carried out to investigate the degradation of postirradiation ductility at reactor temperatures in Nimonic PE16, a Fe-Cr-Ni-based precipitation-hardened superalloy. Fractographic and microstructural investigations show that the grain matrix is capable of deformation and does not limit the postirradiation tensile ductility. Grain-boundary helium bubbles formed during neutron irradiation seem to be crack nucleation sites under stress. Growth and coalescence of these microcracks under stress lead to intergranular fracture. A rigid-grain fracture model is shown to be able to correlate the observed microstructures with most features of the mechanical properties, except the strain rate dependence of the ductility. By incorporating the interactions between diffusion and plastic deformation, a plastic-grain fracture model has been developed which can explain all postirradiation tensile ductility data quantitatively. 13 references

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.

Development of ductile long-range ordered alloys for fusion reactor systems

International Nuclear Information System (INIS)

Liu, C.T.

1979-01-01

A series of Fe-base ordered alloys with compositions (Fe,Ni,Co) 3 V are developed for fusion reactor applications. The alloys from cubic ordered structure similar to AuCu 3 below their critical ordering temperature. The alloys in the ordered state are ductile with elongation in excess of 35% at room temperture. Tensile tests of the ordered alloys at elevated temperatures indicate an unusually attractive mechanical behavior. Their strength, instead of decreasing as with conventional alloys, increases with temperature because of ordering effects. As a result, the ordered alloys are much stronger than 316 stainless steel, particularly at elevated temperatures

Enhanced ductility of surface nano-crystallized materials by modulating grain size gradient

International Nuclear Information System (INIS)

Li, Jianjun; Soh, A K

2012-01-01

Surface nano-crystallized (SNC) materials with a graded grain size distribution on their surfaces have been attracting increasing scientific interest over the past few decades due to their good synergy of high strength and high ductility. However, to date most of the existing studies have focused on the individual contribution of three different aspects, i.e. grain size gradient (GSG), work-hardened region and surface compressive residual stresses, which were induced by surface severe plastic deformation processes, to the improved strength of SNC materials as compared with that of their coarse grained (CG) counterparts. And the ductility of these materials has hardly been studied. In this study, a combination of theoretical analysis and finite element simulations was used to investigate the role of GSG in tuning the ductility of SNC materials. It was found that the ductility of an SNC material can be comparable to that of its CG counterpart, while it simultaneously possessed a much higher strength than its CG core if the optimal GSG thickness and grain size of the topmost phase were adopted. A design map that can be used as a guideline for fabrication of SNC materials was also plotted. Our predictions were also compared with the corresponding experimental results. (paper)

Improved ductility of Ni3Si by microalloying with boron or carbon

International Nuclear Information System (INIS)

Taub, A.I.; Briant, C.L.

1989-01-01

The effects of boron and carbon additions on the tendency for intergranular fracture in trinickel silicide intermetallics are reported. Melt spinning of Ni 77 Si 23 alloyed with 0.1 at. pct boron results in full bend ductility and complete transgranular fracture compared with brittle intergranular fracture for the unmodified compound. Alloying with 0.1 at. pct carbon also produced full bend ductility but a mixed mode failure (30 pct transgranular). For both carbon and boron additions, reducing the Ni concentration of the base compound results in a greater percentage of intergranular fracture. For Ni 77 Si 23 , the solubility limit is between 0.1 and 0.2 t. pct boron. For compounds with silicon concentrations of 23.5 and 24.0 at. pct, the solubility limit is less than 0.1 at. pct boron. Boron additions above the solubility limit result in Ni 3 B precipitates which degrade the bend ductility and increase the percentage of intergranular fracture. Alloying with carbon above the solubility limit ( 77 Si 23 , increasing the carbon concentration from 0.1 to 1.0 at. pct resulted in no change in the ductility. Auger examination of the grain boundary composition showed strong segregation of both boron and carbon. Enrichment in silicon concentration was also observed

Microstructure and ductility of Fe28Cr16Co alloy with additions of silicon, molybdenum, titanium and aluminium

International Nuclear Information System (INIS)

Vodopivec, F.; Zvokelj, J.; Breskvar, B.; Gnidovec, D.; Rodic, A.; Torkar, M.

1994-01-01

The microstructure of several alloys with base composition Fe28Cr16Co and addition up to 1.5% silicon, 0.32% titanium, 2.34% molybdenum and 1% aluminium was investigated in the temperature range 500 to 1250 C by optical microscopy, hardness measurements and dilatometry. Also, ductility and wire drawing tests were carried out on some alloys. The addition of silicon, titanium, molybdenum or 0.13% Al does not prevent the formation of γ phase up to the temperature 1250 C and the formation of phase σ in the temperature range 700 to approximately 1000 C. The addition of 1% Al prevents the formation of phase σ and shifts the temperature of formation of phase γ to 1158 C. The addition of different elements does not affect significantly the spinodal decomposition of phase α. At increased temperature an interval of sufficient ductility for deformation by wire drawing was established. The ductility was greatly improved if the microstructure consisted of small inclusions of phase γ in a matrix of phase α, probably because the deformation by twinning was hindered. However, insufficient magnetic properties were obtained also after 80% of deformation. (orig.)

A variational void coalescence model for ductile metals

KAUST Repository

Siddiq, Amir; Arciniega, Roman; El Sayed, Tamer

2011-01-01

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

Disk-bend ductility tests for irradiated materials

International Nuclear Information System (INIS)

Klueh, R.L.; Braski, D.N.

1984-01-01

We modified the HEDL disk-bend test machine and are using it to qualitatively screen alloys that are susceptible to embrittlement caused by irradiation. Tests designed to understand the disk-bend test in relation to a uniaxial test are discussed. Selected results of tests of neutron-irradiated material are also presented

Geological ductile deformation mapping at the Olkiluoto site, Eurajoki, Finland

Energy Technology Data Exchange (ETDEWEB)

Engstroem, J. [Geological Survey of Finland, Espoo (Finland)

2013-12-15

During 2010-2012 eight larger excavated and cleaned outcrops were investigated to study the polyphase nature of the ductile deformation within the Olkiluoto Island. A detailed structural geological mapping together with a thin section study was performed to get a broader and better understanding of the nature and occurrence of these different ductile deformation phases. These outcrops were selected to represent all different ductile deformation phases recognized earlier during the site investigations. The relicts of primary sedimentary structures and products of the earliest deformations (D{sub 0}-D{sub 1}) are mostly obscured by later deformation events. The D{sub 2}-D{sub 4} is the most significant ductile deformation phases occurring on the Olkiluoto Island and almost all structural features can be labeled within these three phases. The outcrops for this investigation were selected mostly from the eastern part of the Olkiluoto Island because that part of the Island has been less investigated previously. As a reference, one outcrop was selected in the western part of the Island where it was previously known that this location had especially well preserved structures of the second deformation phase (D{sub 2}). The S{sub 2} foliation is E-W orientated with moderate dip towards south. A few folds can be associated with this deformational event, mostly having a tight to isoclinal character. During D{sub 3} the migmatites were re-deformed and migrated leucosomes, were intruded mainly parallel to S{sub 3} axial surfaces having a NE-SW orientation. Generally the dip of the S{sub 3} axial surfaces is slightly more steeper (55- 65 deg C) than that of the S{sub 2} axial surfaces, which shows a more moderate dip (40-65 deg C). F{sub 3} fold structures are quite common in the eastern part of Island showing asymmetrical, overturned, shear folds usually with a dextral sense of shear. Large scale D{sub 3} shear structures contain blastomylonites as characteristic fault rocks

Prediction of fracture initiation in square cup drawing of DP980 using an anisotropic ductile fracture criterion

Science.gov (United States)

Park, N.; Huh, H.; Yoon, J. W.

2017-09-01

This paper deals with the prediction of fracture initiation in square cup drawing of DP980 steel sheet with the thickness of 1.2 mm. In an attempt to consider the influence of material anisotropy on the fracture initiation, an uncoupled anisotropic ductile fracture criterion is developed based on the Lou—Huh ductile fracture criterion. Tensile tests are carried out at different loading directions of 0°, 45°, and 90° to the rolling direction of the sheet using various specimen geometries including pure shear, dog-bone, and flat grooved specimens so as to calibrate the parameters of the proposed fracture criterion. Equivalent plastic strain distribution on the specimen surface is computed using Digital Image Correlation (DIC) method until surface crack initiates. The proposed fracture criterion is implemented into the commercial finite element code ABAQUS/Explicit by developing the Vectorized User-defined MATerial (VUMAT) subroutine which features the non-associated flow rule. Simulation results of the square cup drawing test clearly show that the proposed fracture criterion is capable of predicting the fracture initiation with sufficient accuracy considering the material anisotropy.

Improved ductility and oxidation resistance of cast Ti–6Al–4V alloys by microalloying

International Nuclear Information System (INIS)

Luan, J.H.; Jiao, Z.B.; Chen, G.; Liu, C.T.

2014-01-01

Highlights: • Modified Ti64 alloys with improved ductility and oxidation resistance are developed. • B improves the ductility by refining grain size and enhancing boundary cohesion. • Y enhances the oxidation resistance by possibly slowing down the oxidation kinetics. - Abstract: The effects of B and Y on the mechanical properties and oxidation behavior of cast Ti–6Al–4V alloys were systematically investigated, and the new alloys with improved ductility and oxidation resistance are developed by the microalloying approach. The results indicate that boron is beneficial for improving the ductility by not only grain-size refinement but also grain-boundary enhancement, while yttrium is effective in increasing the oxidation resistance through possibly slowing down the oxidation kinetics. The improved properties, together with their high strength, make the microalloyed cast Ti–6Al–4V alloys competitive for practical engineering applications

A new approach to ductile tearing assessment of pipelines under large-scale yielding

Energy Technology Data Exchange (ETDEWEB)

Ostby, Erling [SINTEF Materials and Chemistry, N-7465, Trondheim (Norway)]. E-mail: Erling.Obstby@sintef.no; Thaulow, Christian [Norwegian University of Science and Technology, N-7491, Trondheim (Norway); Nyhus, Bard [SINTEF Materials and Chemistry, N-7465, Trondheim (Norway)

2007-06-15

In this paper we focus on the issue of ductile tearing assessment for cases with global plasticity, relevant for example to strain-based design of pipelines. A proposal for a set of simplified strain-based driving force equations is used as a basis for calculation of ductile tearing. We compare the traditional approach using the tangency criterion to predict unstable tearing, with a new alternative approach for ductile tearing calculations. A criterion to determine the CTOD at maximum load carrying capacity in the crack ligament is proposed, and used as the failure criterion in the new approach. Compared to numerical reference simulations, the tangency criterion predicts conservative results with regard to the strain capacity. The new approach yields results in better agreement with the reference numerical simulations.

Numerical modelling of solidification of thin walled hypereutectic ductile cast iron

DEFF Research Database (Denmark)

Pedersen, Karl Martin; Hattel, Jesper; Tiedje, Niels

2006-01-01

Numerical simulation of solidification of ductile cast iron is normally based on a model where graphite nodules are surrounded by an austenite shell. The two phases are then growing as two concentric spheres governed by diffusion of carbon through the austenite shell. Experiments have however shown...... simulation of thin-walled ductile iron castings. Simulations have been performed with a 1-D numerical solidi¬fication model that includes the precipitation of non-eutectic austenite during the eutectic stage. Results from the simulations have been compared with experimental castings with wall thick...

Draft ASME code case on ductile cast iron for transport packaging

International Nuclear Information System (INIS)

Saegusa, T.; Arai, T.; Hirose, M.; Kobayashi, T.; Tezuka, Y.; Urabe, N.; Hueggenberg, R.

2004-01-01

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

Ductility and microstructure of precipitation-strengthened alloys irradiated in HFIR

International Nuclear Information System (INIS)

Yang, W.J.S.; Hamilton, M.L.

1983-08-01

Six γ' and γ'/γ'' strengthened Ni-base alloys have shown near-zero ductility after irradiation at 300 to 600 0 C in HFIR to a peak exposure of 9 dpa. Microstructural examination of the irradiated specimens showed that the loss of ductility in these alloys arises from the simultaneous existence of a strong matrix and weak grain boundaries. The strong matrix is attributed to the irradiation-induced γ' and γ'/γ'' precipitates, the faulted loops and a high density of fine helium bubbles. The weak grain boundaries are attributed to the formation of an unfavorable precipitate, such as eta-plates, recrystallized grains, a thin layer of γ' and helium bubbles

The MIT miniaturized disk bend test

International Nuclear Information System (INIS)

Harling, O.K.; Lee, M.; Sohn, D.S.; Kohse, G.; Lau, C.W.

1983-01-01

A miniaturized disk bend test (MDBT) using transmission electron microscopy specimens for the determination of various mechanical properties is being developed at MIT. Recent progress in obtaining strengths and ductilities of highly irradiated metal alloys is reviewed. Possibilities exist for applying the MDBT approach to the determination of other mechanical properties. Progress in fatigue testing and in determination of the ductile-to-brittle transition temperature is reviewed briefly

Effect of Tin, Copper and Boron on the Hot Ductility of 20CrMnTi Steel between 650 °C and 1100 °C

Science.gov (United States)

Peng, Hong-bing; Chen, Wei-qing; Chen, Lie; Guo, Dong

2015-02-01

The hot ductility of 20CrMnTi steel with x% tin, y% copper and z ppm boron (x = 0, 0.02; y = 0, 0.2; z = 0, 60) was investigated. The results show that tin and copper in 20CrMnTi steel are detrimental to its hot ductility while adding boron can eliminate the adverse effect and enhance hot ductility greatly. Tin is found to segregate to the boundaries tested by EPMA in 20CrMnTi steel containing tin and copper and tin-segregation is suppressed by adding boron, moreover, copper was found not to segregate to boundaries, however, fine copper sulfide was found from carbon extraction replicas using TEM. The adverse effect of tin and copper on the hot ductility was due mainly to tin segregation and fine copper sulfide in the steel. The proeutectoid ferrite film precipitating along the austenite grain boundary causes the ductility trough of the three examined steels. Tin and copper in 20CrMnTi steel can retard the occurrence of dynamic recrystallization (DRX) while boron-addition can compensate for that change. The beneficial effect of boron on 20CrMnTi steel containing tin and copper might be ascribed to the fact that boron segregates to grain boundaries, accelerates onset of DRX, retards austenite/ferrite transformation and promotes intragranular nucleation of ferrite.

Potentially exploitable supercritical geothermal resources in the ductile crust

Science.gov (United States)

Watanabe, Noriaki; Numakura, Tatsuya; Sakaguchi, Kiyotoshi; Saishu, Hanae; Okamoto, Atsushi; Ingebritsen, Steven E.; Tsuchiya, Noriyoshi

2017-01-01

The hypothesis that the brittle–ductile transition (BDT) drastically reduces permeability implies that potentially exploitable geothermal resources (permeability >10−16 m2) consisting of supercritical water could occur only in rocks with unusually high transition temperatures such as basalt. However, tensile fracturing is possible even in ductile rocks, and some permeability–depth relations proposed for the continental crust show no drastic permeability reduction at the BDT. Here we present experimental results suggesting that the BDT is not the first-order control on rock permeability, and that potentially exploitable resources may occur in rocks with much lower BDT temperatures, such as the granitic rocks that comprise the bulk of the continental crust. We find that permeability behaviour for fractured granite samples at 350–500 °C under effective confining stress is characterized by a transition from a weakly stress-dependent and reversible behaviour to a strongly stress-dependent and irreversible behaviour at a specific, temperature-dependent effective confining stress level. This transition is induced by onset of plastic normal deformation of the fracture surface (elastic–plastic transition) and, importantly, causes no ‘jump’ in the permeability. Empirical equations for this permeability behaviour suggest that potentially exploitable resources exceeding 450 °C may form at depths of 2–6 km even in the nominally ductile crust.

Experimental observation of dynamic ductile damage development under various triaxiality conditions - description of the principle

Directory of Open Access Journals (Sweden)

Pillon L.

2012-08-01

Full Text Available The Gurson model has been extended by Perrin to describe damage evolution in ductile viscoplastic materials. The so-called Gurson-Perrin model allows representing damage development with respect to strain-rate conditions. In order to fill a lack in current experimental procedures, we propose an experimental project able to test and validate the Gurson-Perrin model under various dynamic conditions and for different stress triaxiality levels.

X-ray diffraction study of the phase purity, order and texture of ductile B2 intermetallics

Energy Technology Data Exchange (ETDEWEB)

Mulay, R.P.; Wollmershauser, J.A.; Heisel, M.A. [Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904-4745 (United States); Bei, H. [Oak Ridge National Laboratory, Material Science and Technology Division, Oak Ridge, TN 37831 (United States); Russell, A.M. [Iowa State University, Department of Materials Science and Engineering, Ames, IA 50011 (United States); Agnew, S.R., E-mail: sra4p@virginia.edu [Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904-4745 (United States)

2010-04-15

Representatives (AgY, CuY, AgEr, CuDy, MgY and MgCe) of the newly discovered family of ductile stoichiometric B2 intermetallic (metal-rare-earth element, MR) compounds were characterized by X-ray diffraction, to determine if their anomalous ductility is related to an exceptional level of phase purity, lack of chemical ordering or a strong crystallographic texture. Brittle NiAl served as an anti-type in this study. We found that all of the rare-earth compounds, except MgY, have a significant volume fraction ({approx}5-20 vol.%) of second phases (M{sub 2}R intermetallics and R{sub 2}O{sub 3} oxides), which has not been reported in previous studies of these materials. The most ductile of observed MR compounds, AgY, is highly ordered. A moderate texture was observed in AgY, which may explain its higher ductility (using polycrystal modeling) as compared to other MR compounds. However, the intrinsic polycrystalline ductility of these compounds in the randomly textured state (like that observed in CuY) still has no specific, definitive explanation.

X-ray diffraction study of the phase purity, order and texture of ductile B2 intermetallics

International Nuclear Information System (INIS)

Mulay, R.P.; Wollmershauser, J.A.; Heisel, M.A.; Bei, H.; Russell, A.M.; Agnew, S.R.

2010-01-01

Representatives (AgY, CuY, AgEr, CuDy, MgY and MgCe) of the newly discovered family of ductile stoichiometric B2 intermetallic (metal-rare-earth element, MR) compounds were characterized by X-ray diffraction, to determine if their anomalous ductility is related to an exceptional level of phase purity, lack of chemical ordering or a strong crystallographic texture. Brittle NiAl served as an anti-type in this study. We found that all of the rare-earth compounds, except MgY, have a significant volume fraction (∼5-20 vol.%) of second phases (M 2 R intermetallics and R 2 O 3 oxides), which has not been reported in previous studies of these materials. The most ductile of observed MR compounds, AgY, is highly ordered. A moderate texture was observed in AgY, which may explain its higher ductility (using polycrystal modeling) as compared to other MR compounds. However, the intrinsic polycrystalline ductility of these compounds in the randomly textured state (like that observed in CuY) still has no specific, definitive explanation.

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

OpenAIRE

Dahmen, M.

2015-01-01

Ultra-high strength and supra-ductile are entering fields of new applications. Those materials are excellent candidates for modern light-weight construction and functional integration. As ultra-high strength steels the stainless martensitic grade 1.4034 and the bainitic steel UNS 53835 are investigated. For the supra-ductile steels stand two high austenitic steels with 18 and 28 % manganese. As there are no processing windows an approach from the metallurgical base on is required. Adjusting t...

Thermal distortion of disc-shaped ductile iron castings in vertically parted moulds

DEFF Research Database (Denmark)

Vedel-Smith, Nikolaj Kjelgaard; Rasmussen, Jakob; Tiedje, Niels Skat

2015-01-01

A disc-shaped casting with an inner boss and an outer rim, separated by a thin walled section, was examined. This measurable deformation varied with the feeding modulus. The influence of alloy composition, particularly Si content, was examined with a pearlitic ductile iron (EN-GJS-500-7) and a fu......A disc-shaped casting with an inner boss and an outer rim, separated by a thin walled section, was examined. This measurable deformation varied with the feeding modulus. The influence of alloy composition, particularly Si content, was examined with a pearlitic ductile iron (EN-GJS-500......-7) and a fully ferritic ductile iron (EN-GJS-450-10). The experiment showed that both the alloy composition and choice of feeder influenced the degreeof deformation measured in the finished casting. It was found that the deformation of the pearlitic alloy was influenced controllably by changing the feeder...

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

Science.gov (United States)

Dahmen, Martin

2015-03-01

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

New aspects about reduced LCF-life time of spherical ductile cast iron due to dynamic strain aging at intermediate temperatures

International Nuclear Information System (INIS)

Mouri, Hayato; Wunderlich, Wilfried; Hayashi, Morihito

2009-01-01

Spherical ductile cast iron (FCD400) is widely used as container material in nuclear energy processing line due to its superior mechanical properties and low price. Fatigue properties in low cycle fatigue (LCF) can be described well by the Manson-Coffin-Basquin's rule. However, at intermediate temperature range between 453 and 723 K the elongation-temperature-diagram shows a significantly 20-10% reduced elongation and an increase in yield stress in tensile test experiments. These non-linear deviations and the phenomenon of less ductility at intermediate temperatures are known for a long time [K. Chijiiwa, M. Hayashi, Mechanical properties of ductile cast iron at temperature in the region of room temperature to liquid, Imono 51 (7) (2004) 395-400]. But the following explanation is presented for the first time. In the same temperature range as the reduced fatigue life time dynamic strain ageing (DSA) also known as Portevin-le-Chartelier effect with the formation of visible serrations occurs. Both phenomena are explained by interaction effects between carbon diffusion and dislocation velocity which have at this temperature the same order of magnitude. However, this phenomenon shows interesting behavior at intermediate temperature range. During the low cycle fatigue test, DSA phenomenon disappeared, but mechanical properties show clear evidence of DSA phenomenon. Therefore, the purpose of this paper is to study the correlation of DSA occurrence, LCF and mechanical properties.

An analytical model for the ductile failure of biaxially loaded type 316 stainless steel subjected to thermal transients

International Nuclear Information System (INIS)

Dimelfi, R.J.

1987-01-01

Failure properties are calculated for the case of biaxially loaded type 316 stainless steel tubes that are heated from 300 K to near melting at various constant rates. The procedure involves combining a steady state plastic-deformation rate law with a strain hardening equation. Integrating under the condition of plastic instability gives the time and plastic strain at which ductile failure occurs for a given load. The result is presented as an analytical expression for equivalent plastic strain as a function of equivalent stress, temperature, heating rate and material constants. At large initial load, ductile fracture is calculated to occur early, at low temperatures, after very little deformation. At very small loads deformation continues for a long time to high temperatures where creep rupture mechanisms limit ductility. In the case of intermediate loads, the plastic strain accumulated before the occurrence of unstable ductile fracture is calculated. Comparison of calculated results is made with existing experimental data from pressurized tubes heated at 5.6 K/s and 111 K/s. When the effect of grain growth on creep ductility is taken into account from recrystallization data, agreement between measured and calculated uniform ductility is excellent. The general reduction in ductility and failure time that is observed at higher heating rate is explained via the model. The model provides an analytical expression for the ductility and failure time during transients for biaxially loaded type 316 stainless steel as a function of the initial temperature and load, as well as the material creep and strain hardening parameters. (orig.)

Microstructure vs. Near-threshold Fatigue Crack Growth Behavior of an Heat-treated Ductile Iron

Directory of Open Access Journals (Sweden)

Radomila KONEČNÁ

2012-03-01

Full Text Available Perferritic isothermal ductile iron (IDI® is an intermediate grade between the low-strength grades of austempered ductile iron (ADI and pearlitic ductile iron (DI recently developed by Zanardi Fonderie Italy. IDI is produced by heat-treating an unalloyed nodular cast iron. The specific matrix microstructure is called “Perferritic” and consists predominantly of ferrite and pearlite. Compared to the pearlitic grades of nodular ductile iron, IDI combines similar strength with higher toughness as a result of the isothermal heat treatment. In this contribution the fatigue crack growth resistance and Kath of IDI are investigated and correlated to mechanical properties and microstructural features. The threshold Ka was determined using the load shedding technique as per ASTM Standard E-647 using CT specimens extracted from a cast block. Tensile specimens were extracted from the broken CT halves and used to determine the static mechanical properties. A metallographic investigation was carried out to correlate structural features and mechanical properties.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1336

Hydride-induced degradation of hoop ductility in textured zirconium-alloy tubes: A theoretical analysis

International Nuclear Information System (INIS)

Qin, W.; Szpunar, J.A.; Kozinski, J.

2012-01-01

Hydride-induced degradation of hoop ductility in Zr-alloy tubular components has been studied for many years because of its importance in the nuclear industry. In this paper the role of intergranular and intragranular δ-hydrides in the degradation of ductility of the textured Zr-alloy tubes is investigated. The correlation among hydride distribution, orientation and morphology in the tubes is formulated based on thermodynamic modeling, and then analyzed. The results show that the applied stress, the crystallographic texture of α-Zr matrix, the grain-boundary structure, and the morphology and size of Zr grains simultaneously govern the site preference and the orientation of hydrides. A criterion is proposed to determine the threshold stress of hydride reorientation. The hoop ductility of the hydrided Zr tubes is discussed using the concept of macroscopic fracture strain. It is shown that the intergranular hydrides may be more deleterious to ductility than the intragranular ones. This work defines a general framework for understanding the relation of the microstructure of hydride-forming materials to embrittlement.

Strong, Ductile Rotor For Cryogenic Flowmeters

Science.gov (United States)

Royals, W. T.

1993-01-01

Improved magnetic flowmeter rotor resists cracking at cryogenic temperatures, yet provides adequate signal to magnetic pickup outside flowmeter housing. Consists mostly of stainless-steel alloy 347, which is ductile and strong at low temperatures. Small bead of stainless-steel alloy 410 welded in groove around circumference of round bar of stainless-steel alloy 347; then rotor machined from bar. Tips of rotor blades contain small amounts of magnetic alloy, and passage of tips detected.

Micromechanisms of ductile stable crack growth in nuclear pressure vessel steels

Energy Technology Data Exchange (ETDEWEB)

Belcher, W.P.A.; Druce, S.G.

1981-10-01

The objective of this work was to investigate the relationship between the micromechanisms of ductile crack growth, the microstructural constituent phases present in nuclear pressure vessel steel, and the observed fracture behavior as determined by impact and fracture mechanics tests. Results from a microstructural and mechanical property comparison of an A508 Class 3 pressurized water reactor nozzle forging cutout and a 150-mm-thick A533B Class 1 plate are reported. The variation of upper-shelf toughness between the two steels and its orientation sensitivity are discussed on the basis of inclusion and precipitate distributions. Inclusion clusters in A533B, deformed to elongated disks in the rolling plane, have a profound effect on short transverse fracture properties. Data derived using the multi-specimen J-integral method to characterize the initiation of ductile crack extension and resistance to stable crack growth are compared with equivalent Charpy results. Results of the J /SUB R/ -curve analyses indicate (1) that the A533B short transverse crack growth resistance is approximately half that observed from transverse and longitudinal specimen orientations, and (2) that the A508 initiation toughness and resistance to stable crack growth are insensitive to position through the forging wall, and are higher than exhibited by A533B at any orientation in the midthickness position.

Ductile failure simulation of tensile plates with multiple through-wall cracks

International Nuclear Information System (INIS)

Kim, Nak Hyun; Oh, Chang Sik; Kim, Yun Jae

2009-01-01

In this paper, failure behaviors of ductile plates with multiple cracks are simulated, finite element analyses using ABAQUS. To simulate crack coalescence or propagation of multiple cracks, a technique to reduce stresses within an finite element is proposed and implemented using user-defined subroutines provided in ABAQUS. In the proposed method, all stress components reduce to almost zero when the effective strain reaches critical values which are a function of the stress triaxiality. A main benefit of the proposed numerical scheme is its simplicity. The proposed scheme is applied to simulate multiple-cracked plate tests by Japanese researchers. Simulated maximum loads are compared with experimental ones, showing overall good agreements.

Effects of various austempering temperatures on fatigue properties in ductile iron

International Nuclear Information System (INIS)

Salman, S.; Findik, F.; Topuz, P.

2007-01-01

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

On the influence of microscale inertia on dynamic ductile crack extension

Science.gov (United States)

Jacques, N.; Mercier, S.; Molinari, A.

2012-08-01

The present paper is devoted to the modelling of damage by micro-voiding in ductile solids under dynamic loading conditions. Using a dynamic homogenization procedure, a constitutive damage model accounting for inertial effects due to void growth (microscale inertia or micro-inertia) has been developed. The role played by microscale inertia in dynamic ductile crack growth is investigated with the use of the proposed micromechanical modelling. It is found that micro-inertia has a significant influence on the fracture behaviour. Micro-inertia limits the velocity at which cracks propagate. It also contributes to increase the apparent dynamic toughness of the material.

Studies of void growth in a thin ductile layer between ceramics

DEFF Research Database (Denmark)

Tvergaard, Viggo

1997-01-01

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...... 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....

Ductility of a 60-Story Shearwall Frame-Belt Truss (Virtual Outrigger Building

Directory of Open Access Journals (Sweden)

Pudjisuryadi P.

2012-01-01

Full Text Available Researches have been conducted to study Shearwall-frame combined with belt truss as structural system (SFBT, in which the post-elastic behavior and ductility of this structural system are explored. A 60-story SFBT building, with a ductility set equal to 3.75 (value for fully ductile cantilever wall is considered. The Elastic Response Spectrum used for design is taken from Zone 2 of Indonesian Seismic Map. Capacity design method according to Indonesian Concrete Code is employed. The seismic performance is analyzed using static non-linear push-over analysis and dynamic non-linear time-history analysis. Spectrum consistent ground motions of the May 18, 1940 El-Centro earthquake N-S components scaled to maximum accelerations of various return periods (50, 200, and 500 years are used for analysis. The results of this study show that plastic hinges mainly developed in beams above the truss, columns below the truss, and bottom levels of the wall. The building shows no indication of structural instability.

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.

Prediction of microstructure and ductile damage of a high-speed railway axle steel during cross wedge rolling

OpenAIRE

Huo, Y; Lin, J; Bai, Q; Wang, B; Tang, X; Ji, H

2016-01-01

Microstructure and ductile damage have a significant influence on the deformation behavior of high-speed railway axles during hot cross wedge rolling (CWR) and its final performance. In this study, based on the continuum damage mechanics, a multiaxial constitutive model coupling microstructure and ductile damage was established to predict the evolution of microstructure and ductile damage of 25CrMo4 during hot CWR processes. Material constants within the multiaxial constitutive model were det...

Dislocation Strengthening without Ductility Trade-off in Metastable Austenitic Steels

Science.gov (United States)

Liu, Jiabin; Jin, Yongbin; Fang, Xiaoyang; Chen, Chenxu; Feng, Qiong; Liu, Xiaowei; Chen, Yuzeng; Suo, Tao; Zhao, Feng; Huang, Tianlin; Wang, Hongtao; Wang, Xi; Fang, Youtong; Wei, Yujie; Meng, Liang; Lu, Jian; Yang, Wei

2016-10-01

Strength and ductility are mutually exclusive if they are manifested as consequence of the coupling between strengthening and toughening mechanisms. One notable example is dislocation strengthening in metals, which invariably leads to reduced ductility. However, this trend is averted in metastable austenitic steels. A one-step thermal mechanical treatment (TMT), i.e. hot rolling, can effectively enhance the yielding strength of the metastable austenitic steel from 322 ± 18 MPa to 675 ± 15 MPa, while retaining both the formability and hardenability. It is noted that no boundaries are introduced in the optimized TMT process and all strengthening effect originates from dislocations with inherited thermal stability. The success of this method relies on the decoupled strengthening and toughening mechanisms in metastable austenitic steels, in which yield strength is controlled by initial dislocation density while ductility is retained by the capability to nucleate new dislocations to carry plastic deformation. Especially, the simplicity in processing enables scaling and industrial applications to meet the challenging requirements of emissions reduction. On the other hand, the complexity in the underlying mechanism of dislocation strengthening in this case may shed light on a different route of material strengthening by stimulating dislocation activities, rather than impeding motion of dislocations.

A linear model of ductile plastic damage

International Nuclear Information System (INIS)

Lemaitre, J.

1983-01-01

A three-dimensional model of isotropic ductile plastic damage based on a continuum damage variable on the effective stress concept and on thermodynamics is derived. As shown by experiments on several metals and alloys, the model, integrated in the case of proportional loading, is linear with respect to the accumulated plastic strain and shows a large influence of stress triaxiality [fr

Effect of void cluster on ductile failure evolution

DEFF Research Database (Denmark)

Tvergaard, Viggo

2016-01-01

The behavior of a non-uniform void distribution in a ductile material is investigated by using a cell model analysis to study a material with a periodic pattern of void clusters. The special clusters considered consist of a number of uniformly spaced voids located along a plane perpendicular...

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

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.

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.

Effects of structure and defect on fatigue limit in high strength ductile irons

International Nuclear Information System (INIS)

Kim, Jin Hak; Kim, Min Gun

2000-01-01

In this paper, the influence of several factors such as hardness, internal defect and non-propagating crack on fatigue limits was investigated with three kinds of ductile iron specimens. From the experimental results the fatigue limits were examined in relation with hardness and tensile strength in case of high strength specimens under austempering treatment; in consequence the marked improvement of fatigue limits were not showed. The maximum defect size was an important factor to predict and to evaluate the fatigue limits of ductile irons. And, the quantitative relationship between the fatigue limits(σ ω ) and the maximum defect size(√area max ) was expressed as σ ω n · √area max =C 2 . Also, it was possible to explain the difference for the fatigue limits in three ductile irons by introduction of the non-propagating crack rates

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

Influence of deformation conditions on texture formation and ductility in titanium alloys under hydrostatic pressure

International Nuclear Information System (INIS)

Dekun, A.M.; Kushakevich, S.A.; Adamesku, R.A.; Khmelinin, Yu.F.; Beresnev, B.I.; Shishmintsev, V.F.

1982-01-01

The influence of hot pressing parameters on microstructure, texture and mechanical properties of bars from titanium alloys VT1-0, VT5-1, (α-alloys) and VT3-1 (α+ν-alloy) has been investigated. Mechanical testing of samples has been performed under hydrostatic pressure from 200 to 800 MPa. It is shown that the temperature, deformation degree and type of the structure obtained exert a slight effect on mechanical properties of bars. The texture heterogeneity is more pronounced in α-alloys. It has been found that hydrostatic pressure during sample tensile testing improves their ductility characteristics

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

Science.gov (United States)

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

2018-04-01

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

Influence of cooling rate and antimony addition content on graphite morphology and mechanical properties of a ductile iron

Directory of Open Access Journals (Sweden)

Liu Zhe

2012-05-01

Full Text Available Cooling rate and inoculation practice can greatly affect the graphite morphology of ductile irons. In the present research, the effects of the cooling rate and antimony addition on the graphite morphology and mechanical properties of ductile irons have been studied. Three ductile iron castings were prepared through solidification under cooling conditions S (slow, M (medium and F (fast. The cooling rates around the equilibrium eutectic temperature (1,150 ℃ for these cooling conditions (S, M and F were set at 0.21 ℃·min-1, 0.32 ℃·min-1 and 0.37 ℃·min-1, respectively. In addition, four ductile iron castings were prepared by adding 0.01%, 0.02%, 0.03% and 0.04% (by weight antimony, respectively under the slow cooling condition. The results show that the nodularity index, tensile strength and hardness of the ductile iron castings without antimony addition are all improved with the increase of cooling rate, while the ductile iron casting solidified under the medium cooling rate possesses the largest number of graphite nodules. Furthermore, for the four antimony containing castings, the graphite morphology and tensile strength are also improved by the antimony additions, and the effect of antimony addition is intensified when the addition increases from 0.01% to 0.03%. Moreover, the rare earth elements (REE/antimony ratio of 2 appears to be the most effective for fine nodular graphite formation in ductile iron.

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.

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...

The Mechanism of High Ductility for Novel High-Carbon Quenching-Partitioning-Tempering Martensitic Steel

Science.gov (United States)

Qin, Shengwei; Liu, Yu; Hao, Qingguo; Wang, Ying; Chen, Nailu; Zuo, Xunwei; Rong, Yonghua

2015-09-01

In this article, a novel quenching-partitioning-tempering (Q-P-T) process was applied to treat Fe-0.6C-1.5Mn-1.5Si-0.6Cr-0.05Nb hot-rolled high-carbon steel and the microstructures including retained austenite fraction and the average dislocation densities in both martensite and retained austenite were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, respectively. The Q-P-T steel exhibits high strength (1950 MPa) and elongation (12.4 pct). Comparing with the steel treated by traditional quenching and tempering (Q&T) process, the mechanism of high ductility for high-carbon Q-P-T steel is revealed as follows. Much more retained austenite existing in Q-P-T steel than in Q&T one remarkably enhances the ductility by the following two effects: the dislocation absorption by retained austenite effect and the transformation-induced plasticity effect. Besides, lower dislocation density in martensite matrix produced by Q-P-T process plays an important role in the improvement of ductility. However, some thin plates of twin-type martensite embedded in dislocation-type martensite matrix in high-carbon Q-P-T steel affect the further improvement of ductility.

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

Surveillance test of OWL-2 inpile tube

International Nuclear Information System (INIS)

Shimizu, Masatsugu; Itoh, Noboru

1976-08-01

A series of irradiation surveillance tests performed in integrity evaluation of an inpile tube for the test loop OWL-2 are described. Specimens were exposed to the neutron fluences from 1 x 10 20 to 3.4 x 10 21 n/cm 2 (>1 MeV), and subjected to post-irradiation tensile test at room temperature and service temperature 285 0 C. The strength increased and the ductility decreased with increasing neutron fluence. The reduction in fracture ductility due to neutron irradiation in the fluence range was insignificant, and the elongation of 33% was retained even for the maximum neutron fluence at 285 0 C. Little decrease of the ductility with fluence indicates that the tube would be in service for long time, ie to the integral fluence of 3.4 x 10 21 n/cm 2 . (auth.)

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.)

A ductile fracture criterion with Zener-Hollomon parameter of pure molybdenum sheet in thermal forming

Directory of Open Access Journals (Sweden)

Wang Chu

2015-01-01

Full Text Available Formability of pure molybdenum in thermal forming process has been greatly improved, but it is still hard to avoid the generation of rupture and other quality defects. In this paper, a ductile fracture criterion of pure molybdenum sheet in thermal forming was established by considering the plastic deformation capacity of material and stress states, which can be used to describe fracture behaviour and critical rupture prediction of pure molybdenum sheet during hot forming process. Based on the isothermal uniaxial tensile tests which performed at 993 to 1143 K with strain rate range from 0.0005 to 0.2 s−1, the material parameters are calculated by the combination method of experiment with FEsimulation. Based on the observation, new fracture criteria can be expressed as a function of Zener-Hollomon parameter. The critical fracture value that calculated by Oyane-Sato criterion increases with increasing temperature and decreasing strain rate. The ductile fracture criterion with Zener-Hollomon parameter of pure molybdenum in thermal forming is proposed.

A Study On Critical Thinning In Thin-walled Tube Bending Of Al-Alloy 5052O Via Coupled Ductile Fracture Criteria

International Nuclear Information System (INIS)

Li Heng; Yang He; Zhan Mei

2010-01-01

Thin-walled tube bending(TWTB) method of Al-alloy tube has attracted wide applications in aerospace, aviation and automobile,etc. While, under in-plane double tensile stress states at the extrados of bending tube, the over-thinning induced ductile fracture is one dominant defect in Al-alloy tube bending. The main objective of this study is to predict the critical wall-thinning of Al-alloy tube bending by coupling two ductile fracture criteria(DFCs) into FE simulation. The DFCs include Continuum Damage Mechanics(CDM)-based model and GTN porous model. Through the uniaxial tensile test of the curved specimen, the basic material properties of the Al-alloy 5052O tube is obtained; via the inverse problem solution, the damage parameters of both the two fracture criteria are interatively determined. Thus the application study of the above DFCs in the TWTB is performed, and the more reasonable one is selected to obtain the critical thinning of Al-alloy tube in bending. The virtual damage initiation and evolution (when and where the ductile fracture occurs) in TWTB are investigated, and the fracture mechanisms of the voided Al-alloy tube in tube bending are consequently discussed.

Experimental analysis of flow of ductile cast iron in stream lined gating systems

DEFF Research Database (Denmark)

Skov-Hansen, Søren Peter; Tiedje, Niels Skat

2008-01-01

Streamlined gating systems have been developed for production of high integrity ductile cast iron parts. Flow of ductile cast iron in streamlined gating systems was studied in glass fronted sand moulds where flow in the gating system and casting was recorded by a digital video camera. These results...... show how the quality of pouring, design of ingates, design of bends and flow over cores influence melt flow and act to determine the quality of the castings....

Ductile failure of pipes with defects under combined pressure and bending

International Nuclear Information System (INIS)

Darlaston, B.J.L.; Harrison, R.P.

1977-01-01

The main part of the experimental programme was carried out on 3.5'' diam. pipes with a wall thickness of 0.064''. Various lengths of defect were assessed but only two depths, 0.044'' and 0.060''. Some full penetration defect tests were carried out under bending loading. The defects were 0.012'' wide and nominally flat bottomed. The tensile properties of the pipes were determined by taking specimens from each of the tubes. The pipes were exposed to pressure only test, bending only test and combined bending and pressure test. The results are given in tables. The observations led to the postulation of a design rule relating to the effect of defect in pipes under combined internal pressure and bending. It applies only to ductile situations in which the mode of failure is by a collapse mechanism: If the failure of a pipe containing an axial defect occurs by plastic collapse then provided the bending moment does not exceed half that for collapse due to bending alone, it will have a negligible effect on the failure pressure. (J.B.)

Tensile properties and bend ductility of (Fe,Ni)3V long-range-ordered alloys after irradiation in HFIR

International Nuclear Information System (INIS)

Braski, D.N.

1984-01-01

The objective of this work was to determine the effect of neutron irradiation on the tensile properties and bend ductility of (Fe,Ni) 3 V long-range-ordered (LRO) alloys. Several (Fe,Ni) 3 V LRO alloys were irradiated in HFIR-CTR-42 and -43 at 400 to 600 0 C, to approximately 10 dpa and approximately 1000 at. ppm He. Additions of cerium or carbon and the use of cold-worked microstructures did not improve the embrittlement resistance of the LRO alloys. The LRO-37-5RS alloy, with a microstructure produced by rapid solidification, exhibited the highest ductilities, and further study of the RS microstructure is warranted. The correlation between bend ductility and tensile ductility was poor

Ductile Damage and Fatigue Behavior of Semi-Finished Tailored Blanks for Sheet-Bulk Metal Forming Processes

Science.gov (United States)

Besserer, Hans-Bernward; Hildenbrand, Philipp; Gerstein, Gregory; Rodman, Dmytro; Nürnberger, Florian; Merklein, Marion; Maier, Hans Jürgen

2016-03-01

To produce parts from sheet metal with thickened functional elements, bulk forming operations can be employed. For this new process class, the term sheet-bulk metal forming has been established recently. Since sheet-bulk metal forming processes such as orbital forming generates triaxial stress and strain states, ductile damage is induced in the form of voids in the microstructure. Typical parts will experience cyclic loads during service, and thus, the influence of ductile damage on the fatigue life of parts manufactured by orbital forming is of interest. Both the formation and growth of voids were characterized following this forming process and then compared to the as-received condition of the ferritic deep drawing steel DC04 chosen for this study. Subsequent to the forming operation, the specimens were fatigued and the evolution of ductile damage and the rearrangement of the dislocation networks occurring during cyclic loading were determined. It was shown, that despite an increased ductile damage due to the forming process, the induced strain hardening has a positive effect on the fatigue life of the material. However, by analyzing the fatigued specimens a development of the ductile damage by an increasing number of voids and a change in the void shape were detected.

Austempered ductile iron (ADI) for railroad wheels : final report.

Science.gov (United States)

2017-01-31

The purpose of this project is to investigate the potential for austempered ductile iron (ADI) to be used as an alternative material for the production of rail wheels, which are currently cast or forged steel which is commonly heat treated. ADI has s...

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.))

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)

Prediction of forming limit in hydro-mechanical deep drawing of steel sheets using ductile fracture criterion

Science.gov (United States)

Oh, S.-T.; Chang, H.-J.; Oh, K. H.; Han, H. N.

2006-04-01

It has been observed that the forming limit curve at fracture (FLCF) of steel sheets, with a relatively higher ductility limit have linear shapes, similar to those of a bulk forming process. In contrast, the FLCF of sheets with a relatively lower ductility limit have rather complex shapes approaching the forming limit curve at neck (FLCN) towards the equi-biaxial strain paths. In this study, the FLCFs of steel sheets were measured and compared with the fracture strains predicted from specific ductile fracture criteria, including a criterion suggested by the authors, which can accurately describe FLCFs with both linear and complex shapes. To predict the forming limit for hydro-mechanical deep drawing of steel sheets, the ductile fracture criteria were integrated into a finite element simulation. The simulation, results based on the criterion suggested by authors accurately predicted the experimetal, fracture limits of steel sheets for the hydro-mechanical deep drawing process.

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.

Ductile crack initiation and propagation assessed via in situ synchrotron radiation-computed laminography

International Nuclear Information System (INIS)

Morgeneyer, T.F.; Helfen, L.; Sinclair, I.; Proudhon, H.; Xu, F.; Baumbach, T.

2011-01-01

Ductile crack initiation and propagation within a naturally aged aluminium alloy sheet has been observed in situ via synchrotron radiation-computed laminography, a technique specifically adapted to three-dimensional imaging of thin objects that are laterally extended. Voids and intermetallic particles, and their subsequent evolution during ductile crack extension at different associated levels of stress triaxiality, were clearly observed within fracture coupons of a reasonable engineering length-scale, overcoming the conventional sample size limitation of computed tomography at high resolutions.

A new ductile moment-resisting connection for precast concrete frames in seismic regions: An experimental investigation

OpenAIRE

Parastesh, H.; Hajirasouliha, I.; Ramezani, R.

2014-01-01

A new ductile moment-resisting beam–column connection is developed for precast reinforced concrete (RC) frames in high seismic zones. The proposed connection provides good structural integrity in the connections and can reduce construction time by eliminating the need for formworks and welding, and minimizing cast-in-place concrete volume. A series of cyclic loading tests were carried out on six full-scale interior and exterior precast connections and two monolithic connections, all designed ...

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

Evolution of dislocations and twins in a strong and ductile nanotwinned steel

International Nuclear Information System (INIS)

Zhou, P.; Liang, Z.Y.; Liu, R.D.; Huang, M.X.

2016-01-01

A twinning-induced plasticity (TWIP) steel was subjected to a simple processing route (i.e. cold rolling followed by a recovery heat treatment) suitable for large-scale industrial production, resulting in the production of a strong and ductile nanotwinned steel. This nanotwinned steel combines high yield strength (1450 MPa), high ultimate tensile strength (1600 MPa) and good ductility (25% total elongation). Detailed transmission electron microscopy observation reveals that the twin volume fraction of the nanotwinned steel remains constant during tensile deformation. This is different to the deformation behaviour of recrystallized TWIP steels whose twin volume fraction increase continuously with strain during tensile deformation. The constant twin volume fraction indicates that a maximum twin volume fraction has been reached during the cold rolling process. In contrast, the dislocation density of the nanotwinned steel increases with strain as measured by the synchrotron X-ray diffraction experiments. In other words, the plastic deformation of the nanotwinned steel is mainly accommodated by glide and multiplication of dislocations. Based on the experimental results, an analytical model was developed to capture the respective effects of dislocations and twins on the strength and ductility of the present nanotwinned steel. The modelling results indicate that the strength is contributed by both twins and dislocations while the ductility is mainly attributed to dislocation multiplication. -- Graphical abstract: (a) TEM bright field image showing intensive nanotwins in the nanotwinned steel. Selected area diffraction pattern obtained within the red circle. (b) The engineering stress–stain curve of the nanotwinned steel. Display Omitted

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.

Observations on Mode I ductile tearing in sheet metals

DEFF Research Database (Denmark)

El-Naaman, Salim Abdallah; Nielsen, Kim Lau

2013-01-01

Cracked ductile sheet metals, subject to Mode I tearing, have been observed to display a variety of fracture surface morphologies depending on the material properties, and a range of studies on the fracture surface appearance have been published in the literature. Whereas classical fractures...

Effect of prestrain on ductility and toughness in high strength line pipe steels

Energy Technology Data Exchange (ETDEWEB)

Shinohara, Y.; Besson, J. [Paristech, Evry (France). Centre des Materiaux, Mines Paris; Madi, Y. [Ecole d' Ingenieurs, Sceaux (France). Ermess EPF; Paristech, Evry (France). Centre des Materiaux, Mines Paris

2009-07-01

The anisotropic plasticity, ductility and toughness of an X100 steel pipeline was investigated both before and after a series of prestraining experiments. The aim of the study was to determine the effect of prestraining on ductility and toughness in high strength pipe steels. Results of the study showed that primary void growth and coalescence was dependent on initial plastic anisotropy and not dependent on tensile prestrain. Secondary void nucleation and growth was not influenced by either the initial plastic anisotropy or by prestraining. Scanning electron microscopy (SEM) studies showed that the main damage mechanism was the void growth of primary dimples. Dimples in the prestrained materials were larger than those observed in materials that had not been prestrained. However, the effect on prestrain on dimple size was limited. Results showed both plastic and rupture anisotropies. It was concluded that prestraining induces a decrease in ductility, but has a significant impact on toughness. 4 refs., 2 tabs., 12 figs.

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 ...

Effect of initial void shape on ductile failure in a shear field

DEFF Research Database (Denmark)

Tvergaard, Viggo

2015-01-01

For voids in a shear field unit cell model analyses have been used to show that ductile failure is predicted even though the stress triaxiality is low or perhaps negative, so that the void volume fraction does not grow during deformation. Here, the effect of the void shape is studied by analyzing...... with circular cross-section, i.e. the voids in shear flatten out to micro-cracks, which rotate and elongate until interaction with neighboring micro-cracks gives coalescence. Even though the mechanism of ductile failure is the same, the load carrying capacity predicted, for the same initial void volume fraction...

Fracture and fatigue considerations in the development of ductile-phase reinforced intermetallic-matrix composites

International Nuclear Information System (INIS)

Venkateswara Rao, K.T.; Ritchie, R.O.

1994-01-01

The salient microstructural factors influencing fracture and fatigue-crack growth resistance of ductile-particle reinforced intermetallic-matrix composites at ambient temperature are reviewed through examples from the Nb/MoSi 2 , TiNb/TiAl, Nb/TiAl and Nb/Nb 3 Al systems; specific emphasis is placed on properties and morphology of the reinforcement and its interfacial properties with the matrix. It is shown that composites must be fabricated with a high aspect ratio ductile-reinforcement morphology in order to promote crack-particle interception and resultant crack bridging for improved fracture and fatigue properties. Concurrently, however, the ductile phases have contrasting effects on crack growth under monotonic vs. cyclic loading suggesting that composite microstructures tailored for optimal toughness may not necessarily yield optimal fatigue resistance. Perspectives for the future development of damage-tolerant intermetallic-composite microstructures are discussed

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.

Hot drawn Fe–6.5 wt.%Si wires with good ductility

International Nuclear Information System (INIS)

Yang, W.; Li, H.; Yang, K.; Liang, Y.F.; Yang, J.; Ye, F.

2014-01-01

Highlights: • Fe–6.5wt%Si steel wire with diameter of 1.6 mm can be successfully obtained by hot drawing process. • The ductility of Fe–6.5wt%Si alloy can be improved significantly when it is fabricated in the form of wire. • The Dc magnetic property of Fe–6.5wt%Si steel wire 1.6 mm in diameter is excellent, which is close to that of 0.3 mm thick cold-rolling sheet. - Abstract: Fe–6.5 wt.%Si high silicon steel wires with a diameter of 1.6 mm are fabricated successfully by hot drawing. The high silicon steel wires show much better ductility than sheets. The tensile strength and elongation of the wires at the room temperature can reach 1.31 GPa and 1.4%, respectively. The tensile strength and elongation of the rolling sheet at the room temperature are 0.8 GPa and 0, respectively. The microstructure analyses show that the elongated grains after drawing and reduced ordering phases by deformation in the wires might contribute to its good ductility. Bs value of 1.437 T and Hc value of 16.96 A/m are obtained for the wire after proper heat treatment for the wires

Brittle and ductile friction modeling of triggered tremor in Guerrero, Mexico

Science.gov (United States)

Zhang, Y.; Daub, E. G.; Wu, C.

2017-12-01

Low frequency earthquakes (LFEs), which make up the highest amplitude portions of non-volcanic tremor, are mostly found along subduction zones at a depth of 30-40km which is typically within the brittle-ductile transition zone. Previous studies in Guerrero, Mexico demonstrated a relationship between the bursts of LFEs and the contact states of fault interfaces, and LFEs that triggered by different mechanisms were observed along different parts of the subduction zone. To better understand the physics of fault interfaces at depth, especially the influence of contact states of these asperities, we use a brittle-ductile friction model to simulate the occurrence of LFE families from a model of frictional failure and slip. This model takes the stress state, slip rate, perturbation force, fault area, and brittle-ductile frictional contact characteristics and simulates the times and amplitudes of LFE occurrence for a single family. We examine both spontaneous and triggered tremor occurrence by including stresses due to external seismic waves, such as the 2010 Maule Earthquake, which triggered tremor and slow slip on the Guerrero section of the subduction zone. By comparing our model output with detailed observations of LFE occurrence, we can determine valuable constraints on the frictional properties of subduction zones at depth.

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

Indian Academy of Sciences (India)

Unknown

The strain hardening capacity has a marked effect on void size, and is an indicator of fracture .... a model of ductile failure based on the concept that the critical step in the .... Ashby M F, Gandhi C and Taplin D M R 1979 Acta Metal. 27. 699.

Effect of Boron on the Hot Ductility of Resulfurized Low-Carbon Free-Cutting Steel

Science.gov (United States)

Liu, Hai-tao; Chen, Wei-qing

2015-09-01

The hot ductility of resulfurized low-carbon free-cutting steel with boron additives is studied in the temperature range 850 - 1200°C with the help of a Gleeble-1500 thermomechanical simulator. The introduction of boron increases hot ductility, especially at 900 - 1050°C. In the single-phase austenitic region, this effect is caused by segregation of boron over grain boundaries, acceleration of dynamic recrystallization, and solid-solution softening of deformed austenite.

Effects of Non-metallic Inclusions on Hot Ductility of High Manganese TWIP Steels Containing Different Aluminum Contents

Science.gov (United States)

Wang, Yu-Nan; Yang, Jian; Wang, Rui-Zhi; Xin, Xiu-Ling; Xu, Long-Yun

2016-06-01

The characteristics of inclusions in Fe-16Mn- xAl-0.6C ( x = 0.002, 0.033, 0.54, 2.10 mass pct) steels have been investigated and their effects on hot ductility of the high manganese TWIP steels have been discussed. Ductility is very poor in the steel containing 0.54 mass pct aluminum, which is lower than 20 pct in the temperature range of 873 K to 1473 K (600 °C to 1200 °C). For the steels containing 0.002 and 2.10 mass pct aluminum, ductility is higher than 40 pct in the same temperature range. The hot ductility of steel containing 0.033 mass pct aluminum is higher than 30 pct throughout the temperature range under examination. With increasing aluminum content, the main inclusions in the steels change along the route of MnO/(MnO + MnS) → MnS/(Al2O3 + MnS) → AlN/(Al2O3 + MnS)/(MgAl2O4 + MnS) → AlN. The thermodynamic results of inclusion types calculated with FactSage software are in agreement with the experimental observation results. The inclusions in the steels containing 0.002 mass pct aluminum do not deteriorate the hot ductility. MnS inclusions whose average size, number density, and volume ratio are 1.12 μm, 15.62 mm-2, and 2.51 × 10-6 in the steel containing 0.033 mass pct aluminum reduce the ductility. In the steel containing 0.54 mass pct aluminum, AlN inclusions whose average size, number density, and volume ratio are 0.878 μm, 16.28 mm-2 and 2.82 × 10-6 can precipitate at the austenite grain boundaries, prevent dynamic recrystallization and deteriorate the hot ductility. On the contrary, in the steel containing 2.10 mass pct aluminum, the average size, number density and volume ratio of AlN inclusions change to 2.418 μm, 35.95 mm-2, and 2.55 × 10-5. They precipitate in the matrix, which do not inhibit dynamic recrystallization and thereby do not lead to poor hot ductility.

The elasto plastic fracture mechanics in ductile metal sheets

International Nuclear Information System (INIS)

Khan, M.A.; Malik, M.N.; Naeem, A.; Haq, A.U.; Atkins, A.G.

1999-01-01

The crack initiation of propagation in ductile metal sheets are caused by various micro and macro changes taking place due to material properties, applied loads, shape of the indenter (tool geometry) and the environmental conditions. These microstructural failures are directly related to the atomic bonding, crystal lattices, grain boundary status, material flaws in matrix, inhomogeneities and anisotropy in the metal sheets. The Elasto-Plastic related energy based equations are applied to these Rigid Plastic materials to determine the onset of fracture in metal forming. The combined stress and strain criterion of a critical plastic work per unit volume is no more considered as a universal ductile fracture criterion, rather a critical plastic work per unit volume dependence on all sort of stresses (hydrostatic) are the required features for the sheet metal failure (fracture). In this present study, crack initiation and propagation are related empirically with fracture toughness and the application of the theory in industry to save energy. (author)

A proposal for an unusually stiff and moderately ductile hard coating material: Mo2BC

International Nuclear Information System (INIS)

Emmerlich, J; Music, D; Braun, M; Fayek, P; Schneider, J M; Munnik, F

2009-01-01

The elastic properties of Mo 2 BC were studied using ab initio calculations. The calculated bulk modulus of 324 GPa is 45% larger than that of Ti 0.25 Al 0.75 N and 14% smaller than that of c-BN, indicating a highly stiff material. The bulk modulus (B) to shear modulus (G) ratio is 1.72 at the transition from brittle to ductile behaviour. This, in combination with a positive Cauchy pressure (c 12 - c 44 ), suggests moderate ductility. When compared with a typical hard protective coating such as Ti 0.25 Al 0.75 N (B = 178 GPa; B/G = 1.44; negative Cauchy pressure), Mo 2 BC displays considerable potential as protective coating for metal cutting applications. In order to test this proposal, Mo 2 BC thin films were synthesized using dc magnetron sputtering from three plasma sources on Al 2 O 3 (0 0 0 1) at a substrate temperature of ∼900 0 C. The calculated lattice parameters are in good agreement with values determined from x-ray diffraction. The measured Young's modulus values of ∼460 ± 21 GPa are in excellent agreement with the 470 GPa value obtained by calculations. Scanning probe microscopy imaging of the residual indent revealed no evidence for crack formation as well as significant pile-up, which is consistent with the moderate plasticity predicted. The apparent contradiction between moderate ductility on the one hand and indentation hardness values of 29 GPa can be understood by considering the electronic structure particularly the extreme anisotropy. The presence of stiff Mo-C and Mo-B layers with metallic interlayer bonding enables this intriguing and unexpected property combination.

ASME codification of ductile cast iron cask for transport and storage of spent nuclear fuel

International Nuclear Information System (INIS)

Saegusa, Toshiari; Arai, Taku

2012-01-01

The CRIEPI has been executing research and development on ductile cast iron cask for transport and storage of spent nuclear fuel in order to diversify options of the casks. Based on the research results, the CRIEPI proposed materials standards (Section II) and structural design standards (Section III) for the ductile cast iron cask to the authoritative and international ASME (American Society of Mechanical Engineers) Codes. For the Section II, the CRIEPI proposed the JIS G 5504 material with additional requirement prohibiting repair of cast body by welding, etc. as well as the ASTM A874 material to the Part A. In addition, the CRIEPI proposed design stress allowables, physical properties (thermal conductivity, modulus of elasticity, etc.), and external pressure chart to the Part D. For the Section III, the CRIEPI proposed a fracture toughness requirement of the ductile cast iron cask at -40degC to WB and WC of Division 3. Additionally, the CRIEPI proposed a design fatigue curve of the ductile cast iron cask to Appendix of Division 1. This report describes the outline of the proposed standards, their bases, and the deliberation process in order to promote proper usage of the code, future improvement, etc. (author)

Numerical simulation of ductile-brittle behaviour of cracks in aluminium and bcc iron

International Nuclear Information System (INIS)

Zacharopoulos, Marios

2017-01-01

The principal aim of the present dissertation is to investigate the role of sharp cracks on the mechanical behaviour of crystals under load at the atomic scale. The question of interest is how a pure crystal, which contains a single crack in mechanical equilibrium, deforms. Two metals were considered: aluminium, ductile at any temperature below its melting point, and iron, being transformed from ductile to brittle upon decreasing temperature below T=77 K. Cohesive forces in both metals were modeled via phenomenological n-body potentials. A (010)[001] mode I nano-crack was introduced in the perfect crystalline lattice of each of the studied metals by using appropriate displacements ascribed by anisotropic elasticity. At T=0 K, equilibrium crack configurations were obtained via energy minimization with a mixed type of boundary conditions. Both models revealed that the crack configurations remained stable under a finite range of applied stresses due to the lattice trapping effect. The present thesis proposes a novel approach to interpret the intrinsic mechanical behaviour of the two metallic systems under loading. In particular, the ductile or brittle response of a crystalline system can be determined by examining whether the lattice trapping barrier of a pre-existing crack is sufficient to cause the glide of pre-existing static dislocations on the available slip systems. Simulation results along with experimental data demonstrate that, according to the model proposed, aluminium and iron are ductile and brittle at T=0 K, respectively. (author) [fr

Grain growth behavior and high-temperature high-strain-rate tensile ductility of iridium alloy DOP-26

International Nuclear Information System (INIS)

McKamey, C.G.; Gubbi, A.N.; Lin, Y.; Cohron, J.W.; Lee, E.H.; George, E.P.

1998-04-01

This report summarizes results of studies conducted to date under the Iridium Alloy Characterization and Development subtask of the Radioisotope Power System Materials Production and Technology Program to characterize the properties of the new-process iridium-based DOP-26 alloy used for the Cassini space mission. This alloy was developed at Oak Ridge National Laboratory (ORNL) in the early 1980's and is currently used by NASA for cladding and post-impact containment of the radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for interplanetary spacecraft. Included within this report are data generated on grain growth in vacuum or low-pressure oxygen environments; a comparison of grain growth in vacuum of the clad vent set cup material with sheet material; effect of grain size, test temperature, and oxygen exposure on high-temperature high-strain-rate tensile ductility; and grain growth in vacuum and high-temperature high-strain-rate tensile ductility of welded DOP-26. The data for the new-process material is compared to available old-process data

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.

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.

Ductile transition in nylon-rubber blends: influence of water

NARCIS (Netherlands)

Gaymans, R.J.; Borggreve, R.J.M.; Spoelstra, A.B.

1989-01-01

On nylon 6 and nylon 6/EPDM blends the influence of water on the glass transition temperature, mechanical properties, and the ductile transition temperature was studied. Blends of 10% and 20% were prepared with a particle size of 0.3 µm and the tensile properties, flexural moduli, torsion moduli,

Sliding wear and corrosion behaviour of alloyed austempered ductile iron subjected to novel two step austempering treatment

Science.gov (United States)

Sethuram, D.; Srisailam, Shravani; Rao Ponangi, Babu

2018-04-01

Austempered Ductile Iron(ADI) is an exciting alloy of iron which offers the design engineers the best combination high strength-to-weight ratio, low cost design flexibility, good toughness, wear resistance along with fatigue strength. The two step austempering procedure helps in simultaneously improving the tensile strength as-well as the ductility to more than that of the conventional austempering process. Extensive literature survey reveals that it’s mechanical and wear behaviour are dependent on heat treatment and alloy additions. Current work focuses on characterizing the two-step ADI samples (TSADI) developed by novel heat treatment process for resistance to corrosion and wear. The samples of Ductile Iron were austempered by the two-Step Austempering process at temperatures 300°C to 450°C in the steps of 50°C.Temperaturesare gradually increased at the rate of 14°C/Hour. In acidic medium (H2SO4), the austempered samples showed better corrosive resistance compared to conventional ductile iron. It has been observed from the wear studies that TSADI sample at 350°C is showing better wear resistance compared to ductile iron. The results are discussed in terms of fractographs, process variables and microstructural features of TSADI samples.

Effect of shrinkage porosity on mechanical properties of ferritic ductile iron

Directory of Open Access Journals (Sweden)

Wang Zehua

2013-05-01

Full Text Available Casting defects could largely affect the mechanical properties of casting products. A number of test pieces made of ductile iron (EN-GJS-400-18-LT with different levels of shrinkage porosity were prepared and then tensile and fatigue tests were performed to investigate the impact of shrinkage porosity on their mechanical properties. The results showed that the tensile strength decreases linearly with increasing of the shrinkage porosity. The tensile elongation decreases sharply with the increase of the shrinkage porosity mainly due to the non-uniform plastic deformation. The fatigue life also dramatically declines with increasing of the porosity and follows a power law relationship with the area percentage of porosity. The existence of the shrinkage porosity made the fatigue fracture complex. The shrinkage pores, especially those close to the surface usually became the crack initiation sites. For test pieces with less porosity, the fatigue fracture was clearly composed of crack initiation, propagation, and overloading. While for samples with high level of porosity, multiple crack initiation sites were observed.

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

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.

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

International Nuclear Information System (INIS)

Mejía, I.; Salas-Reyes, A.E.; Calvo, J.; Cabrera, J.M.

2015-01-01

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"−"3 s"−"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_2_3(B,C)_6 and B_4C 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.

DUCTILE URANIUM FUEL FOR NUCLEAR REACTORS AND METHOD OF MAKING

Science.gov (United States)

Zegler, S.T.

1963-11-01

The fabrication process for a ductile nuclear fuel alloy consisting of uranium, fissium, and from 0.25 to 1.0 wt% of silicon or aluminum or from 0.25 to 2 wt% of titanium or yttrium is presented. (AEC)

Numerical modelling of thin-walled hypereutectic ductile cast iron parts

DEFF Research Database (Denmark)

Pedersen, Karl Martin; Hattel, Jesper Henri; Tiedje, Niels Skat

2006-01-01

Solidification of hypereutectic thin-walled ductile cast iron has been modelled in one dimension taking into account the precipitation of off-eutectic austenite dendrites during solidification. The simulations have been compared with casting experiments on plate geometries with plate thicknesses...

Fuel powder production from ductile uranium alloys

International Nuclear Information System (INIS)

Clark, C.R.; Meyer, M.K.

1998-01-01

Metallic uranium alloys are candidate materials for use as the fuel phase in very-high-density LEU dispersion fuels. These ductile alloys cannot be converted to powder form by the processes routinely used for oxides or intermetallics. Three methods of powder production from uranium alloys have been investigated within the US-RERTR program. These processes are grinding, cryogenic milling, and hydride-dehydride. In addition, a gas atomization process was investigated using gold as a surrogate for uranium. (author)

Forming limit diagram of aluminum AA6063 tubes at high temperatures by bulge tests

International Nuclear Information System (INIS)

Hashemi, Seyed Jalal; Naeini, Hassan Moslemi; Liaghat, Gholamhossein; Tafti, Rooholla Azizi; Rahmani, Farzad

2014-01-01

A free bulge test and ductile fracture criteria were used to obtain the forming limit diagrams (FLD) of aluminum alloy AA6063 tubes at high temperatures. Ductile fracture criteria were calibrated using the results of uniaxial tension tests at various elevated temperatures and different strain rates through adjusting the Zener-Holloman parameter. High temperature free bulge test of tubes was simulated in finite element software Abaqus, and tube bursting was predicted using ductile fracture criteria under different loading paths. FLDs which were obtained from finite element simulation were compared to experimental results to select the most accurate criterion for prediction of forming limit diagram. According to the results, all studied ductile fracture criteria predict similarly when forming condition is close to the uniaxial tension, while Ayada criterion predicts the FLD at 473 K and 573 K very well.

Forming limit diagram of aluminum AA6063 tubes at high temperatures by bulge tests

Energy Technology Data Exchange (ETDEWEB)

Hashemi, Seyed Jalal; Naeini, Hassan Moslemi; Liaghat, Gholamhossein [Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Tafti, Rooholla Azizi [Yazd University, Yazd (Iran, Islamic Republic of); Rahmani, Farzad [Kar Higher Education Institute, Qazvin (Iran, Islamic Republic of)

2014-11-15

A free bulge test and ductile fracture criteria were used to obtain the forming limit diagrams (FLD) of aluminum alloy AA6063 tubes at high temperatures. Ductile fracture criteria were calibrated using the results of uniaxial tension tests at various elevated temperatures and different strain rates through adjusting the Zener-Holloman parameter. High temperature free bulge test of tubes was simulated in finite element software Abaqus, and tube bursting was predicted using ductile fracture criteria under different loading paths. FLDs which were obtained from finite element simulation were compared to experimental results to select the most accurate criterion for prediction of forming limit diagram. According to the results, all studied ductile fracture criteria predict similarly when forming condition is close to the uniaxial tension, while Ayada criterion predicts the FLD at 473 K and 573 K very well.

In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

Science.gov (United States)

Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

2004-03-23

A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

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

Novel compaction resistant and ductile nanocomposite nanofibrous microfiltration membranes.

Science.gov (United States)

Homaeigohar, Seyed Shahin; Elbahri, Mady

2012-04-15

Despite promising filtration abilities, low mechanical properties of extraordinary porous electrospun nanofibrous membranes could be a major challenge in their industrial development. In addition, such kind of membranes are usually hydrophobic and non-wettable. To reinforce an electrospun nanofibrous membrane made of polyethersulfone (PES) mechanically and chemically (to improve wettability), zirconia nanoparticles as a novel nanofiller in membrane technology were added to the nanofibers. The compressive and tensile results obtained through nanoindentation and tensile tests, respectively, implied an optimum mechanical properties after incorporation of zirconia nanoparticles. Especially compaction resistance of the electrospun nanofibrous membranes improved significantly as long as no agglomeration of the nanoparticles occurred and the electrospun nanocomposite membranes showed a higher tensile properties without any brittleness i.e. a high ductility. Noteworthy, for the first time the compaction level was quantified through a nanoindentation test. In addition to obtaining a desired mechanical performance, the hydrophobicity declined. Combination of promising properties of optimum mechanical and surface chemical properties led to a considerably high water permeability also retention efficiency of the nanocomposite PES nanofibrous membranes. Such finding implies a longer life span and lower energy consumption for a water filtration process. Copyright © 2012 Elsevier Inc. All rights reserved.

Ductile-phase toughening in V-V3Si in situ composites

International Nuclear Information System (INIS)

Henshall, G.; Strum, M.J.; Bewlay, B.P.; Sutliff, J.A.

1997-01-01

This article describes the room-temperature fracture behavior of ductile-phase-toughened V-V 3 Si in situ composites that were produced by arc melting (AM), cold-crucible induction melting (IM), and cold-crucible directional solidification (DS). Composites were produced containing a wide range of microstructures, interstitial impurity contents, and volume fractions of the ductile V-Si solid solution phase, denoted (V). The fracture toughness of these composites generally increases as the volume fraction of (V) increases, but is strongly influenced by the microstructure, the mechanical properties of the component phases, and the crystallographic orientation of the (V) phase with respect to the maximum principal stress direction. For eutectic composites that have a (V) volume fraction of about 50 pct, the fracture toughness increases with decreasing ''''effective'''' interstitial impurity concentration, [I] = [N] + 1.33 [O] + 9 [H]. As [I] decreases from 1,400 ppm (AM) to 400 ppm (IM), the fracture toughness of the eutectic composites increases from 10 to 20 MPa √m. Further, the fracture toughness of the DS eutectic composites is greater when the crack propagation direction is perpendicular, rather than parallel, to the composite growth direction. These results are discussed in light of conventional ductile-phase bridging theories, which alone cannot fully explain the fracture toughness of V-Si in situ composites

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%

Plastic Strain Induced Damage Evolution and Martensitic Transformation in Ductile Materials at Cryogenic Temperatures

CERN Document Server

Garion, C

2002-01-01

The Fe-Cr-Ni stainless steels are well known for their ductile behaviour at cryogenic temperatures. This implies development and evolution of plastic strain fields in the stainless steel components subjected to thermo-mechanical loads at low temperatures. The evolution of plastic strain fields is usually associated with two phenomena: ductile damage and strain induced martensitic transformation. Ductile damage is described by the kinetic law of damage evolution. Here, the assumption of isotropic distribution of damage (microcracks and microvoids) in the Representative Volume Element (RVE) is made. Formation of the plastic strain induced martensite (irreversible process) leads to the presence of quasi-rigid inclusions of martensite in the austenitic matrix. The amount of martensite platelets in the RVE depends on the intensity of the plastic strain fields and on the temperature. The evolution of the volume fraction of martensite is governed by a kinetic law based on the accumulated plastic strain. Both of thes...

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)

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

The effect of austenitizing conditions in the ductile iron hardening process on longitudinal ultrasonic wave velocity

Directory of Open Access Journals (Sweden)

A. W. Orłowicz

2014-04-01

Full Text Available The paper presents results of a research on the effect of austenitizing temperature and time adopted in the hardening operation on the ultrasonic wave velocity in ductile iron. It has been found that with increasing austenitizing temperature and with the passage of the austenitizing time, a monotonic decrease of the ultrasonic longitudinal wave velocity value occurred. Implementation of ultrasonic testing of results obtained in the course of the cast iron hardening process both in production and as-cast conditions, requires development of a test methodology that must take into account the influence of base material structure (degree of nodularization, graphite precipitation count on the ultrasound wave velocity.

Ultrasonic testing of pre-turned contours for large components made of ductile iron; Ultraschallpruefung an Vordrehkonturen fuer grosse Bauteile aus Gusseisen mit Kugelgraphit

Energy Technology Data Exchange (ETDEWEB)

Schmitte, Till; Chichkov, Nikolai; Nemitz, Oliver; Orth, Thomas [Salzgitter Mannesmann Forschung GmbH, Duisburg (Germany); Hocks, Heinrich Jr.; Rusche, Sascha; Opalla, Dirk; Frank, Joerg [GNS Gesellschaft fuer Nuklear-Service mbH, Essen (Germany)

2015-07-01

In the ultrasonic testing of large, thick-walled components made of ductile iron partial acoustic paths of several meters are needed. Considered here are cylindrical components such as the body of CASTOR containers with diameters 2-3 m, a height of up to 6 m and a wall thickness of 500 mm. So far, an automated technique for this is not available, therefore such components are checked in a complex and lengthy process by manual ultrasonic testing. The development and design of the testing by means of simulations and the realization as a mobile testing device are topics of this paper. Measurements on a reference body with test reflectors in different depths are presented and discussed. [German] Bei der Ultraschall-Pruefung von grossen, dickwandigen Bauteilen aus Gusseisen mit Kugelgraphit werden teilweise Schallwege von mehreren Metern noetig. Betrachtet werden hier zylinderfoermige Bauteile, wie die Koerper von CASTOR-Behaeltern, mit Durchmessern zwischen 2 und 3 m, einer Hoehe von bis zu 6 m und Wanddicken von ca. 500 mm. Bisher ist eine automatisierte Technik hierfuer nicht verfuegbar, daher werden derartige Bauteile in einem aufwaendigen und langwierigen Prozess mittels manueller Schallung geprueft. Zur Erhoehung der Nachweissicherheit und zur Steigerung der Effizienz im Pruefablauf sollen nun senkrecht zur Achse des zylinderfoermigen Bauteils liegende unzulaessige Anzeigen im gesamten Mantelvolumen durch eine teilautomatisierte Pruefung ausgeschlossen werden. Die Entwicklung und Auslegung der Prueftechnik mittels Simulationen und die Realisierung als mobile Pruefvorrichtung sind Themen dieses Beitrags. Messungen an einem Referenzkoerper mit Testreflektoren in verschiedenen Tiefen werden vorgestellt und diskutiert.

Simulation of seismic waves in the brittle-ductile transition (BDT) using a Burgers model

Science.gov (United States)

Poletto, Flavio; Farina, Biancamaria; Carcione, José Maria

2014-05-01

The seismic characterization of the brittle-ductile transition (BDT) in the Earth's crust is of great importance for the study of high-enthalpy geothermal fields in the proximity of magmatic zones. It is well known that the BDT can be viewed as the transition between zones with viscoelastic and plastic behavior, i.e., the transition between the upper, cooler, brittle crustal zone, and the deeper ductile zone. Depending on stress and temperature conditions, the BDT behavior is basically determined by the viscosity of the crustal rocks, which acts as a key factor. In situ shear stress and temperature are related to shear viscosity and steady-state creep flow through the Arrhenius equation, and deviatory stress by octahedral stress criterion. We present a numerical approach to simulate the propagation of P-S and SH seismic waves in a 2D model of the heterogeneous Earth's crust. The full-waveform simulation code is based on a Burgers mechanical model (Carcione, 2007), which enables us to describe both the seismic attenuation effects and the steady-state creep flow (Carcione and Poletto, 2013; Carcione et al. 2013). The differential equations of motion are calculated for the Burgers model, and recast in the velocity-stress formulation. Equations are solved in the time domain using memory variables. The approach uses a direct method based on the Runge-Kutta technique, and the Fourier pseudo-spectral methods, for time integration and for spatial derivation, respectively. In this simulation we assume isotropic models. To test the code, the signals generated by the full-waveform simulation algorithm are compared with success to analytic solutions obtained with different shear viscosities. Moreover, synthetic results are calculated to simulate surface and VSP seismograms in a realistic rheological model with a dramatic temperature change, to study the observability of BDT by seismic reflection methods. The medium corresponds to a selected rheology of the Iceland scenario

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.

Evaluation of Floor Response Spectrum considering Ductility of Structure

International Nuclear Information System (INIS)

Park, Junhee; Choi, In-Kil

2014-01-01

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 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

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

Abstract. Design of primary heat transport (PHT) piping of pressurised heavy water reactors (PHWR) has to ensure implementation of leak-before-break con- cepts. In order to be able to do so, the ductile fracture characteristics of PHT piping material have to be quantified. In this paper, the fracture resistance of SA333, Grade.

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

Fractographic observations of cleavage initiation in the ductile-brittle transition region of a reactor-pressure-vessel steel

International Nuclear Information System (INIS)

Rosenfield, A.R.; Shetty, D.K.; Skidmore, A.J.

1983-01-01

This note reports the results of a fractographic study conducted on a group of 1T compact fracture toughness specimens of a heavy-section A508 steel denoted TSE6 tested in the ductile-brittle transition region (22 and 82 0 C). The fatigue-precracked specimens were loaded at a rapid rate (760 or 550 mm per second) to promote cleavage-crack growth and lower-bound toughness behavior. All specimens experienced unstable cleavage fracture prior to reaching a maximum in the load displacement curve. Some ductile crack growth occurred in half of the specimens. The objective of fractographic examinations was to understand the observed statistical variations in cleavage initiation by (a) locating the origins of unstable cleavage fracture in the vicinity of the fatigue-precrack or ductilerupture crack fronts, (b) identifying microstructural features associated with the triggering of cleavage, and (c) documenting characteristic fracture surface dimensions such as the extent of stable-crack growth prior to unstable cleavage (Δα) and the distance of the cleavage origin from the ductilerupture front, /chi/ (or fatigue-crack front when Δα = 0)

Effect of nickel plating upon tensile tests of uranium--0.75 titanium alloy

International Nuclear Information System (INIS)

Hemperly, V.C.

1975-01-01

Electrolytic-nickel-plated specimens of uranium-0.75 wt percent titanium alloy were tested in air at 20 and 100 percent relative humidities. Tensile-test ductility values were lowered by a high humidity and also by nickel plating alone. Baking the nickel-plated specimens did not eliminate the ductility degradation. Embrittlement because of nickel plating was also evident in tensile tests at -34 0 C. (U.S.)

Three-dimensional microstructural effects on plane strain ductile crack growth

DEFF Research Database (Denmark)

Tvergaard, Viggo; Needleman, Alan

2006-01-01

Ductile crack growth under mode 1, plane strain, small scale yielding conditions is analyzed. Overall plane strain loading is prescribed, but a full 3D analysis is carried out to model three dimensional microstructural effects. An elastic-viscoplastic constitutive relation for a porous plastic...

Assessment of thin-walled cladding tube mechanical properties by segmented expanding Mandrel test

International Nuclear Information System (INIS)

Nilsson, Karl-Fredrik

2015-01-01

This paper presents the principles of the segmented expanding mandrel test for thin-walled cladding tubes, which can be used as a basic material characterisation test to determine stress-strain curves and ductility or as a test to simulate mechanical pellet-cladding interaction. The paper discusses the strengths and weaknesses of the test method and it illustrates how the test can be used to simulate hydride reorientations in zirconium claddings and quantify how hydride reorientation affects ductility. (authors)

Probing the Statistical Validity of the Ductile-to-Brittle Transition in Metallic Nanowires Using GPU Computing.

Science.gov (United States)

French, William R; Pervaje, Amulya K; Santos, Andrew P; Iacovella, Christopher R; Cummings, Peter T

2013-12-10

We perform a large-scale statistical analysis (>2000 independent simulations) of the elongation and rupture of gold nanowires, probing the validity and scope of the recently proposed ductile-to-brittle transition that occurs with increasing nanowire length [Wu et al. Nano Lett. 2012, 12, 910-914]. To facilitate a high-throughput simulation approach, we implement the second-moment approximation to the tight-binding (TB-SMA) potential within HOOMD-Blue, a molecular dynamics package which runs on massively parallel graphics processing units (GPUs). In a statistical sense, we find that the nanowires obey the ductile-to-brittle model quite well; however, we observe several unexpected features from the simulations that build on our understanding of the ductile-to-brittle transition. First, occasional failure behavior is observed that qualitatively differs from that predicted by the model prediction; this is attributed to stochastic thermal motion of the Au atoms and occurs at temperatures as low as 10 K. In addition, we also find that the ductile-to-brittle model, which was developed using classical dislocation theory, holds for nanowires as small as 3 nm in diameter. Finally, we demonstrate that the nanowire critical length is higher at 298 K relative to 10 K, a result that is not predicted by the ductile-to-brittle model. These results offer practical design strategies for adjusting nanowire failure and structure and also demonstrate that GPU computing is an excellent tool for studies requiring a large number of independent trajectories in order to fully characterize a system's behavior.

Effect of the hydrogen concentration on the ductility of Zry-4; Efecto de la concentracion de hidrogeno sobre la ductilidad de Zry-4

Energy Technology Data Exchange (ETDEWEB)

Domizzi, G; Ovejero Garcia, J [Comision Nacional de Energia Atomica, San Martin (Argentina). Unidad de Actividad Materiales

1997-12-31

After many years in service, zirconium alloys employed in nuclear reactors may reach high contents of hydride particles, exceeding the hydrogen solid solubility at the service temperature. The brittle character of zirconium hydride promotes the alloy embrittlement. In order to predict the critical hydrogen concentration which causes a ductile-brittle transition in a Zry-4 foil, 0.02mm thick, tensile test specimens were hydride by gaseous charging. To obtain uniform hydride distribution the specimens were electroplated with a film of copper prior to gaseous charge. In absence of oxide film, the foils retained its ductility up to high hydrogen concentration (950 Og/g). The critical hydrogen concentration was attained at 2900-3100 Og/g. (author). 4 refs., 2 figs., 1 tab.

Influencing factors on as-cast and heat treated 400-18 ductile iron grade characteristics

Directory of Open Access Journals (Sweden)

I. Riposan

2007-11-01

Full Text Available As-cast and heat-treated 400-18 ductile iron (DI grade was obtained in different foundry conditions, as metallic charge, Mg-treatment alloy and inoculation. It was found that the Pearlitic Influence Factor (Px and Antinodulizing Complex Factor (K1 have an important influence on property of DI, depending on the Mn and P level, the metallurgical quality of iron melt, rare earth (RE and inoculation. It was also found that the influence of Mn is depended on the phosphorus and residual elements level in ductile iron. Less than 0.03%P and 0.2%Mn and Px2.0 determines presence of pearlite in as-cast structure, while ferrite structure is obtained after a short annealing heat treatment. Lower level of phosphorus (P1.2. Si has a significant influence on the mechanical properties of heat treated ductile irons: an important decreasing of elongation level and a moderate increasing of yield and tensile strength and their ratio in 150-170 HB typical hardness field. A typical final chemical composition for as-cast 400-18 ductile iron could include 3.5%-3.7%C, 2.4%-2.5%Si, max.0.18%Mn, max.0.025%P, max.0.01%S, 0.04%-0.05%Mgres. for Px<1.5 and K1<1.1. High purity pig iron, RE-bearing FeSiMg and powerful inoculant are also recommended.

Effect of nonmetallic inclusions on anisotropy of ductility in 35KhN3MFA steel forgings

International Nuclear Information System (INIS)

Shtremel', M.A.; Yavojskij, V.I.; Volkov, V.A.; Chursin, G.M.; Chukhlov, V.I.; Fetisov, G.I.; Mochalin, N.K.; Smol'yaninov, L.V.

1980-01-01

Characteristics of nonmetaltic inclusions and anizotropy of ductility and of impuct strength of forgings of the 35KhN3MFA steel are compared at different variants of melting and outer-furnace treatment. It is shown that method of melting rugulates anisotropy of ductility primarily through deformability of large inclusions during forging. Deformability of inclusions considerably changes due to introduction of silicocalcium in iron mold [ru

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 ...

The semi-brittle to ductile transition in peridotite on oceanic faults: mechanisms and P-T condition

Science.gov (United States)

Prigent, C.; Warren, J. M.; Kohli, A. H.; Teyssier, C. P.

2017-12-01

Experimental and geological-petrological studies suggest that the transition from brittle faulting to ductile flow of olivine, i.e. from seismic to aseismic behavior of mantle rocks (peridotites), occurs close to 600°C. However, recent seismological studies on oceanic transform faults (TFs) and ridges have documented earthquakes to temperatures (T) up to 700-800°C. In this study, we carried out a petrological, microstructural and geochemical analysis of natural samples of peridotites dredged at 3 different oceanic TFs of the Southwest Indian Ridge: Shaka, Prince Edward and Atlantis II. We selected samples displaying variable amounts of ductile deformation (from porphyroclastic tectonites to ultramylonites) prior to serpentinization in order to characterize their relatively high-T mechanical behavior. We find that the most deformed samples record cycles of ductile and brittle deformation. Peridotite ductile flow is characterized by drastic grain size reduction and the development of (ultra)mylonitic shear zones. In these zones, a switch in olivine deformation mechanism from dislocation creep to grain-size sensitive creep is associated with dissolution/precipitation processes. Brittle deformation of these samples is evidenced by the presence of (at least centimetric) transgranular and intragranular fractures that fragment coarser grained minerals. Both kinds of fractures are filled with the same phase assemblage as in the ultramylonitic bands: olivine + amphibole ± orthopyroxene ± Al-phase (plagioclase and/or spinel) ± sulfides. The presence of amphibole indicates that this semi-brittle deformation was assisted by hydrous fluids and its composition (e.g. high concentration of chlorine) suggests that the fluids have most likely a hydrothermal origin. We interpret these fractures to have formed under fluid-assisted conditions, recording paleo-seismic activity that alternated with periods of relatively slow interseismic ductile flow. The presence of Mg

The Influence of the Induced Ferrite and Precipitates of Ti-bearing Steel on the Ductility of Continuous Casting Slab

Science.gov (United States)

Qian, Guoyu; Cheng, Guoguang; Hou, Zibing

2015-11-01

In order to investigate the loss of the ductility of Ti-bearing ship plate steel under 1000 °C, where the ductility begins to reduce rapidly, so the hot ductility of Ti-bearing ship plate steel has been obtained using the Gleeble 1500 thermal-mechanical simulator and also the studies about the effect of grain boundary ferrite films and precipitates containing Ti on the ductility has been carried out. The result showed that the TiN particles precipitating at 950 °C with a larger size and smaller volume fraction cannot effectively suppress the occurrence of recrystallization and the ductility still retains at a high level, although R.A. value presents a certain degree of decline compared with 1000 °C. A large number of smaller Ti(C,N) particles precipitate at 900 °C and can induce the formation of a very small amount of fine grain boundary ferrite, which deteriorates the adhesion strength of the grain boundary, so the R.A. value rapidly reduces to less than 50%. When the temperature falls to close Ae3 (827 °C), the amount of the grain boundary ferrite films increase due to the ferrite phase transformation, but the ferrite film thickness becomes more uneven at the same time, which results in the increase of strain concentration and plays a leading role in causing the decrease of ductility, so the R.A. value has been kept less than 40% as the temperature cooling to 800 °C from 850 °C. When the temperature further decreases, the ductility starts to recover due to the increase of average ferrite film thickness to a greater degree which greatly reduces the strain concentration of the grain boundary.

A roadmap for tailoring the strength and ductility of ferritic/martensitic T91 steel via thermo-mechanical treatment

International Nuclear Information System (INIS)

Song, M.; Sun, C.; Fan, Z.; Chen, Y.; Zhu, R.; Yu, K.Y.; Hartwig, K.T.; Wang, H.; Zhang, X.

2016-01-01

Ferritic/martensitic (F/M) steels with high strength and excellent ductility are important candidate materials for the life extension of the current nuclear reactors and the design of next generation nuclear reactors. Recent studies show that equal channel angular extrusion (ECAE) was able to improve mechanical strength of ferritic T91 steels moderately. Here, we examine several strategies to further enhance the mechanical strength of T91 while maintaining its ductility. Certain thermo-mechanical treatment (TMT) processes enabled by combinations of ECAE, water quench, and tempering may lead to “ductile martensite” with exceptionally high strength in T91 steel. The evolution of microstructures and mechanical properties of T91 steel were investigated in detail, and transition carbides were identified in water quenched T91 steel. This study provides guidelines for tailoring the microstructure and mechanical properties of T91 steel via ECAE enabled TMT for an improved combination of strength and ductility.

Ductility Analysis of RC Beams Considering the Concrete Confinement Effect Produced by the Shear Reinforcement: a Numerical Approach

Directory of Open Access Journals (Sweden)

Caio Gorla Nogueira

Full Text Available Abstract In this paper, a simplified numerical approach to study the influence of the confinement effect provided by transversal reinforcement on the ductility behavior of RC beams in bending is proposed. A unidimensional FEM mechanical model coupled to the Mazars’ damage model to simulate concrete behavior was adopted to assess ductility curvatures at the ultimate limit state. The confinement effect was incorporated to the numerical model through a calibration process of the damage internal parameters, based on the Least Square Method and an analytical law proposed by Kent and Park (1971. Several numerical analyses were carried out considering different designs of RC beams according to a parametric study varying the neutral axis position, concrete compressive strength and the volumetric transversal reinforcement ratio. The obtained results showed the importance of the amount of transversal reinforcement on the ductility behavior, increasing the ductility factor even for the cases with inappropriate neutral axis position.

Highly ductile multilayered films by layer-by-layer assembly of oppositely charged polyurethanes for biomedical applications.

Science.gov (United States)

Podsiadlo, Paul; Qin, Ming; Cuddihy, Meghan; Zhu, Jian; Critchley, Kevin; Kheng, Eugene; Kaushik, Amit K; Qi, Ying; Kim, Hyoung-Sug; Noh, Si-Tae; Arruda, Ellen M; Waas, Anthony M; Kotov, Nicholas A

2009-12-15

Multilayered thin films prepared with the layer-by-layer (LBL) assembly technique are typically "brittle" composites, while many applications such as flexible electronics or biomedical devices would greatly benefit from ductile, and tough nanostructured coatings. Here we present the preparation of highly ductile multilayered films via LBL assembly of oppositely charged polyurethanes. Free-standing films were found to be robust, strong, and tough with ultimate strains as high as 680% and toughness of approximately 30 MJ/m(3). These results are at least 2 orders of magnitude greater than most LBL materials presented until today. In addition to enhanced ductility, the films showed first-order biocompatibility with animal and human cells. Multilayered structures incorporating polyurethanes open up a new research avenue into the preparation of multifunctional nanostructured films with great potential in biomedical applications.

Stiff, light, strong and ductile: nano-structured High Modulus Steel.

Science.gov (United States)

Springer, H; Baron, C; Szczepaniak, A; Uhlenwinkel, V; Raabe, D

2017-06-05

Structural material development for lightweight applications aims at improving the key parameters strength, stiffness and ductility at low density, but these properties are typically mutually exclusive. Here we present how we overcome this trade-off with a new class of nano-structured steel - TiB 2 composites synthesised in-situ via bulk metallurgical spray-forming. Owing to the nano-sized dispersion of the TiB 2 particles of extreme stiffness and low density - obtained by the in-situ formation with rapid solidification kinetics - the new material has the mechanical performance of advanced high strength steels, and a 25% higher stiffness/density ratio than any of the currently used high strength steels, aluminium, magnesium and titanium alloys. This renders this High Modulus Steel the first density-reduced, high stiffness, high strength and yet ductile material which can be produced on an industrial scale. Also ideally suited for 3D printing technology, this material addresses all key requirements for high performance and cost effective lightweight design.

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

African Journals Online (AJOL)

ADI austempered at higher temperature showed better corrosion resistance than the ..... temperature and time on corrosion behaviour of ductile iron in chloride and acidic ... iron ore in ball mills, Transactions of the Indian Institute of Metals, Vol.

Effect of solute grain boundary segregation and hardness on the ductile-to-brittle transition for a Cr-Mo low-alloy steel

International Nuclear Information System (INIS)

Shen, D.-D.; Song, S.-H.; Yuan, Z.-X.; Weng, L.-Q.

2005-01-01

Combined solute grain boundary segregation and hardness effect on the ductile-to-brittle transition is examined for a P-doped 2.25Cr-1Mo steel by means of Auger electron spectroscopy (AES) in conjunction with hardness measurements, Charpy impact tests and scanning electron microscopy (SEM). During ageing at 540 deg. C after water quenching from 980 deg. C, the segregation of phosphorus, molybdenum and chromium increases and the hardness decreases with increasing ageing time. The ductile-to-brittle transition temperature (DBTT) increases with increasing phosphorus segregation and decreases with decreasing hardness. The phosphorus segregation effect is dominant until 100 h ageing and after that the hardness effect becomes dominant, making the DBTT decrease with further increasing ageing time although the segregation of phosphorus still increases strongly. The segregation of molybdenum has some effect on the DBTT decrease

Modelling of liquid sodium induced crack propagation in T91 martensitic steel: Competition with ductile fracture

Energy Technology Data Exchange (ETDEWEB)

Hemery, Samuel [Institut PPRIME, CNRS, Université de Poitiers, ISAE ENSMA, UPR 3346, Téléport 2, 1 Avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Berdin, Clotilde, E-mail: clotilde.berdin@u-psud.fr [Univ Paris-Sud, SP2M-ICMMO, CNRS UMR 8182, F-91405 Orsay Cedex (France); Auger, Thierry; Bourhi, Mariem [Ecole Centrale-Supelec, MSSMat CNRS UMR 8579, F-92295 Chatenay Malabry Cedex (France)

2016-12-01

Liquid metal embrittlement (LME) of T91 steel is numerically modeled by the finite element method to analyse experimental results in an axisymmetric notched geometry. The behavior of the material is identified from tensile tests then a crack with a constant crack velocity is introduced using the node release technique in order to simulate the brittle crack induced by LME. A good agreement between the simulated and the experimental macroscopic behavior is found: this suggests that the assumption of a constant crack velocity is correct. Mechanical fields during the embrittlement process are then extracted from the results of the finite element model. An analysis of the crack initiation and propagation stages: the ductile fracture probably breaks off the LME induced brittle fracture. - Highlights: • T91 martensitic steel is embrittled by liquid sodium depending on the loading rate at 573 K. • The mechanical behavior is modeled by a von Mises elastic-plastic law. • The LME induced crack propagates at a constant velocity. • The mechanical state at the crack tip does not explain a brittle crack arrest. • The occurrence of the ductile fracture breaks off the brittle fracture.

Ductility Enhancement of Post-Northridge Connections by Multilongitudinal Voids in the Beam Web

Directory of Open Access Journals (Sweden)

Sepanta Naimi

2013-01-01

Full Text Available Since the earthquakes in Northridge and Kobe in 1994 and 1995, respectively, many investigations have been carried out towards improving the strength and ductility of steel beam to column pre- and post-Northridge connections. In order to achieve these objectives, recent researches are mainly focused on three principles: reducing the beam section to improve the beam ductility, adding different kinds of slit damper to beam and column flanges to absorb and dissipate the input earthquake energy in the connection and strengthening the connection area using additional elements such as rib plates, cover plates, and flange plates to keep the plastic hinges away from the column face. This paper presents a reduced beam section approach via the introduction of multilongitudinal voids (MLV in the beam web for various beam depths varying from 450 mm to 912 mm. ANSYS finite element program was used to simulate the three different sizes of SAC sections: SAC3, SAC5, and SAC7. Results showed an improvement in the connection ductility since the input energy was dissipated uniformly along the beam length and the total rotation of the connection was over four percent radian.

Brittle-to-ductile transition of lithiated silicon electrodes: Crazing to stable nanopore growth.

Science.gov (United States)

Wang, Haoran; Wang, Xueju; Xia, Shuman; Chew, Huck Beng

2015-09-14

Using first principle calculations, we uncover the underlying mechanisms explaining the brittle-to-ductile transition of LixSi electrodes in lithium ion batteries with increasing Li content. We show that plasticity initiates at x = ∼ 0.5 with the formation of a craze-like network of nanopores separated by Si-Si bonds, while subsequent failure is still brittle-like with the breaking of Si-Si bonds. Transition to ductile behavior occurs at x ⩾ 1 due to the increased density of highly stretchable Li-Li bonds, which delays nanopore formation and stabilizes nanopore growth. Collapse of the nanopores during unloading of the LixSi alloys leads to significant strain recovery.

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)

Effects of retained austenite volume fraction, morphology, and carbon content on strength and ductility of nanostructured TRIP-assisted steels

Energy Technology Data Exchange (ETDEWEB)

Shen, Y.F., E-mail: shenyf@smm.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, 3 Wenhua Road, Shenyang 110004 (China); Qiu, L.N. [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, 3 Wenhua Road, Shenyang 110004 (China); Sun, X. [Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352 (United States); Zuo, L. [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, 3 Wenhua Road, Shenyang 110004 (China); Liaw, P.K. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 (United States); Raabe, D. [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 8, 40237 Düsseldorf (Germany)

2015-06-11

With a suite of multi-modal and multi-scale characterization techniques, the present study unambiguously proves that a substantially-improved combination of ultrahigh strength and good ductility can be achieved by tailoring the volume fraction, morphology, and carbon content of the retained austenite (RA) in a transformation-induced-plasticity (TRIP) steel with the nominal chemical composition of 0.19C–0.30Si–1.76Mn–1.52Al (weight percent, wt%). After intercritical annealing and bainitic holding, a combination of ultimate tensile strength (UTS) of 1100 MPa and true strain of 50% has been obtained, as a result of the ultrafine RA lamellae, which are alternately arranged in the bainitic ferrite around junction regions of ferrite grains. For reference, specimens with a blocky RA, prepared without the bainitic holding, yield a low ductility (35%) and a low UTS (800 MPa). The volume fraction, morphology, and carbon content of RA have been characterized using various techniques, including the magnetic probing, scanning electron microscopy (SEM), electron-backscatter-diffraction (EBSD), and transmission electron microscopy (TEM). Interrupted tensile tests, mapped using EBSD in conjunction with the kernel average misorientation (KAM) analysis, reveal that the lamellar RA is the governing microstructure component responsible for the higher mechanical stability, compared to the blocky one. By coupling these various techniques, we quantitatively demonstrate that in addition to the RA volume fraction, its morphology and carbon content are equally important in optimizing the strength and ductility of TRIP-assisted steels.

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...

Ductile alloys for sealing modular component interfaces

Science.gov (United States)

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).

Ductile Damage Evolution and Strain Path Dependency

International Nuclear Information System (INIS)

Tasan, C. C.; Hoefnagels, J. M. P.; Peerlings, R. H. J.; Geers, M. G. D.; ten Horn, C. H. L. J.; Vegter, H.

2007-01-01

Forming limit diagrams are commonly used in sheet metal industry to define the safe forming regions. These diagrams are built to define the necking strains of sheet metals. However, with the rise in the popularity of advance high strength steels, ductile fracture through damage evolution has also emerged as an important parameter in the determination of limit strains. In this work, damage evolution in two different steels used in the automotive industry is examined to observe the relationship between damage evolution and the strain path that is followed during the forming operation

Effects of boron additions and solutionizing treatments on microstructures and ductility of forged Ti–6Al–4V alloys

International Nuclear Information System (INIS)

Luan, J.H.; Jiao, Z.B.; Chen, G.; Liu, C.T.

2015-01-01

Highlights: • Proper boron additions and heat-treatments improve the ductility of Ti64 alloys. • Coarse TiB precipitates embrittle the Ti64 alloys causing ductility loss. • Modified Ti64 forged alloys with high strength and high ductility are developed. - Abstract: The effects of boron additions on the microstructure and mechanical properties of forged Ti–6Al–4V alloys in different heat-treatment conditions have been characterized by both experimental studies and thermodynamic calculations. The results indicate a combination of proper post-forging treatments and B additions are helpful for control of the prior-β grain size and the volume fraction of α phase, thereby tuning the ductility of the forged Ti–6Al–4V alloys. However, the B-containing alloys exhibit a significant drop in ductility if the solutionizing temperature is too high, and this embrittlement is mainly due to the coarsening of brittle TiB borides. The mechanism in this case is due to the cleavage fracture of TiB rather than its debonding with the matrix, as indicated by the observation of the aligned TiB borides on the matching areas of both halves of the fracture surfaces. Thus, the TiB size and orientation, the prior-β grain size, and the volume fraction of the α phase all play important roles in controlling the mechanical properties of the forged Ti–6Al–4V alloys. The current findings shed light on the composition–microstructure–ductility relationship in the forged Ti–6Al–4V alloys

Effects of boron additions and solutionizing treatments on microstructures and ductility of forged Ti–6Al–4V alloys

Energy Technology Data Exchange (ETDEWEB)

Luan, J.H.; Jiao, Z.B. [Center for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, College of Science and Engineering, City University of Hong Kong, Hong Kong (China); Chen, G. [Engineering Research Center of Materials Behavior and Design, Ministry of Education, Nanjing University of Science and Technology, Nanjing 210094 (China); Liu, C.T., E-mail: chainliu@cityu.edu.hk [Center for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, College of Science and Engineering, City University of Hong Kong, Hong Kong (China)

2015-03-05

Highlights: • Proper boron additions and heat-treatments improve the ductility of Ti64 alloys. • Coarse TiB precipitates embrittle the Ti64 alloys causing ductility loss. • Modified Ti64 forged alloys with high strength and high ductility are developed. - Abstract: The effects of boron additions on the microstructure and mechanical properties of forged Ti–6Al–4V alloys in different heat-treatment conditions have been characterized by both experimental studies and thermodynamic calculations. The results indicate a combination of proper post-forging treatments and B additions are helpful for control of the prior-β grain size and the volume fraction of α phase, thereby tuning the ductility of the forged Ti–6Al–4V alloys. However, the B-containing alloys exhibit a significant drop in ductility if the solutionizing temperature is too high, and this embrittlement is mainly due to the coarsening of brittle TiB borides. The mechanism in this case is due to the cleavage fracture of TiB rather than its debonding with the matrix, as indicated by the observation of the aligned TiB borides on the matching areas of both halves of the fracture surfaces. Thus, the TiB size and orientation, the prior-β grain size, and the volume fraction of the α phase all play important roles in controlling the mechanical properties of the forged Ti–6Al–4V alloys. The current findings shed light on the composition–microstructure–ductility relationship in the forged Ti–6Al–4V alloys.

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.

Cohesive traction–separation laws for tearing of ductile metal plates

DEFF Research Database (Denmark)

Nielsen, Kim Lau; Hutchinson, John W.

2012-01-01

The failure process ahead of a mode I crack advancing in a ductile thin metal plate or sheet produces plastic dissipation through a sequence of deformation steps that include necking well ahead of the crack tip and shear localization followed by a slant fracture in the necked region somewhat clos...

The prediction of creep damage in Type 347 weld metal: part II creep fatigue tests

International Nuclear Information System (INIS)

Spindler, M.W.

2005-01-01

Calculations of creep damage under conditions of strain control are often carried out using either a time fraction approach or a ductility exhaustion approach. In part I of this paper the rupture strength and creep ductility data for a Type 347 weld metal were fitted to provide the material properties that are used to calculate creep damage. Part II of this paper examines whether the time fraction approach or the ductility exhaustion approach gives the better predictions of creep damage in creep-fatigue tests on the same Type 347 weld metal. In addition, a new creep damage model, which was developed by removing some of the simplifying assumptions that are made in the ductility exhaustion approach, was used. This new creep damage model is a function of the strain rate, stress and temperature and was derived from creep and constant strain rate test data using a reverse modelling technique (see part I of this paper). It is shown that the new creep damage model gives better predictions of creep damage in the creep-fatigue tests than the time fraction and the ductility exhaustion approaches

Simultaneous enhancement of strength and ductility in cryogenically treated AISI D2 tool steel

Energy Technology Data Exchange (ETDEWEB)

Ghasemi-Nanesa, Hadi; Jahazi, Mohammad, E-mail: mohammad.jahazi@etsmtl.ca

2014-03-01

In this research, the effect of cryogenic treatment on microstructural evolution and mechanical properties enhancement of AISI D2 tool steel was investigated. Cryogenic treatment down to liquid nitrogen temperature (77 K) was added to the conventional heat treatment between hardening and tempering steps. Electron microscopy investigation showed higher volume fraction of fine carbides with average diameter below 1 μm indicating effective retardation in carbide coarsening process as a results of cryogenic treatment. A modification in types of carbides was also observed after cryogenic treatment. X-ray diffraction diagrams revealed transformation of retained austenite to martensite at cryogenic temperature. Weakening or removal of carbides peak in the X-ray diagram was considered as evidence of carbides different behavior at cryogenic temperature. Mechanical testing results indicated higher ultimate tensile strength, better ductility, and higher elastic modulus after cryogenic treatment. Analysis of stress–strain diagrams revealed different strain hardening behavior for cryogenically treated alloy when compared to the conventionally heat treated one. Fractography results confirmed strain hardening behavior and showed cleavage fracture for conventionally treated alloy but mixed cleavage–ductile fracture mode for cryogenically treated alloy. The improved mechanical properties after cryogenic treatment are interpreted in terms of the influence of higher volume fraction and uniform distribution of fine carbides in reducing the average active dislocations length and enhancement of the flow stress at any given plastic strain.

Simultaneous enhancement of strength and ductility in cryogenically treated AISI D2 tool steel

International Nuclear Information System (INIS)

Ghasemi-Nanesa, Hadi; Jahazi, Mohammad

2014-01-01

In this research, the effect of cryogenic treatment on microstructural evolution and mechanical properties enhancement of AISI D2 tool steel was investigated. Cryogenic treatment down to liquid nitrogen temperature (77 K) was added to the conventional heat treatment between hardening and tempering steps. Electron microscopy investigation showed higher volume fraction of fine carbides with average diameter below 1 μm indicating effective retardation in carbide coarsening process as a results of cryogenic treatment. A modification in types of carbides was also observed after cryogenic treatment. X-ray diffraction diagrams revealed transformation of retained austenite to martensite at cryogenic temperature. Weakening or removal of carbides peak in the X-ray diagram was considered as evidence of carbides different behavior at cryogenic temperature. Mechanical testing results indicated higher ultimate tensile strength, better ductility, and higher elastic modulus after cryogenic treatment. Analysis of stress–strain diagrams revealed different strain hardening behavior for cryogenically treated alloy when compared to the conventionally heat treated one. Fractography results confirmed strain hardening behavior and showed cleavage fracture for conventionally treated alloy but mixed cleavage–ductile fracture mode for cryogenically treated alloy. The improved mechanical properties after cryogenic treatment are interpreted in terms of the influence of higher volume fraction and uniform distribution of fine carbides in reducing the average active dislocations length and enhancement of the flow stress at any given plastic strain

Fatigue properties of ductile cast iron containing chunky graphite

Energy Technology Data Exchange (ETDEWEB)

Ferro, P., E-mail: ferro@gest.unipd.it [Department of Management and Engineering, University of Padova, Stradella S. Nicola 3, I-36100 Vicenza (Italy); Lazzarin, P.; Berto, F. [Department of Management and Engineering, University of Padova, Stradella S. Nicola 3, I-36100 Vicenza (Italy)

2012-09-30

Highlights: Black-Right-Pointing-Pointer Experimental determination of high cycle fatigue properties of EN-GJS-400. Black-Right-Pointing-Pointer Evaluation of the influence of chunky graphite morphology on fatigue life. Black-Right-Pointing-Pointer Metallurgical analysis and microstructural parameters determination. Black-Right-Pointing-Pointer Nodule counting and nodularity rating. - Abstract: This work deals with experimental determination of high cycle fatigue properties of EN-GJS-400 ductile cast iron containing chunky graphite. Constant amplitude axial tests were performed at room temperature under a nominal load ratio R = 0. In order to evaluate the influence of chunky graphite morphology on fatigue life, fatigue tests were carried out also on a second set of specimens without this microstructural defect. All samples were taken from the core of a large casting component. Metallurgical analyses were performed on all the samples and some important microstructural parameters (nodule count and nodularity rating, among others) were measured and compared. It was found that a mean content of 40% of chunky graphite in the microstructure (with respect to total graphite content) does not influence significantly the fatigue strength properties of the analysed cast iron. Such result was attributed to the presence of microporosity detected on the surface fracture of the specimens by means of electron scanning microscope.

Fatigue properties of ductile cast iron containing chunky graphite

International Nuclear Information System (INIS)

Ferro, P.; Lazzarin, P.; Berto, F.

2012-01-01

Highlights: ► Experimental determination of high cycle fatigue properties of EN-GJS-400. ► Evaluation of the influence of chunky graphite morphology on fatigue life. ► Metallurgical analysis and microstructural parameters determination. ► Nodule counting and nodularity rating. - Abstract: This work deals with experimental determination of high cycle fatigue properties of EN-GJS-400 ductile cast iron containing chunky graphite. Constant amplitude axial tests were performed at room temperature under a nominal load ratio R = 0. In order to evaluate the influence of chunky graphite morphology on fatigue life, fatigue tests were carried out also on a second set of specimens without this microstructural defect. All samples were taken from the core of a large casting component. Metallurgical analyses were performed on all the samples and some important microstructural parameters (nodule count and nodularity rating, among others) were measured and compared. It was found that a mean content of 40% of chunky graphite in the microstructure (with respect to total graphite content) does not influence significantly the fatigue strength properties of the analysed cast iron. Such result was attributed to the presence of microporosity detected on the surface fracture of the specimens by means of electron scanning microscope.

Technical note 2. A review of the creep ductility of copper for nuclear waste canister application

International Nuclear Information System (INIS)

Pettersson, Kjell

2011-03-01

Background: The Swedish Radiation Safety Authority (SSM) reviews the Swedish Nuclear Fuel Company's (SKB) applications under the Act on Nuclear Activities (SFS 1984:3) for the construction and operation of a repository for spent nuclear fuel and for an encapsulation facility. As part of the review, SSM commissions consultants to carry out work in order to obtain information on specific issues. The results from the consultants' tasks are reported in SSM's Technical Note series. Objectives of the project: This project is part of SSM:s review of SKB:s license application for final disposal of spent nuclear fuel. The assignment concerns review of creep mechanisms for copper material used as a corrosion barrier in canisters for nal disposal of nuclear fuel in Sweden. Summary by the author: SKB has presented insufficient evidence to justify their position that the OFP copper has an adequate creep ductility during long term storage. Their large body of experiments only serves to prove that the creep ductility is sufficient for much shorter time spans than the intended storage times. There is a clear need for a credible theory of creep brittleness of OFP copper which will permit extrapolations to long term storage. The theory presented by SKB does not in its present state permit credible extrapolations. Alternatively SKB needs to find an explanation to the effect of phosphorus on the creep ductility and that it ensures the absence of creep brittleness in OFP copper. It is interesting to note that SKB has presented experimental evidence that intergranular cracks can form in OFP material tested in cracked specimens. Perhaps it is possible to more systematically study formation and growth of intergranular cracks in specimens of OFP copper with cracks

Simultaneously enhanced strength and ductility for 3D-printed stainless steel 316L by selective laser melting

Science.gov (United States)

Sun, Zhongji; Tan, Xipeng; Tor, Shu Beng; Chua, Chee Kai

2018-04-01

Laser-based powder-bed fusion additive manufacturing or three-dimensional printing technology has gained tremendous attention due to its controllable, digital, and automated manufacturing process, which can afford a refined microstructure and superior strength. However, it is a major challenge to additively manufacture metal parts with satisfactory ductility and toughness. Here we report a novel selective laser melting process to simultaneously enhance the strength and ductility of stainless steel 316L by in-process engineering its microstructure into a crystallographic texture. We find that the tensile strength and ductility of SLM-built stainless steel 316L samples could be enhanced by 16% and 40% respectively, with the engineered textured microstructure compared to the common textured microstructure. This is because the favorable nano-twinning mechanism was significantly more activated in the textured stainless steel 316L samples during plastic deformation. In addition, kinetic simulations were performed to unveil the relationship between the melt pool geometry and crystallographic texture. The new additive manufacturing strategy of engineering the crystallographic texture can be applied to other metals and alloys with twinning-induced plasticity. This work paves the way to additively manufacture metal parts with high strength and high ductility.

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.

Seismic Performance of High-Ductile Fiber-Reinforced Concrete Short Columns

Directory of Open Access Journals (Sweden)

Mingke Deng

2018-01-01

Full Text Available This study mainly aims to investigate the effectiveness of high-ductile fiber-reinforced concrete (HDC as a means to enhance the seismic performance of short columns. Six HDC short columns and one reinforced concrete (RC short column were designed and tested under lateral cyclic loading. The influence of the material type (concrete or HDC, axial load, stirrup ratio, and shear span ratio on crack patterns, hysteresis behavior, shear strength, deformation capacity, energy dissipation, and stiffness degradation was presented and discussed, respectively. The test results show that the RC short column failed in brittle shear with poor energy dissipation, while using HDC to replace concrete can effectively improve the seismic behavior of the short columns. Compared with the RC short column, the shear strength of HDC specimens was improved by 12.6–30.2%, and the drift ratio and the energy dissipation increases were 56.9–88.5% and 237.7–336.7%, respectively, at the ultimate displacement. Additionally, the prediction model of the shear strength for RC columns based on GB50010-2010 (Chinese code can be safely adopted to evaluate the shear strength of HDC short columns.

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...

Development and application of an environmentally friendly ductile alkali-activated composite

NARCIS (Netherlands)

Nedeljkovic, M.; Lukovic, M.; van Breugel, K.; Hordijk, D.A.; Ye, G.

2018-01-01

This paper presents a development of a ductile alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) based composite as an environmentally friendly material for structural concrete application. For this purpose, polyvinyl alcohol (PVA) fibres and sand aggregate were

Effect of Feeder Configuration on the Microstructure of Ductile Cast Iron

DEFF Research Database (Denmark)

Vedel-Smith, Nikolaj Kjelgaard; Tiedje, Niels Skat

2014-01-01

influence the soundness of different sections of the castings. Moreover, the microstructural changes due to variations in thermal gradients are classified, and the variations in the mushy zone described. The paper discusses how solidification and segregation influence porosity and microstructure of ductile...

Microstructural characteristics of Al-alloyed austempered ductile irons