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  • 1
    Electronic Resource
    Electronic Resource
    Estimations of creep fracture mechanics parameters for through-thickness cracked cylinders and finite element validation (2003)
    Oxford, UK : Blackwell Science, Ltd
    Fatigue & fracture of engineering materials & structures 26 (2003), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper compares engineering estimation schemes of C* and creep crack opening displacement (COD) for cylinders with circumferential and axial through-thickness cracks at elevated temperatures with detailed 3D elastic-creep finite element results. Engineering estimation schemes include the GE/EPRI method; the reference stress (RS) method where the reference stress is defined based on the plastic limit load; and the enhanced reference stress (ERS) method where the reference stress is defined based on the optimised reference load, recently proposed by the authors. Systematic investigations are made not only on the effect of creep-deformation behaviour on C* and creep COD, but also on effects of the crack location, the cylinder geometry, the crack length and the loading mode. Comparison of the finite element (FE) results with engineering estimations provides that for idealised power law creep, estimated C* and COD rate results from the GE/EPRI method agree best with FE results, suggesting that published plastic influence functions for plastic J and COD for through-thickness cracked cylinders are reliable. For general creep-deformation laws where either primary or tertiary creep is important and thus the GE/EPRI method is hard to apply, on the other hand, the ERS method provides more accurate and robust estimations for C* and COD rate than the reference stress method. As these two methods differ only in the definition of the reference stress, the ERS method maintains benefits of the reference stress method in terms of simplicity, but improves accuracy of the estimated J, C* and COD results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.2003.00623.x
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  • 2
    Electronic Resource
    Electronic Resource
    Numerical investigation on J-integral testing of heterogeneous fracture toughness testing specimens: Part I – weld metal cracks (2003)
    PO Box 1354, 9600 Garsington Road, Oxford OX4 2XG, UK. : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 26 (2003), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Based on extensive two-dimensional (2D) finite element (FE) analyses, the present work provides the plastic η factor solutions for fracture toughness J-integral testing of heterogeneous specimens with weldments. Solutions cover practically interesting ranges of strength mismatch and relative weld width, and are given for three typical geometries for toughness testing: a middle cracked tension (M(T)) specimen, single edge cracked bend (SE(B)) specimen and (C(T)) specimen. For mismatched M(T) specimens, both plane strain and plane stress conditions are considered, whereas for SE(B) and C(T) specimens, only the plane strain condition is considered. For all cases, only deep cracks are considered, and an idealized butt weld configuration is considered, where the weld metal strip has a rectangular cross section. Based on the present solutions for the strength mismatch effect on plastic η factors, a window is provided, within which the homogeneous J estimation procedure can be used for weldment toughness testing. The effect of the weld groove configuration on the plastic η factor is briefly discussed, concluding the need for further systematic analysis to provide guidance to practical toughness testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.2003.00676.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Lüders strain on engineering crack opening displacement estimations for leak-before-break analysis: finite element study (2001)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 24 (2001), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: As a companion paper to our previous paper [Fatigue Fract. Engng Mater. Struct. 24, 243–254], this note provides further validation on the engineering crack opening displacement (COD) estimation equation based on the enhanced reference stress method against three-dimensional, elastic–plastic finite element (FE) results using actual tensile data of three typical ferritic steels exhibiting a wide range of Lüders strain. Furthermore, the resulting FE results are also compared with the GE/EPRI COD predictions. It is found that the proposed enhanced reference stress method gives overall more accurate and robust COD results than the GE/EPRI method, compared with the FE results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.2001.00432.x
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced reference stress-based J and crack opening displacement estimation method for leak-before-break analysis and comparison with GE.EPRI method (2001)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 24 (2001), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Three-dimensional, elastic–plastic finite element analyses for circumferential through-wall cracked pipes are performed using actual tensile data of stainless steels, for two purposes. The first one is to validate the recently proposed enhanced reference stress (ERS) method to estimate the J-integral and rack-opening displacement (COD) for circumferential through-wall cracked pipes. The second one is to compare the J and COD results from the ERS method with those based on the GE/EPRI method, together with the finite element results. It is found that the GE/EPRI method generally provides poor estimations of J and COD, and such poor estimation results from the Ramberg–Osgood (R–O) fit. Moreover, the GE/EPRI results can be very sensitive to how the stress–strain data are fitted using the R–O relation. The most appropriate fitting range for the R–O fit depends on the material, and thus no specific guideline can be given. On the contrary, the J and COD estimations based on the ERS method give more accurate and robust results than the GE/EPRI estimation. The present results, together with the experimental validation presented in the previous paper, provide sufficient confidence in using the proposed method in the leak-before-break analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.2001.00388.x
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  • 5
    Electronic Resource
    Electronic Resource
    Formation of a metastable ferromagnetic τ phase during containerless melt processing and rapid quenching in Mn-Al-C alloys (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 676-680 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Solidification of selected Mn-Al-C alloys during containerless levitation and rapid quenching has yielded the first report for a ferromagnetic metastable τ (L10) phase formed directly from the melt. Complete solidification to τ phase was interrupted by the competitive evolution of an equilibrium ε phase during recalescence. The amount of undercooling required to produce the metastable ferromagnetic τ phase in a Mn0.55Al0.433C0.017 alloy during solidification was estimated as approximately 470 K based on differential thermal analysis results. When the alloy carbon content was increased to 3.4 at. % (i.e., Mn0.55Al0.416Co0.034 alloy), a transition in structure development occurred so that the samples exhibited γ2 phase formation as well as τ and ε phases. Both microstructural observations and x-ray diffraction examination were used to guide the interpretation and the analysis of solidification pathways. The attainment of the high liquid undercooling required to nucleate the metastable τ phase from the melt may be facilitated by containerless processing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351326
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  • 6
    Electronic Resource
    Electronic Resource
    Thermodynamics and kinetics of the undercooled liquid and the glass transition of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 alloy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4039-4043 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Differential scanning calorimetry (DSC) was used to determine the thermodynamic functions of the undercooled liquid and the amorphous phase with respect to the crystalline state of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass forming alloy. The specific heat capacities of this alloy in the undercooled liquid, the amorphous state and the crystal were determined. The differences in enthalpy, ΔH, entropy, ΔS, and Gibbs free energy, ΔG, between crystal and the undercooled liquid were calculated using the measured specific heat capacity data as well as the heat of fusion. The results indicate that the Gibbs free energy difference between metastable undercooled liquid and crystalline solid, ΔG, stays small compared to conventional metallic glass forming alloys even for large undercoolings. Furthermore, the Kauzmann temperature, TK, where the entropy of the undercooled liquid equals to that of the crystal, was determined to be 560 K. The Kauzmann temperature is compared with the experimentally observed rate-dependent glass transition temperature, Tg. Both onset and end temperatures of the glass transition depend linearly on the logarithm of the heating rate based on the DSC experiments. Those characteristic temperatures for the kinetically observed glass transition become equal close to the Kauzmann temperature in this alloy, which suggests an underlying thermodynamic glass transition as a lower bound for the kinetically observed freezing process. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359485
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of rolling conditions on microstructure and magnetic properties of thin gauged 3% Si–Fe sheets (abstract) : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4115-4115 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To match the requirements for development of transformer cores with lower iron losses, many new materials are under development including amorphous materials, 6.5% Si–Fe sheets and thin gauged 3% Si–Fe sheets. Among these materials, the thin gauged 3% Si–Fe sheets are attracting attention due to their good magnetic properties and scientific interest. Arai et al. reported that the magnetic properties of the sheets were comparable to those of the amorphous materials and (110)[001] preferred orientation of the sheets are developed by tertiary recrystallization.1 The 100 μm thick 3% Si–Fe sheets were prepared via conventional metallurgical processes including melting and casting, hot rolling to 25 mmT at 1200 °C, first cold rolling to 0.5 mmT, intermediate annealing at 800 °C for 30 min, second cold rolling to 0.25 mmT, intermediate annealing at 800 °C for 30 min, final cold rolling to 100 μm and final annealing at 1200 °C for 1 h in a vacuum of 5×10−6 Torr. Among these processes, the cold rolling process is an important one because preferred orientation of the sheets was developed in the process. Nakano et al. reported that there was an optimum cold rolling ratio to get required magnetic properties of the sheets.2 Recently, we found that the reduction rate, i.e., number of passes, as well as reduction ratio affected the preferred orientation and magnetic properties of the sheets. The number of passes in the first cold rolling process was changed from 7 to 60 and B10 values of the final sheets were changed from 1.30 to 1.84 T according to the number of passes. From x-ray experiments, it was found that intensity of (110) peak in the cold rolled and annealed sheets strongly affected the magnetic properties of the final sheets. We will discuss the relationship between the reduction rate and preferred orientation, and magnetic properties of the thin gauged 3% Si–Fe sheets. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365097
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  • 8
    Electronic Resource
    Electronic Resource
    Growth, structure, and magnetic properties of γ-Fe2O3 epitaxial films on MgO (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3253-3256 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-crystal epitaxial thin films of γ-Fe2O3(001) have been grown on MgO(001) using oxygen-plasma-assisted molecular beam epitaxy. The structure and magnetic properties of these films have been characterized by a variety of techniques, including reflection high-energy electron diffraction (RHEED), low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy and x-ray photoelectron/Auger electron diffraction (XPD/AED), vibrating sample magnetometry, and ferromagnetic resonance. Real-time RHEED reveals that the film growth occurs in a layer-by-layer fashion. The γ-Fe2O3(001) film surface exhibits a (1×1) LEED pattern. The growth of γ-Fe2O3 films at 450 °C is accompanied by significant Mg outdiffusion. AED of Mg KLL Auger emission reveals that Mg substitutionally incorporates in the γ-Fe2O3 lattice, occupying the octahedral sites. Magnetic moments are ∼2300 G and ∼4500 G for γ-Fe2O3 films grown at 250 °C and 450 °C, respectively. The high magnetic moment for the films grown at 450 °C could be attributed to the high degree of structural order of the films and Mg substitution at octahedral sites. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364355
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  • 9
    Electronic Resource
    Electronic Resource
    Hg incorporation in CdTe during the growth of HgTe-CdTe superlattices by molecular beam epitaxy (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1545-1547 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HgTe-CdTe superlattices and other microstructures such as single and double barrier tunneling structures are commonly grown by molecular beam epitaxy with the mercury flux continuously on the sample during the growth. This means that some mercury will be incorporated in the CdTe layers. We present here, for the first time, a measurement of the amount of mercury incorporated in thin layers of CdTe. X-ray photoelectron spectroscopy was used to measure the amount of mercury. The amount of mercury was found to be between 3 and 9% for CdTe (111)B, depending on the growth conditions. The amount of mercury was found to increase with mercury flux and to decrease as the substrate temperature was increased. Under the same conditions, it was found that much more mercury was incorporated in the (100) orientation. The type of substrate (CdTe or GaAs) was not found to influence the results. These results indicate that the amount of mercury in the CdTe layers of HgTe-CdTe superlattices is not quite as low as expected from measurements of thick CdTe layers, but it can be low enough that it does not influence significantly the results on the superlattice system in the (111) orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98630
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  • 10
    Electronic Resource
    Electronic Resource
    Electrical properties of Li-doped Hg1−xCdxTe(100) by molecular beam epitaxy (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 2025-2027 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: p-type doping of HgCdTe(100) layers with lithium during growth by molecular beam epitaxy is reported. Hall measurements have been performed on these layers between 300 and 30 K. The Li concentration is found to increase with the Li cell temperature. Li-doped HgCdTe layers are estimated to have very shallow acceptor levels. Acceptor concentrations as high as 8×1018 cm−3 have been achieved. At low doping levels, due to residual donors, layers show compensation. Incorporation coefficient of Li close to 1 and almost 100% electrical efficiency for Li in molecular beam epitaxy HgCdTe layers were observed. However, Li is found to diffuse rapidly in HgCdTe layers grown by molecular beam epitaxy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98281
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