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  • Articles  (180)
  • Blackwell Publishing Ltd  (180)
  • 1995-1999  (180)
  • 1980-1984
  • 1925-1929
  • 1997  (180)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (180)
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  • Articles  (180)
Source
Publisher
Years
  • 1995-1999  (180)
  • 1980-1984
  • 1925-1929
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Topic
  • 101
    Electronic Resource
    Electronic Resource
    THE ROLE OF DYNAMIC STRAIN-AGEING IN THE ENVIRONMENT ASSISTED CRACKING OBSERVED IN PRESSURE VESSEL STEELS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The dynamic strain ageing (DSA) behaviour of A533B Class 1 reactor pressure vessel (RPV) steel, containing 5 ppm of free nitrogen, has been investigated over a wide range of strain rates from 3 × 10−7 to 3−10−3s−1 and temperatures from 20 to 350°C. The DSA was observed within certain temperature ranges at all strain rates tested and its hardening effect in terms of the maximum strengthening stress (s̀p) decreased linearly with the increase of log strain rate. The temperature to stimulate DSA was observed to increase with increasing strain rate. The apparent activation energies of the characteristic strain rates for the onset, and peak of DSA have been determined, and their implications have been discussed. Compared with the available data, a positive effect of free nitrogen content on s̀p has been evaluated. It has been found that the occurrence of susceptible environment assisted cracking (EAC) of A533B steel in high temperature water is co-related to the DSA behaviour. The results suggest that DSA reduces the ductility of RPV steel and its role in enhancing the EAC of RPV steels should not be neglected, in view of the coincidence with susceptibility zones for DSA and EAC in terms of strain rate and temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00396.x
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  • 102
    Electronic Resource
    Electronic Resource
    INTERFACIAL CRACK INITIATION UNDER QUASI-STATIC AND DYNAMIC LOADING CONDITIONS: AN EXPERIMENTAL STUDY (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Interfacial fracture parameters under quasi-static and dynamic loading are examined in a large elastic mismatch bimatenal system. A wide range of remote field loading ratios of shear and tension are considered. The crack tip fields are mapped using the optical method of coherent gradient sensing or CGS and fracture parameters are quantified. Distinctly different crack initiation responses are observed for positive and negative shear stresses acting on the interface. Also, low velocity impact loading experiments are conducted to study the influence of dynamic loading on crack initiation parameters. Dynamic interfacial crack tip fields are recorded using high speed photography and fracture parameters for dynamically loaded stationary cracks are obtained. Measurements suggest significant crack initiation toughness reduction under dynamic loading conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00401.x
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  • 103
    Electronic Resource
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    INFLUENCE OF A NEGATIVE R RATIO ON THE CREEP-FATIGUE BEHAVIOUR OF THE N18 NICKEL BASE SUPERALLOY (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Crack growth rate measurements, performed on smooth specimens during creep-fatigue testing of the N18 nickel base superalloy at 650°C, reveal a strong detrimental effect of the compressive part of the loading cycle. This effect is attributed to the residual stresses in the wake of the crack, which promote early crack opening. A finite element analysis is conducted in order to predict the evolution of the opening stress level as a function of the stress ratio. Good agreement is found between numerical and experimental results. The influence of the constitutive equation of the material on the crack closure level is tested and the effects of kinematic hardening and viscosity are more specifically examined. An engineering simplified method is proposed to determine the opening stress intensity factor as a function of crack length, stress ratio and maximum stress. This method, developed for cracks in smooth specimens, is then applied to small cracks growing from a notch root. Good agreement is found between the results given by the engineering simplified method and the result of the finite element analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00405.x
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  • 104
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    INFORMATION ON CONFERENCES/SEMINARS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01526.x
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  • 105
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    A NEW METHOD FOR THE MEASUREMENT OF MODE II FATIGUE THRESHOLD STRESS INTENSITY FACTOR RANGE ΔKτth (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— In order to evaluate the threshold value ΔKτth for mode II fatigue crack growth, a new measurement method of mode II fatigue crack growth has been developed. This method uses a conventional closed-loop tension—compression fatigue testing machine without additional loading attachments. Mode II fatigue tests for structural steel and rail steel have been carried out. This method has proved successful and has reproduced mode II fatigue fracture surfaces similar to those found in the spalling of industrial steel-making rolls. The crack length during testing was measured by an AC potential method. The relationships between da/dN and ΔKτ and AKτth for several materials have been obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01530.x
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  • 106
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    EFFECT OF CRACK SIZE ON DYNAMIC SCC BEHAVIOUR OF Ti-6A1–4V ALLOY IN 3%NaCl SOLUTION (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Dynamic SCC (DSCC) behaviour of a Ti-6A1–4V alloy has been studied for different microstructures and orientations, in 3%NaCl solution, and the effect of crack size on crack growth behaviour was discussed. Three microstructures were prepared by heat treatment, i.e. two annealed materials (AN705 and AN850) and a solution treatment and ageing (STA) material. Tests were performed at a cyclic frequency of 10 Hz and a stress ratio of 0.9 using CT specimens for long cracks (a≥ 24 mm) and surface-cracked specimens for small cracks (a≥ 0.4 mm). The KDSCC values obtained for small cracks were considerably higher than those for long cracks in all the microstructures, that is a crack size effect in dynamic SCC behaviour was found in the Ti-6A1–4V alloy. For small cracks, the KDSCC values for AN705 and AN850 were the same in the L and T orientations, while the KDSCC value for STA was higher in the L orientation than in the T orientation. The KISCC values were almost the same as, or higher than, the KDSCC values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01528.x
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  • 107
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    MODE I STRESS INTENSITY FACTOR EQUATIONS FOR CRACKS AT NOTCHES AND CAVITIES (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— In this paper, the notch-crack problem is treated in two different ways: if the non-dimensional crack length l/ρ (l= crack length; ρ= notch root radius) is smaller than the transition crack length lT/ρ, it is treated as an edge crack lying within the local stress field around the notch tip; if l/ρ is larger than lT/ρ, the notch-crack is considered as a simple flat crack problem subjected to remote loading, the flat crack size being the sum of notch depth and the real crack length. Based on currently available numerical data, expressions for the transition crack length, lT, and for the geometric factor F=KI/(1.1215Ktσ√πl) are developed for various notch problems for the crack length range l≦lT. It is found that the stress (σyy) normalized by the peak stress (σpeak), σyy/σpeak, for the pre-cracked component is very similar to the geometric factor for short cracks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01493.x
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  • 108
    Electronic Resource
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    STRESS DISTRIBUTIONS FOR V-SHAPED NOTCHES UNDER TENSILE AND BENDING LOADS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— An analytical solution has been proposed recently by the authors to describe, with a unified approach, the stress fields in the neighbourhood of sharp cracks, V-shaped notches and re-entrant corners in plates subjected to remote tensile loading. In the present paper, the above solution is revised and extended, by also determining the relevant displacement fields and the degree of accuracy of the solution for both the longitudinal and transverse stress fields. Afterwards, since the stress field depends on the type of loading, the circumferential principal stress component is modified to account for bending in fatigue life predictions, while the radial principal stress is almost negligible in this case. The analytical results are compared with finite element values obtained for different geometries loaded under tensile or bending conditions, as well as with other closed-form solutions. The new expressions seem to give better stress estimates than the currently available approximate solutions, whether analytical or numerical, when the opening angle of the re-entrant corner is equal to or greater than π/2. Hence they should represent a good starting point to describe stress distributions induced by stress raisers with large and well defined opening angles such as shafts with shoulder fillets, gears and weldments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00314.x
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  • 109
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    LOW CYCLE FATIGUE BEHAVIOUR OF STRUCTURAL STEEL MEMBERS AND CONNECTIONS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— An experimental study was carried out to investigate the low-cycle fatigue behaviour of steel beam and beam-column members, as well as of steel connections, with particular emphasis on beam-to-column joints. Several full-scale specimens were tested, in a multi-specimen testing program, using constant-amplitude displacement histories, to develop a cumulative-damage model. Variable amplitude tests were carried out in order to verify the validity of the proposed model.It is shown that the S-N curves given by codes for high-cycle fatigue can be used to interpret the low-cycle fatigue behaviour of steel members and connections. Miner's rule can be used, together with the previously defined S-N curves and with a cycle counting method to define a unified cumulative damage model valid for both high and low cycle fatigue. A general failure criterion is proposed which considers the actual energy dissipation through plastic deformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00318.x
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  • 110
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    THE FATIGUE BEHAVIOUR OF CRACKED CONCRETE (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Cracks are among the most common flaws in civil engineering structures and, considering the cyclic nature of the variable loading patterns, it is evident that the evaluation of the structure safety factor should consider the stability of cracks when fatigue loading occurs.In the present paper, the behaviour of cracked concrete subjected to cyclic loading is experimentally investigated by means of direct tension tests. In particular, the experiments concern cycles that stay below the critical concrete softening curve.The results show that, depending on the maximum load, damage could occur and that the cyclic envelope curve is very close to the monotonic quasi-static curve. On the basis of the experimental results, an empirical model for subcritical crack growth for cracked concrete under low-cycle fatigue loading is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00323.x
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  • 111
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    INFORMATION ON CONFERENCES/SEMINARS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01538.x
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  • 112
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    CONSIDERATION OF MULTIAXIALITY IN FATIGUE LIFE PREDICTION USING THE CLOSURE CONCEPT (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Based on fracture mechanics a model has been developed for predicting the fatigue lifetime to initiate a crack of technical size (2a∼ .5mm) in engineering components under multiaxial-proportional loading. Using material data determined for uniaxial loading, the model describes and evaluates the elasto-plastic multiaxial notch stresses and strains using the effective range of the J-integral, ΔJeff, as a crack tip parameter. Mean stresses, load sequence effects and various modes of crack propagation due to variable amplitude loading with individual multiaxiality ratios can be explicitly considered. The prediction accuracy of the model is demonstrated using experimental fatigue life data determined with unnotched specimens of FeE460 and A15083 for proportional fully-reversed constant and variable amplitude loading with various multiaxiality ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01542.x
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  • 113
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    HIGH TEMPERATURE SHORT FATIGUE CRACK BEHAVIOUR IN A STAINLESS STEEL (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Continuous low cycle fatigue (LCF) tests with-and without-hold time in push-pull and torsion loading modes and sequential LCF tests in push-pull mode were carried out at 650°C in air on thin tubular specimens of 316 stainless steel; the sequential tests involving pure fatigue (PF) and creep-fatigue (CF) loadings. The growth of short fatigue cracks was studied by taking several replicas from the specimen surface which were subsequently observed under a scanning electron microscope. An analysis was done with respect to both crack density and the orientation of microcracks and macrocrack(s) which led to failure.Crack density was higher on the surface of a CF tested specimen than that of a PF tested specimen. Mainly short cracks oriented at 45° to the specimen axis were observed on a torsion fatigue tested specimen surface. For push-pull specimens the microcracks propagated perpendicular to the specimen axis to form macrocracks that propagated in the same direction. On the other hand, for torsion specimens the microcracks which initially propagated at 45° to the specimen axis linked to form macrocracks oriented parallel and perpendicular to the specimen axis. However, the macrocrack responsible for the final fracture was always oriented parallel to the specimen axis.Cumulative damage was dependent on the type of loading (PF or CF) in the first part of sequential tests. In particular microcracks initiated during an initial damage phase observed under sequential LCF tests in PF were found to be healed by oxide formation during the hold times applied in the subsequent CF loading and this produced a total damage summation significantly larger than one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01544.x
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  • 114
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    FATIGUE CRACK GROWTH BEHAVIOUR OF SM45C STEEL UNDER CYCLIC MODE I WITH SUPERIMPOSED STATIC MODE II LOADINGS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The practical applications of studies related to constant amplitude mode I loading are somewhat limited, since mode I crack growth is often influenced by mode II (sliding mode) or mode III (tearing mode) in industrial situations. For these cases, criteria, rules, and laws have to be worked out and verified by experiments. However, it is very difficult to evaluate mixed-mode fatigue cracking due to crack surface interference, crack closure, crack branching, etc. This paper, which defines the length of a branched crack as an effective slant crack with a length equal to the distance between the two crack tips, explains the influences of crack surface interference by introducing concepts of adhesive wear and scrutinizes some related researches on mixed-mode crack growth behaviour. Additionally an effective stress intensity factor range is described which considers crack closure and crack surface interference and is verified with crack growth tests under mode I fatigue loading and cyclic mode I with a superimposed static mode II loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01548.x
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  • 115
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    FRONT DEVELOPMENT OF A LONG FATIGUE CRACK DURING ITS GROWTH (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— A 3-D elastic-plastic finite element analysis has been developed to simulate the deformation development along the front of a long mode I single edge crack in plates subjected to either monotonic or cyclic loading. Idealisations having both equal and unequal layers through the thickness of the plate were involved. Plane stress and plane strain 2-D finite element analyses were also performed and compared with the present 3-D solutions. The development of the monotonic and cyclic crack tip plastically deformed zones and opening displacements were traced and correlated to accommodate the effect of the plate thickness and the profile of the crack front. A previously developed crack tip deformation parameter was invoked to predict the effect of the specimen thickness on mode I fatigue crack growth and the associated change of crack front profile. Comparison of such a prediction and the experimental findings of the present work reflected the capability of that parameter in modelling fatigue crack growth through the plate thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01529.x
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  • 116
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    SEMI-ELLIPTICAL FATIGUE CRACK GROWTH UNDER ROTATING OR REVERSED BENDING COMBINED WITH STEADY TORSION (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— An analysis of the influence of steady torsion loading on fatigue crack growth rates under rotating or reversed bending is presented. Mixed-mode (I + III) tests were carried out on cylindrical specimens in DIN Ck45k steel and results are compared for two different testing machines: rotary bending and reversed bending obtained by cyclic Mode I (ΔK1) with or without superimposed static Mode III (KIII) loading, simulating the real conditions on power rotor shafts where many failures occur. The growth and shape evolution of semi-elliptical surface cracks, starting from a chordal notch on the cylindrical specimen surface, was measured for several Mode III/ Mode I ratios. Results have shown that the steady Mode III loading superimposed on the cyclic mode I leads to a significant reduction in the crack growth rates. It is suggested that this retardation is related to an increase of plastic zone size near the cylindrical surface in association with the interlocking of rough fracture surfaces, friction and fretting debris, leading to a decrease of the ΔK effective at the crack tip profile due to the “crack closure effect”. This work provides a contribution to a better understanding of crack growth rates under mixed-mode load conditions thereby allowing one to predict remaining lifetimes and to estimate the risks of pre-cracked rotor shafts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01533.x
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  • 117
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    EDITORIAL: A SPANISH SPECIAL ISSUE (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00295.x
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  • 118
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    THE INFLUENCE OF AGEING AT INTERMEDIATE TEMPERATURES ON THE MONOTONIC STRESS-STRAIN BEHAVIOUR AND FRACTURE TOUGHNESS OF A DUPLEX STAINLESS STEEL (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The mechanical behaviour of the duplex stainless steel AISI 329 has been investigated for ageing times up to 15,000 h at 475, 425, 375, 325 and 275°C. The study has concentrated on changes in the monotonic stress-strain behaviour and fracture toughness as a function of ageing temperature and time. It is shown that the tensile behaviour of the steel changes strongly due to ageing. A large increase in yield strength and reductions in ductility and fracture toughness are observed. The deformation hardening behaviour of the aged steel is explained by using a model based on a modified rule of mixtures. Finally it is shown that the higher toughness of aged duplex stainless steels, in comparison with ferritic stainless steels aged under the same ageing conditions, may be associated with the increase in crack growth resistance induced by ductile ligaments of austenite which bridge the crack faces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00298.x
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  • 119
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    K-DOMINANCE CONDITION IN HYDROGEN ASSISTED CRACKING: THE ROLE OF THE FAR FIELD (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— This paper analyses the validity of the fracture mechanics approach to hydrogen assisted cracking in metals on the basis of K-dominance over both the stress-strain state and the accumulation of hydrogen in the fracture process zone. Stress-strain assisted diffusion of hydrogen is considered as the rate controlling factor of hydrogen assisted cracking under sustained or quasi-static loading conditions. The discrepancy in the crack tip zone between the far-field affected diffusion and the asymptotically driven (K-controlled) process is elucidated. The far field (i.e., the stress-strain field which is not K-dominated) is shown to have a minor effect on near-tip hydrogen diffusion. It can only widen the scatter band of crack growth rates in the near-threshold portion of the crack growth kinetics curve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00304.x
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  • 120
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    A CONSTITUTIVE MODEL FOR ELASTIC-PLASTIC DEFORMATION UNDER CYCLIC MULTIAXIAL STRAINING (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The yield criterion is interpreted as defining the metric of the stress space. Hydrostatic stresses correspond to null geodesies. The plastic strain increment represents a normal projection of the increment undergone by a certain scalar function (hardening function) which depends only on the distance between stress points. This establishes a flow rule formally equivalent to the Prandtl-Reuss equations. Consideration of un-loading processes leads to the analysis of equivalent paths and to the definition of a generalized length or separation which provides a new representation of kinematic hardening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00305.x
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  • 121
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    INFORMATION ON CONFERENCES/SEMINARS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00283.x
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  • 122
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    THE EXTENDED COMPACT TENSION SPECIMEN (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— An extended compact tension, EC(T), specimen has been developed for fatigue and fracture testing. The EC(T) specimen exhibits distinct advantages compared to other cracked specimen configurations, i.e., standard compact tension, single-edge crack, and middle-crack tension specimens. Documented herein are stress-intensity factor and compliance expressions for the EC(T) specimen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00287.x
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    THE ANALYSIS OF MECHANICALLY FASTENED REPAIRS AND LAP JOINTS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— A new Dual Boundary Element formulation is presented, which allows for the analysis of mechanically fastened repairs and lap joints. The method requires only the boundaries of the problem to be discretized and the fasteners location is simply defined by a set of internal points.The technique enables the evaluation of fastener forces, sheet stresses and the stress intensity factors which are important parameters for a Damage Tolerance assessment.Examples of applications to repair designs and to a lap joint are presented to demonstrate the robustness of the new formulation that is proposed in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00290.x
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    A METHOD TO REDUCE THE SCATTER IN FATIGUE CRACK GROWTH RATE DATA (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The scatter in experimentally determined fatigue crack growth rates is dependent, in part, on the data reduction process applied to the paired values of crack length and number of cycles recorded in crack growth tests. An additional data reduction process is proposed which replaces the original test data by a smooth curve. Analysis of mid-range growth rate data for Udimet 720 shows that the introduction of this additional data reduction procedure reduces the scatter in the calculated growth rates, increases the effectiveness of Walker's method in accounting for the effects of stress ratio, and leads to more accurate predictions of the experimental crack propagation lives of test specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01492.x
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    INITIAL FRACTURE MECHANISMS IN NICKEL ALLOYED PM STEEL (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Initial fatigue crack propagation mechanisms at near threshold conditions were studied for four nickel-alloyed, powder-metallurgy (PM) steels. Fatigue fracture surfaces were obtained by testing smooth rectangular specimens at 30 Hz and under constant amplitude and zero mean stress conditions. Materials based on Distaloy AE were used in two densities, namely 7.15 and 7.45 g/cm3.All the fracture surfaces were composed of three morphological regions (i) a macrocrack initiation region Rl where cracks propagated preferentially through particles (ii) a macrocrack growth region R2 and (iii) an unstable crack growth region R3 where cracks propagated preferentially between particles. Initial fatigue crack growth, in region R1, was controlled by the propagation of short cracks whose dimensions were comparable to the material microstructure. The subsequent fatigue crack growth in regions R2 and R3 was controlled by ductile rupture between microvoids. Transparticle fracture in region R1 was independent of pore distribution, while interparticle fracture in regions R2 and R3 was dependent on pore distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01490.x
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    ACKNOWLEDGEMENTS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00313.x
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    A PROCEDURE FOR FATIGUE LIFE PREDICTION OF SPOT WELDED JOINTS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The problem of predicting the fatigue life of spot welded joints has not yet been satisfactorily resolved. Several approaches exist, but many of them are difficult to apply to general structures, which are widely different from simple laboratory specimens. A general criterion is proposed in this paper, based on a theoretical extrapolation of the radial stress. The criterion must be used together with a Finite Element model of the joint and so this paper presents the steps required to get the necessary FE data; steps that are also applicable to the case of complex joints. The advantage of the proposed method is its independence of notch effects near the spot-weld edge. The suggested procedure is applied to several specimens of different materials and the results obtained are successfully compared with experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00317.x
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    FATIGUE CRACK GROWTH PREDICTION IN SPECIMENS SIMILAR TO SPUR GEAR TEETH (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The problem of fatigue crack propagation in surface treated specimens similar to gear teeth is analysed. Experimental fatigue tests were carried out on carburized, and carburized and shot peened, specimens. In order to predict crack propagation and to consider the effect of the treatments, different models of the cracked specimens were realized. Two numerical approaches were followed: the finite element method and the weight function technique. Two- and three-dimensional finite element models were constructed, and the stress-intensity factors were evaluated by considering the effect of both the load and the residual stresses due to the treatments. The agreement between these and those obtained through the weight function technique is good. The weight function approach was used directly in the computer software package (which allows crack propagation predictions) and considered the effects of hardness and residual stresses. The comparison between theoretical predictions and experimental results validated the approach followed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00321.x
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    FATIGUE AND FRACTURE IN POLYACETAL RESINS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The fatigue behaviour of polyoxymethylene (POM) of different molar mass (6.1 × 104–1.5 × 105) was studied at stress levels from 35 to 50 MPa (about 55 and 75% of the yield strength, respectively). It was found that cyclic loadings promoted bond breaking of the polymeric chains which considerably reduced the molar mass both in the crack tip region of cracked specimens and in the bulk in the case of uncracked samples. This process probably included the formation of reactive radicals which subsequently favoured the formation of microvoids that weakened the material. The static fracture toughness of fatigued samples decreased on increasing the stress level, the process accelerating as the cyclic loads approached the yield strength. As a result of material modifications during the tests the low molar mass resins did not exhibit stable crack propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00324.x
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    EXPERIMENTAL AND ANALYTICAL ESTIMATES OF FATIGUE CRACK CLOSURE IN AN ALUMINIUM-COPPER ALLOY PART II: A FINITE ELEMENT ANALYSIS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— A numerical investigation of the fatigue crack closure phenomenon has been performed by an elastic-plastic finite element analysis. Computer software was developed to consider many aspects affecting plasticity-induced crack closure. Linear and power-law hardening models are considered in the finite element analysis. The paper presents results from the study carried out on compact tension (CT) coupons at various crack lengths corresponding to different loading conditions. Finally the results of the analysis are compared with the experimental estimates of fatigue crack closure levels obtained from laser interferometry, scanning-electron and transmission-electron fractography presented in Part I of this paper on identical specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01540.x
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    ASSISTED CRACK GROWTH IN MARAGING STEEL WELDS BY GASEOUS HYDROGEN (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The effects of environmental hydrogen content on fatigue crack growth rates (FCGRs) in T-250 maraging steel plates and laser welds were investigated. The influence of ageing treatments on fatigue characteristics of the alloy was also studied. Experimental results revealed that the accelerated FCGRs in the presence of hydrogen were always associated with changes in fracture modes that appear in compact-tension specimens. Even for overaged specimens with excellent resistance to gaseous hydrogen embrittlement, such an acceleration of crack growth in hydrogen could not be avoided. The crack path of underaged specimens in hydrogen was found mainly along prior austenite boundaries for steel plates and along coarse columnar boundaries for welds. In gaseous hydrogen, peak-aged welds exhibited intergranular and quasi-cleavage mixed fracture modes, compared to mainly quasi-clevage for similar aged steel plates. Hence, the enhancement of crack growth in hydrogen was more pronounced for the welds. Overaged welds showed higher FCGRs than the same aged steel plates only in hydrogen and for ΔK values greater than 20MPa√m.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01545.x
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    MECHANISMS AND FATIGUE PERFORMANCE OF TWO STEELS IN CYCLIC TORSION WITH AXIAL STATIC TENSION/COMPRESSION (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Fatigue tests conducted under fully reversed cyclic torsion, with and without superimposed axial static tension/compression loads, were carried out using hour-glass smooth specimens in laboratory air. A high strength spring steel and a 316L stainless steel, were employed to evaluate the effects of mean stress on fatigue performance. Experimental test results show that a biaxial tensile/compressive mean stress had no influence on the cyclic stress-strain response in both materials. However a biaxial tensile mean stress was found to be detrimental to fatigue life of the high strength spring steel but had no effect on the total fatigue life of 316L stainless steel. A compressive mean stress was found to be beneficial to the life of both steels. The fatigue behaviour of the two materials was investigated by experimental observations and the application of theoretical analyses of short crack growth behaviour. Based upon the analysis of surface acetate replicas it has been found that fatigue crack growth is material/stress-state dependent. A biaxial tensile static stress promoted a change in the direction of the Stage I (mode II) crack from the longitudinal direction to a plane normal to the specimen axis in the high strength steel but not in the stainless steel. Consequently a different growth behaviour of Stage I (mode II) cracks was observed for the two materials. The effect of a biaxial mean stress on fatigue crack growth behaviour of the two materials is analysed and described in some detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00286.x
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    RETARDATION AND REPAIR OF FATIGUE CRACKS BY ADHESIVE INFILTRATION (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— This paper presents results which demonstrate that polymeric filler materials, such as low-viscosity epoxies, can be vacuum-infiltrated into fatigue cracks in 7050 aluminium alloy to produce significant levels of fatigue crack retardation. It was found that the main test variable affecting the degree of retardation was the stress level at which the adhesive was introduced and cured. Two infiltrated adhesives were tested.Infiltration at 0% (of the original) peak fatigue stress level produced negligible retardation, while infiltration at the 80% stress level produced about 300% increase in fatigue life for one adhesive and 3000% for the other adhesive. For the highest infiltration stress level both crack-face wedging and adhesion contributed initially to the retardation, but the adhesive component ceased after a crack grew through the adhesive to the original crack tip position. The results are discussed in terms of the applicability of the technique to highly-stressed aircraft components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00292.x
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    INFORMATION ON CONFERENCES/SEMINARS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00271.x
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    MECHANICALLY SHORT CRACK GROWTH FROM NOTCHES IN A MILD STEEL (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Two L-notched specimens made of mild steel (average grain size =30 μm) and having root radii of 0.1 mm and 3 mm, and also a smooth surface specimen were cyclically loaded at different stress levels at R=−1 and at R= 0. A technique based on miniature strain gauges was successfully used to monitor the depth and the opening level of mechanically short cracks of depths from 0.015 mm to 0.5 mm. Three dimensional FEM computations were made to obtain appropriate calibration curves for varying crack aspect ratios and gauge eccentricities as well as notch plastic strain distributions. The fracture of L-notched specimens having a root radius of 0.1 mm was characterized by an early and multiple crack initiation phase (defined by a crack depth of 30 μm), and the short crack growth rates showed a mechanical behaviour different from that of long cracks (large discrepancies at the same ΔK-value, crack deceleration at R=−1 even beyond the notch plastic zone). For smooth surface specimens both the initiation and the propagation of a single short crack represented important fractions of the total life; the short crack growth rates were high and continuously increasing. The notch influence was highly reduced when the stress singularity is truncated by a 3 mm radius. The cracking behaviour was, in several aspects, close to that at smooth surfaces. The evolutions of crack closure were analyzed in each condition (transient decrease and stabilized value of the closure ratio U=ΔKeff/ΔK) and were shown to have a strong influence on short crack growth. Most of the short crack growth rates obtained in the various geometry/loading conditions are well consolidated with LEFM long crack growth rates using the ΔKeff parameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00273.x
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    TWO PARAMETER DESCRIPTION OF CRACK GROWTH INITIATION INCLUDING THICKNESS EFFECTS THROUGH PROBABILISTIC MODELLING (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— The main object of this study is to apply the J-Q model in the transition region with emphasis on the thickness effects and the effects of constraint directly on the lower bound. If only cleavage without prior ductile growth is considered, then in the transition region the thickness effect may be small below a certain thickness. A model for predicting lower bounds from a limited number of data proposed by Stienstra and Anderson has been applied in connection with a J-Q constraint correction. The results are in good agreement with the predictions from a complete statistical analysis. A statistical analysis of the experimental data of cleavage without prior ductile growth, made after a J-Q constraint correction, shows that the latter is an appropriate procedure for evaluating small scale yielding fracture toughness of individual specimens or structures under such conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00277.x
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    CRACK INITIATION AND SMALL FATIGUE CRACK GROWTH BEHAVIOUR OF SQUEEZE-CAST Al-Si ALUMINIUM ALLOYS (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), 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: Abstract— Fatigue strength, crack initiation and small crack growth behaviour in two kinds of squeeze-cast aluminium alloys, AC8A-T6 and AC4C-T6 were investigated using smooth specimens subjected to rotatary-bending fatigue at room temperature. Fatigue resistance of these alloys was almost the same as that of the wrought aluminium alloys because of their fine microstructure and of the decrease in defect size due to squeeze-casting. Fatigue crack initiation sites were at the eutectic silicon particles on the surface of specimens or at internal microporosity in the specimens. Crack initiation life, defined as a crack length of 50 μm on the specimen surface, was successfully estimated from an evaluation of initiation sites using fracture mechanics and the statistics of extrema. Small fatigue crack growth in the two kinds of alloys obeys the relation proposed by Nisitani et al., namely that d(2c)/dN = C(σa/σB)n· (2c), where C is a constant and σB is the ultimate tensile strength. It is pointed out that an improvement in fatigue strength of cast aluminium alloys can be expected by refining the eutectic silicon rather than by an increase in static strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb00281.x
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    Effect of Shear Stress on the Atomistic Structure of a Grain Boundary in Strontium Titanate (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We have studied the atomistic structure of a σ3 (111) grain boundary in strontium titanate by high-resolution transmission electron microscopy (HRTEM). Quantitative evaluation of HRTEM images reveals that shear stresses, which may originate from processing or external loading, have an important effect on the translation state of the two adjacent grains and on the ion positions at the grain boundary. While under low shear stress the boundary exhibits mirror symmetry with respect to the boundary plane and a comparatively large free volume, high shear stress transforms the structure to a “lock-in” configuration, which has no mirror symmetry and a smaller excess volume. These results suggest that internal or external stresses may significantly alter the charge transport properties of SrTiO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03032.x
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    Dislocation Cores and Hardness Polarity of 4H-SiC (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The hardness of opposite basal faces of 4H-SiC single crystals has been measured in the temperature range 25°-1200°3C. A strong hardness anisotropy between the silicon-terminated (0001) and carbon-terminated (0001) faces of this polar crystal has been found. Transmission electron microscopy investigation of the dislocations in the plastic zone of the 1200°3C indentations shows that they lie predominantly on the basal planes parallel to the indented face, and the extra-half planes of the nonscrew dislocations originate from the indented face. It is also found that, when the (0001) Si-terminated face is indented, the dislocations are either widely dissociated, with the width of the stacking fault ribbon much larger than the equilibrium value, or else they are single leading partials, with the corresponding trailing partials absent. In this case, all the leading partials are found to have a silicon core. On the other hand, the dislocations in the plastic zone of the carbon-terminated face are in the form of dissociated dislocations, with the width of the associated stacking fault ribbons appreciably less than the equilibrium value. Moreover, the leading partials of éhese dissociated dislocations have a carbon core. The results indicate that the hardness of the polar basal faces of 4H-SiC at elevated temperatures is partly determined by the nature of the dislocation cores nucleated by the indentation process. It is argued that this is due to the influence of the core on the generation and glide of the leading partial dislocations.
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    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03033.x
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    Edge Stresses in Alumina/Zirconia Laminates (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Using the technique of fluorescence piezospectroscopy, we determine the distribution of thermal residual stresses across the edges of three laminated alumina/zirconia composites. We develop a methodology for separating the measured stress state into microstresses that result from grain-to-grain thermal mismatch and macrostresses that result from lamination-induced thermal mismatch between individual plies. Comparison between the measured edge-stress distributions and those calculated based on a simple force-superposition model shows good agreement, indicating that the laminate system is well approximated as linear elastic. Given the experimental confirmation of significant edge stresses in multi-ply laminates, the possibility of failure initiating at composite edges must be considered in the design of surface-compressed laminate structures with the aim of mediating the detrimental effect of surface flaws.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03031.x
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    Nanostructuring of Laser-Deposited Ti Films by Self-Limited Oxidation (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Local laser-induced oxidation of thin titanium films on glass is shown to be self-limiting due to a decrease in the absorptivity during the reaction. Taking advantage of this confinement, stable writing of transparent oxide line structures narrower than the diffraction-limited focused spot of a continuous wave Ar ion laser (500 nm) has been accomplished. The greatest optical contrast (1:10) with the highest resolution down to 165 nm was observed if the film thickness is of the order of the light absorption length in the metal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03035.x
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    Debonding in Multilayered Composites of Zirconia and LaPO4 (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Multilayered composites consisting of LaPO4 (La-monazite) layers alternating with various ZrO2-based materials were fabricated to investigate whether LaPO4 provides a weakly bonded interface suitable for promoting toughening, as previously observed in the system LaPO4/Al2O3. The following ZrO2-based materials were assessed: Y-ZrO2, Y-ZrO2/Al2O3, Ce-ZrO2, and Ce-ZrO2/Al2O3. Debonding was observed in all cases. The composites containing Y-ZrO2 and Y-ZrO2/Al2O3 were stable, with no reactions, at temperatures up to at least 1600°3C. However, in the composites containing Ce-ZrO2, interdiffusion of Ce and La occurred, resulting in formation of a pyrochlore-like phase and, in the case of the Ce-ZrO2/Al2O3 composite, a (Ce,La)Al11O18 magnetoplumbite phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03038.x
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    Structure and Mechanical Properties of Copper/Niobium Multilayers (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Copper/niobium multilayers prepared by sputtering onto Si substrates with layer thicknesses ranging from 11 to 5000 Å have been characterized by transmission electron microscopy and nanoindentation. The films are strongly textured with {110} close-packed planes of the bcc Nb parallel to the {111} close-packed planes of the fcc Cu and close-packed directions tending to be parallel as well. For the 11 Å layers, the Cu is found to grow pseudomorphically on Nb in the bcc structure. It is thought that, for thicker layers, the bcc Cu loses coherency and transforms martensitically to the fcc phase, thus resulting in the observed Kurdjumov—Sachs orientation relationship. As the layer thickness, d, decreases from 5000 to 500 Å, the hardness increases as d-1/2; i.e., it follows a Hall—Petch relationship so that hardening is due to grain boundaries and interfaces. The slope is the same as in pure Cu, but there is a large intercept which is ascribed to internal stresses and a large dislocation density. As the layer thickness decreases from 100 to 11 Å, the hardness increases as (1/d) ln (0.69d), which is a line tension formulation such as would be expected for Orowan dislocation bowing between the layers. Again there is a large intercept which is ascribed to cutting through the Cu/Nb interfaces. The interfacial energy is calculated to be 0.46 J/m2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03037.x
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    Microstructure Evolution of ZrO2-(Fe2O3, Al2O3) Materials Synthesized with Solution Precursors (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Aqueous Zr-nitrate solutions containing appropriate amounts of Fe(NO3)3·6H2O and Al(NO3)3·6H2O were used to synthesize ZrO2-Fe2O3 compositions (up to 40 mol% Fe2O3) and one ZrO2-Al2O3-Fe2O3 composition. An amorphous phase was produced after pyrolysis, which subsequently crystallized to a single-phase Zr(Fe)O2 solid solution (or Zr(Fe,Al)O2 ss) that appeared cubic by X-ray diffraction, but tetragonal (c/a→ 1) by electron diffraction. The crystallization temperature increased with Fe2O3 content. At higher temperatures, the single phase partitioned to two phases, tetragonal-ZrO2+γ-Fe2O3. The γ- to α-Fe2O3 transformation occurred at still higher temperatures to produce a two-phase microstructure composed of two interpenetrating phases (ZrO2+α-Fe2O3), each with equiaxed grains. This microstructure was relatively stable to grain coarsening, even to temperatures just below the apparent eutectic temperature. With the exception of the lower transition temperatures and the equiaxed grains observed for both phases, these observations are similar to that previously reported for the ZrO2-Al2O3 system. The microstructure development reported here is another example for the synthesis via solution processing that involves diffusion-limited crystallization. Namely, a two-phase material can be produced where the grain size of each can be very small, and can be prevented from growing rapidly at high temperatures due to the constraint of each phase on one another.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03039.x
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  • 145
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    Mechanisms of High-Temperature Creep of Fully Stabilized Zirconia Single Crystals as a Function of the Yttria Content (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: High-temperature creep behavior of yttria fully stabilized zirconia single crystals with various yttria contents in the interval 9.4 ≤x≤ 21 mol% has been studied. The mechanical data have been collected as a function of both the temperature and the yttria concentration. The creep behavior has been explained in terms of a transition between a dislocation viscous glide and a dislocation climb controlled mechanism, making use of a generalized version of a classical model for alloys proposed by Burton. The yttria concentration dependence of the creep rate has been connected with results on cationic diffusivity, with a possible influence of impurities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03036.x
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  • 146
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    A Natural Ceramic/Polymer Layered Composite (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The examination of natural materials at the microscopic and microchemical level from a materials science perspective can occasionally suggest advances in modern materials engineering. The present paper reports on such a case: an analytical study of the detailed structure and composition of sea urchin teeth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03042.x
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  • 147
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    Compression Test and Plastic Strain of α-Al2O3 Single Crystals (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Compression tests of single crystals are analyzed with respect to shear due to the friction at the loaded ends. This simple approach permits an explanation of the features associated with prism plane slip in sapphire (α-Al2O3), i.e., the shape changes of the specimens and the curvature of the glide planes.
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    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03043.x
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  • 148
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    Ferroelasticity of t‘-Zirconia: I, High-Voltage Electron Microscopy Studies of the Microstructure in Polydomain Tetragonal Zirconia (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The microstructure of polydomain tetragonal zirconia (t-ZrO2), i.e., a ZrO2 modification exhibiting ferroelastic behavior, is studied by high-voltage electron microscopy. This material consists of three domain variants of the tetragonal phase with their c-axes nearly orthogonal to each other. Always two variants of these platelike domains are alternately arranged, forming elongated regular colonies. Hence, in both variants the common habit plane of the domains is a {110} twin plane. The colonies are of columnar shape with a longitudinal axis. They are bound by {110} planes, too, which are twin planes for the domains in the contiguous colonies. Owing to their particular structure and the helical arrangement of the adjoining colonies, the material remains coherent and pseudocubic over large macroscopic regions, although it is formed by different tetragonal domains.
    Type of Medium: Electronic Resource
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  • 149
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    Ferroelasticity of t‘-Zirconia: II, In situ Straining in a High-Voltage Electron Microscope (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The ferroelastic deformation of t-ZrO2, the microstructure of which was described in detail in Part I, was investigated by in situ deformation experiments in the high-voltage electron microscope at 1150°3C. During the experiments those two domain variants with their c-axes perpendicular to the [010] tensile direction were transformed into the third one with its c-axis parallel to the tensile direction. The subsequent ‘switching’ of the domains inside the colonies proceeds much faster than the penetration of the transformation front into a neighboring colony. Therefore, the transformed region, exhibiting a unique tetragonal structure and containing residual defects, preferentially expands into the longitudinal directions of the colonies. The transformation of single domains proceeds instantaneously within the time resolution of the video tape recording.
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    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03041.x
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  • 150
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    Agglomeration during the Drying of Fine Silica Powders, Part II: The Role of Particle Solubility (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of particle solubility and the dissolution rate on agglomeration was studied by drying silica and titania particles from aqueous slurries with pH values in the range of 2–12. The agglomerate strength and strength distribution were measured by a calibrated ultrasonic force, and the strength increased as the solubility and dissolution rate increased. Two silica powders of different particle size (60 nm and 500 nm) were studied, and smaller-sized particles formed stronger agglomerates. The drying rate of the powders was varied by using spray drying and tray drying, and slower drying was shown to lead to higher agglomerate strength. The agglomerate strength of titania powder (insoluble in water) was independent of pH, whereas the agglomerate strength of silica was dependent on pH. It was concluded that the solubility and dissolution rate are important parameters that govern the strength of agglomerates.
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  • 151
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    Formation Kinetics of MoSi2 and Mo5Si3 by the Reactive Diffusive Siliciding of Molybdenum (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The formation kinetics of products formed by the reaction between dense molybdenum and vapor-supplied silicon at an activity approximating that of solid silicon under open flowing gas conditions was studied at 1200°3C. An outer MoSi2 layer overlaid the much thinner Mo5Si3 that formed on the molybdenum. Both phases obeyed parabolic growth laws over a 22 h period, having parabolic rate constants of 6.8 times 10-10 cm2/s for the MoSi2 and 1.3 times 10-13 cm2/s for the Mo5Si3 phases. These results were ∼2 orders of magnitude less than prior results, mostly obtained by another processing route. Possible explanations include enhanced growth rates from chemical contamination. Gross distortion and abnormal layer thicknesses at specimen edges and the 159% volume increase during siliciding suggest that the kinetics also are strain dependent.
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    Origin of the Positive Temperature Coefficient of Resistivity Anomaly in the ZnO-NiO System (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An anomalous positive temperature coefficient of resistivity (PTCR) was investigated in the ZnO-NiO system. It was found that the ZnOSS (Zn0.97Ni0.03O) and NiOSS (Ni0.6Zn0.4O) constituent phases of that system exhibit negative temperature coefficient of resistivity (NTCR) character, while their combination shows a PTCR effect with a maximum at 400°3C, which coincides with a large difference in the coefficient of linear thermal expansion between the ZnOSS and NiOSS phases at that temperature. On the basis of the brick wall model microstructure, the PTCR anomaly of this system can be explained. The magnitude of the PTCR effect is governed by the difference in resistivity of the two constituent phases at the temperature where the maximum of the PTCR anomaly occurs. The predicted temperature dependence of the resistance, R(T), of a model microstructure consisting of constituent phases with different grain sizes agrees well with the experimental R(T) of the prepared composite ceramics.
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    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03047.x
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  • 153
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    Effect of Ordering-Induced Domain Boundaries on Low-Loss Ba(Zn1/3Ta2/3)O3-BaZrO3 Perovskite Microwave Dielectrics (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Small substitutions of BaZrO3 into Ba[(Zn,Ni)1/3Ta2/3]O3 are utilized in the commercial preparation of low-loss perovskite microwave dielectrics. The structures of a series of these phases with substitution levels ranging from 1% to 5% BaZrO3 were examined using high-resolution TEM. For ≤ 2.15% BaZrO3 the solid solutions retain the ordered “1:2” structure of the Ba[(Zn,Ni)1/3Ta2/3]O3 end-member but are comprised of small ordered domains whose size decreases as the Zr content is raised. The decrease in the size of the domains parallels a decrease in the processing time required to access a low-loss state. Although for pure Ba[(Zn,Ni)1/3Ta2/3]O3 reductions in the degree of cation order produce a large increase in the dielectric loss, the Zr-substituted ceramics retain a very low loss. We believe the low losses of the 1:2 ceramics are derived from the stabilization of the ordering-induced domain boundaries via the partial segregation of the Zr cations. For substitutions between 3% and 5% BaZrO3 the size of the ordered domains continues to decrease but the system undergoes an abrupt transformation to a cubic “1:1” ordered structure with a doubled perovskite repeat. The structures of these phases have been interpreted using a “random layer” model in which one site is occupied by Ta and the other by a random distribution of Zn, Zr, and the remaining Ta cations, i.e., Ba{[Zn(2-y)/3Ta(1–2y)/3Zry]1/2[Ta1/2]}O3. Although the ordering is confined to nano-sized domains, these ceramics also exhibit low losses, again reflecting the relative stability of the domain boundaries. In this case we believe the low losses reflect the effectiveness of the random layer in stabilizing the anti-phase boundaries.
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  • 154
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    Oxidation of Single Crystals of Hafnium Carbide in a Temperature Range of 600° to 900°3C (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The isothermal oxidation of HfC single crystals with (100) orientation was carried out using an electromicrobalance at temperatures of 600° to 900°3C at an oxygen pressure of 2 to 8 kPa. Nonisothermal oxidation was performed by a simultaneous thermogravimetry—differential thermal analysis—mass spectrometry analysis. A polished cross section of the oxidized crystal was observed by backscattered electron imaging in a scanning electron microscope. Quantitative chemical analysis for Hf, O, and C and their elemental profiles in the HfC and oxide scale was carried out by wavelength dispersive X-ray microanalysis. It was found that the oxide scale consists of two regions, zones 1 and 2, both of which showed the existence of carbon. The carbon content at the middle point of zone 1 was about twice that in zone 2, which contained 7 to 14 at.% carbon. Zone 1 showed an almost compact and pore-free phase; its thickness remained constant (1 to 2 μm) after a prolonged time. The thickness of zone 2 increased linearly with time. The oxidation mechanism including interfacial reaction responsible for the deposition of carbon is discussed.
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    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03048.x
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    Feasibility of Using Cordierite Glass-Ceramics as Tile Glazes (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Basic principles of fabricating tile glazes based on cordieritic glass-ceramics are explained. Glass compositions from the MgO-Al2O3-SiO2 three-component phase diagram have been melted with and without the nucleating agent TiO2. Additionally, a sodium borosilicate glass that is commonly used in the tile glaze industry has been wet milled, together with the previous compositions, to produce a coating slip. Studies are focused on the role of the nucleating agent and glassy formulation in the crystallization of the glass-ceramic system using differential thermal analysis, X-ray diffractometry, and scanning electron microscopy. When added to a borosilicate glass, only one composition is capable of crystallizing cordierite under a fast-firing cycle used for “monoporosa” production. The porosity of the glaze layer is sufficiently low and the crystal size is small to ensure good mechanical and chemical properties. The presence of cordierite crystals in the glaze should enhance abrasion and acid resistance, in comparison to a traditional matte glaze that contains mostly enstatite or diopside crystals.
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    Synthesis of Ba2NaNb5O15 Powders and Thin Films Using Metal Alkoxides (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Transparent and highly oriented Ba2NaNb5O15 (BNN) thin films have been prepared by using metal alkoxides. A homogeneous precursor solution was prepared by the controlled reaction of NaOC2H5, Nb(OC2H5)5, and barium metal. The BNN precursor included a molecular-level mixture of NaNb(OC2H5)6 and Ba[Nb(OC2H5)6]2 in ethanol. The alkoxy-derived powder crystallized to a low-temperature phase, and then transformed to orthorhombic BNN (tungsten bronze) at 600°3C. BNN precursor films on substrates crystallized to orthorhombic BNN at 800°3C via the low-temperature phase. Highly (002) oriented BNN films of tungsten bronze structure were successfully prepared on MgO (100) substrates at 700°3C by using BNN underlayer.
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    Aqueous Processing of Sintered Reaction-Bonded Silicon Nitride: I, Dispersion Properties of Silicon Powder (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An aqueous-based system (Si-Al2O3-Y2O3-Fe2O3) for processing sintered reaction-bonded silicon nitride (SRBSN) was investigated with an emphasis on chemical control of suspension component interactions. Chemical stability and dispersion properties of a commercial silicon powder were characterized using electroacoustic, adsorption isotherm, and rheological measurements. The interactions of silicon with nitriding agent, sintering aids, dispersants, and binder were considered. The effects of pH, electrolyte, aging, particle size, and solids loading were examined. The suspension properties of the silicon powder were influenced by the native oxide film and powder treatment history. The silicon—oxide composite particles exhibit dispersion behavior similar to silica, characterized by a negative surface potential above pH 2. A method to improve the dispersion and homogeneity of suspension components based on the use of quaternary amine dispersants is proposed.
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    Computer Simulation of Grain Growth and Ostwald Ripening in Alumina—Zirconia Two-Phase Composites (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics of grain growth and Ostwald ripening in Al2O3-ZrO2 two-phase composites was systematically investigated using two-dimensional (2-D) computer simulations, based on a diffuse-interface field model. Using average values for the experimentally measured ratios of the grain boundary energies to the interphase boundary energy as the input, the predicted 2-D microstructural features and their evolution are in excellent qualitative agreement with experimental observations on 2-D cross sections of 3-D Al2O3-ZrO2 two-phase composite microstructures. It was found that the coupled grain growth in Al2O3-ZrO2 composites is controlled by long-range diffusion and the average size (Rt) as a function of time (t) follows the power-growth law, Rmt - Rm0=kt with m= 3, which is independent of the initial microstructures and volume fractions of the two phases. The predicted variation of the kinetic coefficient (k) on the volume fraction follows a trend similar to that experimentally measured through the entire range of volume fractions. The scaling of grain size distributions is observed at a given volume fraction, i.e., they are time-invariant in the steady state. However, the characteristics of size distributions vary with the initial microstructures and the volume fractions. The relationship between matrix grain size and second-phase grain size is discussed.
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    Thermally Induced Reversible Coagulation in Ceramic Powder-Polymer Liquid Suspensions (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It was observed that slurries of oxide powders in oxidized polybutene fluids can be caused to change reversibly between fluid, nearly Newtonian behavior and plastic behavior by modest changes in temperature. This phenomenon was believed to result from changes in the dispersion vs association among the particles. The rheological effects of temperature, polymer oxidation, and particle size were observed for 30 vol% slurries of TiO2, Al2O3, and ZrO2 powders in polybutene fluids. Elasticity (in oscillation) and low-shear-rate viscosity (in steady shear) were observed to increase with increasing temperature for TiO2 and Al2O3 particles in oxidized polybutene fluids. This behavior was attributed to the creation of interparticle structures. The attainment of this structure on heating was observed to be inhibited by increased oxidation of the polymer and increased particle size. It was concluded that the adsorption of oxidized molecules from the polymer liquid, along with the high viscosity of the bulk polymer, resulted in suspensions that were metastable against coagulation. Increased temperature resulted in lower viscosities of the liquid, allowing coagulation on a short time scale. The presence of the adsorbed polymer, however, prevented intimate contact among the particles so that the coagulated structure was easily destroyed upon subsequent cooling and shearing.
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    Minimizing Infiltration Times during Isothermal Chemical Vapor Infiltration with Methyltrichlorosilane (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Minimum infiltration times during isothermal chemical vapor infiltration were calculated for the formation of a silicon carbide matrix composite from methyltrichlorosilane (MTS). Several different reaction models were used to describe the SiC deposition kinetics. The results show that the nature of the reaction model has a significant effect on process optimization considerations. It is clear that a simple first-order deposition reaction does not accurately describe the infiltration process, while rate expressions that treat the effect of chlorine-containing byproduct gases provide much more accurate predictions. In theory, much shorter infiltration times can be obtained with precursor chemistries that do not produce Cl-containing gases. The results also provide guidelines for minimizing infiltration times with MTS.
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  • 161
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    High-Temperature Transverse Fracture Toughness of Nicalon-Fiber-Reinforced CAS-II Glass-Ceramic Matrix Composite (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Cracking parallel to the fibers in off-axis plies is usually the initial form of damage in composite laminates. This cracking process has been associated with the (transverse) fracture toughness, defined by the critical strain energy release rate, GIc. The measurement of GIc provides basic information about the transverse crack resistance. In this study, the utility of the double torsion (DT) test technique to determine GIc in a glass-ceramic matrix composite (Nicalon/CAS-II) at temperatures up to 1000°3C has been demonstrated. GIc did decrease moderately with increasing temperature (as does the bulk matrix); however, no evidence of an interphase oxidizing effect on crack growth (parallel to the fibers) could be found. The inevitable misalignment of fibers in the material was not very efficient at bridging the crack in the DT specimens, in contrast to the significant matrix crack interactions with the fibers reported for other geometries such as double cantilever beam and flexure specimens.
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    Reaction Sequence in the Preparation of NiAl2O4 Spinel—Mullite Composites by Sol—Gel (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: NiAl2O4 spinel—mullite composites were prepared by simultaneous replacement of Al by Ti and/or Ni in 3:2 stoichiometric mullite. Specimens having nominal compositions 3(Al2-2xNixTixO3) · 2SiO2 (x= 0, 0.025, 0.05, 0.2) and 3(Al2-xMxO3) · 2SiO2 (M = Ni2+ or Ti4+ and x= 0.05) were synthesized by sol—gel techniques, which provide homogeneous gels in the SiO2-Al2O3 system. Gel structures investigated by infrared (IR) spectroscopy revealed the formation of Al-O-Si bonds in dried gels. The reaction sequence of gel-derived glasses, previously obtained by preheating gels at 750°3C for 3 h, was evaluated by X-ray powder diffraction (XRD) and ultraviolet—visible (UV—vis) spectroscopy. All samples crystallized at around 1000°3C from an amorphous state, but unexpectedly the first crystalline phase was Al-Si spinel in all aluminum-substituted specimens; i.e., a change in the sequence of reaction with respect to the 3:2 stoichiometric mullite was produced. NiAl2O4 spinel was almost simultaneously detected. Two processes of mullite crystallization were observed. The temperature of formation of mullite was the lowest for the higher substituted sample. The microstructure of the final NiAl2O4 spinel—mullite composites found in all Ni-containing samples after annealing for 96 h was examined by scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX), which revealed the presence of small particles of NiAl2O4 spinel dispersed in a mullite matrix. For annealed compositions with the larger Al replacement, i.e., when x= 0.2, a small amount of very small Al2TiO5 particles was also detected by XRD and transmission electron microscopy (TEM).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03054.x
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  • 163
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    Influence of the Oxide Precursors on the Reaction Sequencing and Kinetics in the Yttrium—Barium—Copper—Oxygen System (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The reactions of stoichiometric Y2O3, CuO, and different barium salts (BaCO3, Ba(NO3)2, BaO2, BaCuO2) for forming various compounds in the yttrium—barium—copper—oxygen system (i.e., YBa2Cu3O7–8, BaCuO2, Y2BaCuO5, and Y2Cu2O5) were systematically investigated by thermal analysis and X-ray diffractometry. In a few cases, the relevant activation energies were calculated. The reaction pathway and kinetics were significantly dependent on the physicochemical and thermal stability of the barium precursors, as well as on the crystalline size of the reagent. Binary BaO-CuO phases formed at low temperature (650°-700°3C) when in the presence of easy-to-decompose barium precursors, and then slowly transformed to ternary compounds; in contrast, when barium ions were released at temperatures of 〉900°3C, ternary phases formed directly from the components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03057.x
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  • 164
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    Fiber-Reinforced Ceramic-Matrix Composites with a Polysiloxane/Boron-Derived Matrix (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A ceramic matrix for carbon-fiber-reinforced ceramic-matrix composites (CMCs) has been developed from poly-siloxane/boron mixtures. Complex geometries can be realized by using standard technologies of fiber-reinforced polymer composites. On pyrolysis, the polymer—filler mixture is converted to a ceramic matrix, consisting of silicon carbide, boron carbide, boron nitride, and a silicon oxycarbide (SiOC) glass, without reacting with the carbon fiber. Because of the large volume increase of the boron filler on nitridation (142 vol%), no multiple reinfiltration of the structure is necessary to achieve a dense matrix. Tensile strength and interlaminar shear strength exhibit maxima at a pyrolysis temperature of 1300°3C, where extensive fiber pullout is observed. Thermodynamic calculations have been used to evaluate the theoretical qualitative and quantitative phase compositions at equilibrium. Thermoanalytical (thermogravimetry—mass spectroscopy) and structural analysis (X-ray diffractometry) have shown a satisfying coherence with respect to the condensed phases, whereas deviations have been noted with respect to the composition of the gas phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03058.x
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  • 165
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    Effect of Carbohydrate on the Rheological Parameters of Paste Extrusion (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Carbohydrates are often key components in the formulation of extrusion pastes, yet the reasons for selection are presently empirical. The influence on paste extrusion of various types of carbohydrates, such as starch, dextrin, lactose, and glucose, have been studied and related to their water retention capacities. The bulk yield stress and the surface shear stress both decrease as the moisture content increases; however, the way in which the water that is present interacts with the carbohydrate has an important influence. The behavior of some carbohydrates can be substantially accounted for by a consideration of packing effects; however, dextrin behaves differently. The carbohydrates function not only as a binder but also as a means of retaining the liquid phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03059.x
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  • 166
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    Spherical Indentation and Fracture of Glass Plates (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Spherical indentation of thick and thin glass plates was investigated numerically and experimentally. The energy release rate at the tip of a cone crack was calculated by using finite element techniques and used to investigate the applicability in thick plates of Roesler's law relating the cone crack radius to the indentation load. Indentations of thin glass specimens resting on different substrates were also studied numerically and experimentally. The stresses in the thin specimens were calculated and correlated with the observed failures. On the basis of these results, a crack initiation mechanism map was developed for glass specimens on different substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03060.x
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  • 167
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    Quantitative Characterization of Indentation Crack Path in a Cubic Zirconia—10 vol% Alumina Composite (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Stereological measurements were performed to characterize the indentation crack path in a cubic zirconia—10 vol% alumina (c-ZrO2-10 vol% Al2O3) composite. Cracks were generated using Vickers indentation, and the crack propagation behavior was characterized as a function of the indentation loading/unloading rates. Cracks that were produced by Vickers indentation formed at higher crack velocities as the loading/unloading rates increased. The amount of contact between the crack and the Al2O3 particles increased as the indentation rate decreased. The total number of crack—particle interactions per unit crack length also increased as the indentation rate decreased, because of an increase in the number of particles that were fractured per unit crack length, whereas the number of particles that were debonded remained relatively constant as the indentation rate changed. These results suggest that residual thermal mismatch stresses have predominant control of the crack path at lower crack velocities (low indentation loading/unloading rate), whereas elastic mismatch stresses predominate at higher crack velocities (high indentation loading/unloading rate).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03061.x
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  • 168
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    X-ray Photoemission and Energy Dispersive Spectroscopy of Hydroxyapatite-Coated Titanium (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (X-ray photoemission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls and specimens aged 30 min and 3 h at room temperature in distilled water and 0.2M sodium phosphate buffer (pH 7.2). Each X-ray photoemission cycle consisted of three scans followed by argon sputtering for 10 min for usually 20 cycles, corresponding to a sampling depth of ∼1500 Å. The energy dispersive spectroscopy analysis was on a 110 by 90 μm area for 500 s. The X-ray photoemission results indicated the oxidation effect of water on the titanium (as TiO2) and the effect of the buffer to increase the surface concentration of phosphorus. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03062.x
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  • 169
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    In Situ Reacted Rare-Earth Hexaaluminate Interphases (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A novel in situ reaction between a ceria-doped zirconia interphase coating on Saphikon fibers and an outer alumina coating has resulted in the formation of oriented hexaaluminate platelets which can act as a low fracture energy interface barrier for crack deflection in oxide—oxide ceramic-matrix composites (CMCs). The reaction proceeds only in reducing environments where the reduction of the cerium and zirconium ions to their 3+ valent state causes a destabilization phenomenon consistent with previously reported findings. The diffusion of the cerium from the zirconia into solid solution with the alumina can stabilize the layered hexaaluminate structure. Preferred orientational growth of the hexaaluminate parallel to the coating interface was observed which is the required orientation for enhanced debonding at the fiber/matrix interface in long-fiber-reinforced CMCs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03063.x
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  • 170
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    Strengthening of Alumina by Formation of a Mullite/Glass Layer on the Surface (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A layer composed of mullite and silicate glass was caused to form on the surface of a high-purity alumina ceramic in order to enhance the strength of the material. The layer was formed by exposing the specimens above a bed of SiC platelets at 1400°3C to a flowing H2 atmosphere containing ∼0.1% H2O. A reaction between the SiC platelets and the H2O in the environment resulted in the generation of SiO gas. Some of the SiO gas subsequently reacted with ambient H2O in the atmosphere, forming SiO2“smoke” which was deposited on, and reacted with, the alumina substrate. The strength of the ceramic was significantly improved by the reaction layer, which was found to be comprised of mullite and silicate glass. The increases in strength (about 60% above that of the material in the “as-polished” condition) was attributed to the blunting of surface cracks. A similar strengthening effect was observed in samples of the material which had been ground with a 220-grit diamond abrasive wheel (as had all of the samples) but not polished.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03064.x
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  • 171
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    Differential Negative Resistance and Piezoresistivity in Thin Semiconducting BaTiO3 Ceramic Bars (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thin, semiconducting barium titanate (BaTiO3) ceramic bars, with a diameter of 10 to 20 μm, consisting of single grains joined together in series have been prepared to investigate the piezoresistivity in the materials, which was evaluated from their current (I)-voltage (V) characteristics under the loading condition of various bending stresses. I-V characteristics of single grain boundaries in some of the materials were found to exhibit distinct differential negative resistance (DNR) at room temperature with its feature changing with stress. The DNR appeared on the I-V curves at an electric field of several volts per one grain, and has been confirmed to be connected with the transition of current between two conduction states in the grain boundary region. The obtained results indicate that this phenomenon cannot be interpreted by a rise in the temperature of the materials up to their positive temperature coefficient of resistivity (PTCR) region above the Curie point by Joule heating due to current flow, that is their self-heating effect. This newly observed DNR phenomenon has thus been tentatively interpreted by the morphological change in the ferroelectric domain structure in the vicinity of grain boundaries under mechanical and electric stresses, on an assumption that different configurations of ferroelectric domains yield different conduction states in the grain boundary due to a difference in the degree of surface acceptor charge compensation or the anisotropic carrier mobilities in the crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03065.x
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  • 172
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    Effect of Porosity and Grain Size on the Microwave Dielectric Properties of Sintered Alumina (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The real part of the permittivity (ε) and the tan δ of sintered alumina (Al2O3) at about 9 GHz have been measured. The dielectric properties have been examined as a function of purity, pore volume, and sintered grain size. The tan δ is found to depend very strongly on the pore volume, purity, and grain size. ε is far less sensitive to impurities and grain size. The dependence of ε on porosity can be described by simple mixture models as expected. A model of losses in single crystals cannot be extended easily to these materials where extrinsic factors such as porosity, random crystal orientation, grain boundaries, microcracks, and impurities dominate. These factors have been studied in an attempt to describe the tan δ and ε of sintered polycrystalline alumina. In this work, the tan δ for alumina has been studied in near-theoretical density ranges between 9.1 times 10-5 and 2.4 times 10-5 depending on grain size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03066.x
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  • 173
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    A Discernible Dielectric Aging Effect in the Undoped, N2-H2-Annealed Lead Magnesium Niobate—Lead Titanate Ceramic (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is well known that the undoped Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics, prepared through conventional ceramic processing, present no evident aging effect. In this paper, however, a discernible aging phenomenon was observed in an undoped, N2-H2-annealed ceramic. When this sample was later annealed again in air, this effect became negligible again just like that of a normally prepared PMN—PT ceramic. The valence states of Ti ions, which may be changeable in different annealing atmospheres, were assumed to be responsible for the different degrees of aging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03067.x
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  • 174
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    Model Experiment on Thermodynamic Stability of Retained Intergranular Amorphous Films (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: To test the stability of intergranular amorphous films against crystallization, a model experiment was conducted wherein a thin SiO2 film was deposited on a single-crystal TiO2 substrate, annealed to form a eutectic liquid in equilibrium with the substrate, then quenched and crystallized below the eutectic temperature. This geometry is free of residual stresses and capillary effects proposed by others as kinetic limitations to complete crystallization. Furthermore, using a binary system removes solute rejection barriers to complete crystallization. A remnant amorphous film ∼1.5 nm thick retained at the hetero-interface shows unequivocally that the amorphous film is thermodynamically preferred to a crystal/crystal interface in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03068.x
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  • 175
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    Fast Li+ Ion Conduction in Li2O-Al2O3-TiO2-SiO2-P2O2 Glass-Ceramics (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fast lithium ion conducting glass-ceramics have been successfully prepared from the pseudobinary system 2[Li1+xTi2SixP3-xO2]-AlPO4. The major phase present in the glass-ceramics was LiTi2P3O12 in which Ti4+ ions and P5+ ions were partially replaced by Al3+ ions and Si4+ ions, respectively. Increasing x resulted in a considerable enhancement in conductivity, and in a wide composition range extremely high conductivity over 10-3 S/cm was obtained at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03070.x
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  • 176
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    Three-Dimensional Carbon/Silicon Carbide Composites Prepared by Chemical Vapor Infiltration (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Continuous-carbon-fiber-reinforced silicon carbide composites (C/SiC) were prepared by chemical vapor infiltration in which the preforms were fabricated with the three-dimensional braid method. The mechanical properties and microstructures were investigated. For the composites with no interfacial layer, flexural strength and fracture toughness increased with density of the composites, and the maximum values were 520 MPa and 16.5 MPa·m1/2, respectively. The fracture behavior was dependent on the interfacial bonding between fiber/matrix and fiber bundle/bundle which was determined by the density of the composites. Heat treatment had a significant influence on the mechanical properties and fracture behavior. The composites with pyrolysis interfacial layers exhibited characteristic fracture and relatively low strength (300 MPa).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03069.x
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    Fracture Toughness Evaluation of Small Thin Ceramic Specimens (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A test method to evaluate the fracture toughness, KIC, of thin, small, precracked ceramic specimens is described. The method is applicable for thin plates, wafers, self-supported layers, etc., especially when a large amount of material is not available for testing. The method consists of bonding a small, thin single-edge notched beam on one side of a metallic beam. A stress-free precrack with a square root singularity is achieved when the assembly is deformed in three-point bending.The fracture toughness of a thin, alumina single-edge precracked beam was evaluated experimentally using this method, and compared with that obtained for similar specimens having a 0.3-mm-wide machined notch. Comparison with previously reported fracture toughness values suggests that even a very sharp machined notch overestimates the evaluated fracture toughness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03071.x
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  • 178
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    Dielectric Depression and Dispersion in Electrophoretically Fabricated BaTiO3 Ceramic Films (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dielectric depression and dispersion were observed in BaTiO3 ceramic films fabricated by electrophoretic deposition followed by sintering. The dielectric constants were depressed down to 6800-4600 around the Curie point (TC). The dielectric dispersion occurred above TC. These dielectric properties are attributable to a surface layer formed during sintering. XRD analysis indicated that the surface layer was a hexagonal-like BaTiO3 phase. A mixed solvent of acetylacetone and alcohol employed in the present work may have been responsible for the formation of the surface layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03072.x
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  • 179
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    Characterization of the Cotunnite-Type Phases of Zirconia and Hafnia by Neutron Diffraction and Raman Spectroscopy (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The crystal structures of the cotunnite-type phases (space group, Pnam, Z= 4) of pure zirconia and hafnia prepared under high-temperature, high-pressure conditions in a multianvil device were refined by time-of-flight neutron powder diffraction. The structures of both compounds are very similar and the nine polyhedral metal-oxygen distances range from 2.133(1) to 2.546(1) Å in ZrO2 and from 2.121(1) to 2.535(2) Å in HfO2. The Raman spectra of both phases resemble one another strongly and are consistent with the cotunnite-type structure. These results confirm that ZrO2 and HfO2 undergo transitions to the same phase at high pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03073.x
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    A Symposium in Honor of Professor Arthur H. Heuer's 60th Birthday (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
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    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb19967.x
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