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排序方式: 共有131条查询结果,搜索用时 193 毫秒
51.
Wei-Sheng Lei 《哲学杂志》2016,96(35):3586-3631
The well established consensus that cleavage fracture is preceded by plastic deformation in structural steels implies that plastic yielding is the threshold stress state for a volume element to incur cleavage fracture. An accurate compliance with this consensus underlies the normalisation of cumulative cleavage fracture probability and the justification of constraint effect on cleavage fracture. These understandings lead to the proposal of a framework for statistical modelling of cleavage fracture in structural steels. The framework takes the spatial microcrack distribution into account to formulate the cumulative failure probability model that allows for a pertinent physical interpretation of Weibull statistics, and derives the fracture probability of an elemental volume in conformity with the yielding condition from a set of commonly adopted microcrack size or strength distributions. Alternative approaches to calibrating model parameters are suggested based on frequency analysis of brittle particles as cleavage initiators and on statistical analysis of cleavage fracture stress. The strict adherence to plastic yielding as a prerequisite to cleavage fracture also reveals the probabilistic nature of notch brittleness and ductile-to-brittle transition behaviour. 相似文献
52.
Correlative atomic scale characterisation of secondary carbides in M50 bearing steel 总被引:1,自引:0,他引:1
Sarah E. Hopkin Mohsen Danaie Gael Guetard Pedro Rivera-Diaz-del-Castillo Paul A. J. Bagot 《哲学杂志》2018,98(9):766-782
Correlative atom probe tomography (APT) and transmission electron microscopy (TEM) are used to characterise the microstructure and chemistry of carbide precipitation in M50 bearing steel. This is a prerequisite in establishing relationships between the microstructure and hydrogen embrittlement (HE) resistance. Secondary carbides are the focus of this study, as they play a major role in improving HE-resistance. Secondary carbides are observed in APT, with compositions close to M4C3, M2C and M3C. Correlative TEM measured orientation relationships between the martensite matrix and carbides, enabling the confirmation of M3C cementite precipitates in the corresponding APT reconstruction. Additionally, other precipitates observed in TEM were correlated to the M2C carbides in APT data. The M4C3 carbides are found to have a significantly lower volume fraction than the M2C carbides. 相似文献
53.
The limiting stresses are determined and constant fatigue life diagrams for high-cycle torsion with repeated stress cycle
are plotted using the limiting-state models obtained based on the hypothesis of a unified constant-life diagram, which is
invariant to the number of cycles to failure. The unified constant-life diagram is given by a transcendental power function
whose exponent is an additional parameter characterizing the sensitivity of the material to the asymmetry of the stress cycle.
The calculated results and experimental data for carbon and alloyed steels and composite materials are in good agreement
__________
Translated from Prikladnaya Mekhanika, Vol. 44, No. 2, pp. 19–28, February 2008. 相似文献
54.
R. L. Klueh 《哲学杂志》2018,98(28):2618-2636
Ferritic/martensitic steels show exceptional void-swelling resistance during neutron irradiation compared to conventional austenitic stainless steels, such as Types 316 and 304. Explanations for the difference have been proposed based on the different crystal structures and the different microstructures of the steels. In this paper, swelling behaviour of ferritic/martensitic steels HT9 and modified 9Cr–Mo are analysed to demonstrate how the complicated tempered martensite microstructure determines their excellent swelling resistance. The variation in steady-state swelling rate observed for different heats and different heat treatments is explained in terms of how chemical composition and heat treatment affect the microstructure. Microstructures of these steels are characteristically non-uniform, containing precipitate-rich and precipitate-deficient regions. Swelling resistance increases as number and size of precipitate-deficient regions are reduced by proper heat treatment. 相似文献
55.
P. Jussila H. Ali‐Löytty K. Lahtonen M. Hirsimäki M. Valden 《Surface and interface analysis : SIA》2010,42(3):157-164
The adsorption of 3‐aminopropyltrimethoxysilane thin films on Fe? 18Cr? 7Mn? 3Ni (austenitic stainless steel) was investigated by X‐ray photoelectron spectroscopy (XPS) and inelastic electron background analysis. The bonding and morphology of the films were strongly dependent on the surface hydroxyl concentration, which was controlled by the oxidation pretreatment of the substrate. In particular, an aminopropylsilane (APS) monolayer with high degree of bonding to the substrate was obtained on an electrochemically passivated surface with very high hydroxyl concentration. On the other hand, the deposition of weakly bound APS clusters was observed on substrates having relatively low hydroxyl concentrations. The adsorption occurred initially via hydrogen bonding, whereas heating to 373 K resulted in the formation of covalent Si? O? M bonds at the silane/metal oxide interface. The results of this study provide insight into the interaction between silanes and stainless steels surfaces, and can be applied for functionalization of stainless steel materials in an extensive range of applications. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
56.
《Analytical letters》2012,45(9):465-471
Abstract An atomic fluorescence spectroscopic method is described for the assay of silicon in low alloy steels. The method reported is more sensitive than the corresponding atomic absorption method, the detection limit being 0.7 ppm at 351.6 nm compared to 4 ppm for atomic absorption at the same wavelength. 相似文献
57.
《Analytical letters》2012,45(6):1022-1037
Abstract A rapid, simple, sensitive, and selective spectrophotometric method is investigated for the determination of traces of vanadium (V) in foodstuffs, alloy steels, and pharmaceutical, water, soil, and urine samples in aqueous DMF medium. The metal ion forms a green colored complex with 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) in an acidic buffer of pH 6.0. The green colored solution, having an absorbance maximum at 380 nm, is stable for more than 72 hours. Beer's law is obeyed in the range of 0.051–2.037 µg ml?1. The molar absorptivity and Sandell's sensitivity of the method are found as 2.75 × 104 l mol?1 cm?1 and 0.0018 µg cm?2, respectively. The green colored complex has 1:2 [V(V)-HMBATSC] stoichiometry. The stability constant of the complex is determined as 3.267 × 1011 by Job's method. The optimum reaction conditions and other analytical parameters are studied. A sensitive and selective second-order derivative spectrophotometry has also been proposed for the determination of V(V). The interference of various cations and anions are studied. The present method is successfully applied to the determination of vanadium (V) in foodstuffs, alloy steels, and pharmaceutical, water, soil, and urine samples. 相似文献
58.
建立了双道氢化物发生-原子荧光光谱法同时测定核电用钢中痕量砷和锑的新方法。用王水溶解样品,以2.0 g/L L-半胱氨酸溶液作为预还原剂,在低酸度条件下实现对砷、锑的预还原。用20 g/L硼氢化钾溶液作为还原剂,氢化物发生反应在0.5 mol/L乙酸介质中进行。砷、锑的质量浓度在40μg/L范围与相应的荧光强度呈线性关系,方法的检出限(3s/k)分别为0.032μg/L和0.022μg/L。应用此方法同时测定了核电用钢及不锈钢标准样品中的砷锑含量,并与电感耦合等离子体原子发射光谱法的分析结果作了对比,测定值与标准样品的标准值相符,结果的相对标准偏差(n=8)均小于5.0%。 相似文献
59.
An atom probe study has been performed on 15Kh2MFA base and 10KhMFT weld metal surveillance specimens from a VVER-440/213C reactor to investigate the mechanisms that produce embrittlement in low copper materials during service. The composition of the base metal was Fe-0.06 at.% Cu, 3.1% Cr, 0.34% V, 0.46% Mn, 0.35% Mo, 0.07% Ni, 0.34% Si, 0.74% C, 0.025% P, and 0.028% S. The base material was characterized after thermal aging for 10 years at 295°C and after neutron irradiation at 270°C for 10 years to a fluence of 1.0×1025 m−2 (E>0.5 MeV). The ductile-to-brittle transition temperatures (DBTT) of the base metal were −49, −70 and 141°C, for the unirradiated, thermally aged and neutron irradiated conditions, respectively. The composition of the weld metal was Fe-0.05 at.% Cu, 1.46% Cr, 0.22% V, 1.11% Mn, 0.29% Mo, 1.17% Si, 0.17% C, 0.02% P, and 0.029% S. The weld material was characterized after tempering for 18 h at 690°C plus a simulated stress relief treatment of 43.5 h at 680°C, after thermal aging for 5 years at 295°C, and after neutron irradiation at 275°C for 5 years to a fluence of 5.2×1024 m2 (E>0.5 MeV). The DBTTs were 7, 11 and 123°C, respectively, for these three conditions. A high number density of ultrafine manganese- and silicon-enriched regions was observed in both neutron-irradiated materials. Phosphorus segregation was observed at the VC-matrix interface and at grain boundaries. 相似文献
60.
Mario Carpentieri Giovanni Finocchio Fabio La Foresta Bruno Azzerboni 《Journal of magnetism and magnetic materials》2004,280(2-3):158-163
The problem of modeling the magnetic behavior due to a magnetization process is usually dealt with using the classical scalar Preisach model (CSPM). Recently, it has been shown that in the case of soft magnetic materials better results can be obtained by means of the modified scalar Preisach model (MSPM). The problem of model identification is common to both these two approaches. In the past we used a Lorentzian approximation for CSPM identification. In this paper, after reviewing the method, which allows, in particular, the efficient determination of the parameters controlling the reversible magnetization, we propose an extension of the Lorentzian approximation to the case of MSPM identification. It will be shown that an accurate estimation of the model parameters is possible also in this case, as it is confirmed by comparing the model with experimental data. 相似文献